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How does a dual battery system work and do I need one?

Quick answer

A dual battery system adds a second (auxiliary) battery that runs your fridge, lights and other accessories, while the starting battery is kept separate so you can always start the engine. When the engine is running, the auxiliary battery is charged through a voltage sensitive relay (VSR) or a DC-DC charger, and often from solar as well. You probably need one if you camp for more than a night without power and run a 12V fridge, or if you use accessories for long periods with the engine off.

Is this a DIY job?

Difficulty: Medium for a simple under-bonnet VSR system; Pro for DC-DC, lithium, canopy or long cable runs
Time: half a day to a full day
Tools: heavy cable crimper, cable cutter, socket set, multimeter, drill, grommets
Skills: high-current wiring, fusing, battery mounting

Before you wire anything, disconnect the negative terminal of each battery first, and reconnect the negatives last.

How it works

Dual battery system: starting battery, charging device, auxiliary battery and accessories

Starting battery stays connected to the starter and vehicle electrics as normal.
Charging device sits between the two batteries: – a VSR (isolator) links the batteries when it senses the alternator is charging, and separates them when the engine stops; or – a DC-DC charger takes power from the vehicle side and charges the auxiliary battery with a proper multi-stage charge profile. Many also accept solar input. (see DC-DC charger or VSR isolator: which do I need?)
Auxiliary battery (usually deep-cycle AGM or lithium) powers your accessories.
Accessories (fridge, lights, USB, inverter) are wired to the auxiliary battery, each with its own fuse.
Solar (optional) charges the auxiliary battery through a regulator, or through a DC-DC charger with a built-in solar input.

Step by step: planning a system

Work out your daily power use. Add up what your fridge and other accessories draw over a day, in amp-hours (Ah). The fridge maker’s data is a starting point. (see How much solar do I need for my caravan?)
Choose the battery type and size. Deep-cycle AGM is heavier and you can only use part of its rated capacity without shortening its life. Lithium (LiFePO4) is lighter and lets you use more of its capacity, but costs more and needs a compatible charger and a cooler location.
Choose the location. Under the bonnet (short cables, but hot), in a canopy, tray or cargo area (cooler, but longer cables), or in a caravan. Lithium batteries generally don’t suit hot engine bays: heat shortens their life, and some makers say not to fit them there at all.
Choose the charging device. A VSR suits matching lead-acid batteries close together on vehicles with a conventional alternator. A DC-DC charger suits smart alternators, lithium batteries, long cable runs and solar.
Size the cables and fuses. The link cable between the batteries carries high current and needs to be heavy, with a fuse or circuit breaker near each battery. (see What size cable do I need for my 12V accessory?)
Mount the battery securely. Use a proper tray or box with a hold-down that won’t let the battery move in a crash or on corrugations.
Wire accessories to the auxiliary battery with individual fuses, ideally through a fuse block, and a low-voltage cut-off where needed.
Test the system. With the engine running, check the auxiliary battery is charging. With the engine off, check accessories run from the auxiliary battery and the starting battery stays isolated.

Specs table

VSR vs DC-DC at a glance

	VSR (isolator)	DC-DC charger
How it charges	Connects auxiliary battery straight to the vehicle system when charging	Converts vehicle power into a multi-stage charge for the auxiliary battery
Smart (variable-voltage) alternators	Often won’t fully charge the auxiliary battery	Designed to cope
Lithium auxiliary battery	Generally not suitable	Common choice (with a lithium charge profile)
Long cable runs (canopy, caravan)	Voltage drop reduces charging	Compensates better
Solar input	Needs a separate regulator	Many have one built in
Cost	Lower	Higher

What you’ll need

deep cycle battery AGM or lithium battery 12V
voltage sensitive relay or DC-DC charger
battery tray or battery box
heavy duty single core auto cable / twin core auto cable
circuit breaker or MIDI fuse holder (one near each battery)
cable lugs and adhesive heat shrink
fuse block
battery monitor (optional)

When to call an auto electrician

Your vehicle has a smart alternator, stop-start or a battery management system.
You’re fitting a lithium battery or a battery in a canopy, tray or caravan.
You need to run heavy cable through the firewall or along the chassis.
You’re adding an inverter or 240V outlets. Fixed 240V wiring needs a licensed electrician. (see How do I choose and install an inverter?)
The auxiliary battery isn’t charging, or the starting battery goes flat when camping.

Need an auto electrician? Find local auto electricians and mobile services in your city.

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Sources

REDARC, “The truth about alternators” – smart alternators vary their output; a simple isolator won’t charge an auxiliary battery properly from one; DC-DC charger recommended; solar and vehicle charging together. https://redarcelectronics.com/blogs/blog/the-truth-about-alternators (checked October 2026)
REDARC, “BCDC v DCDC dual battery chargers” – vehicles with variable-voltage alternators need a DC-DC charger; lithium charge profiles; solar input; isolator suits traditional alternators. https://www.redarcelectronics.com/au/discover/bcdc-v-dcdc-dual-battery-chargers/ (checked October 2026)
REDARC, “The REDARC call log: lithium battery FAQs” – lithium batteries aren’t designed for engine bays; near-full usable capacity compared with AGM. https://www.redarcelectronics.com/au/discover/the-redarc-call-log-lithium-battery-faqs/ (checked October 2026)
Solar4RVs, “Understanding cable size types: mm, mm², B&S, AWG” – cable sizing for DC-DC chargers and battery links. https://www.solar4rvs.com.au/buying/buyer-guides/understanding-cable-size-types-mm-mm2-b_s-awg/ (checked October 2026)

26 October 2026

What is a smart alternator and how does it affect accessories?

Quick answer

A smart alternator (also called a variable-voltage or computer-controlled alternator) is controlled by the engine computer, which raises and lowers its output to save fuel and cut emissions. It often charges at a low voltage while you cruise and charges harder when you lift off the accelerator or brake. That’s fine for the starting battery, but it means an auxiliary or caravan battery joined by a simple relay (VSR) often won’t charge fully, so most installers use a DC-DC charger on vehicles with a smart alternator.

Is this a DIY job?

Difficulty: Easy to identify; Pro to wire accessories correctly
Time: 15 to 20 minutes to check
Tools: digital multimeter, torch, owner’s manual
Skills: basic use of a multimeter

Anyone can check for the signs below. Wiring a dual battery or caravan charging system to a smart alternator vehicle is best left to an auto electrician, because the battery sensor and the vehicle’s computer have to be wired around correctly.

How a smart alternator works

A conventional alternator has its own regulator that holds the charging voltage fairly steady whenever the engine runs. A smart alternator takes its orders from the vehicle’s computer instead. The computer watches the battery (usually through a sensor clipped to the battery negative terminal) and decides how hard the alternator should work.

When the battery is well charged, the computer turns the alternator down, so the engine has less load and uses less fuel. When you lift off the accelerator or brake, it turns the alternator up and uses the car’s momentum to recharge the battery. Smart alternators started appearing around 2010 and were common in new vehicles by about 2015.

Step by step: how to tell if you have one

Check the battery negative terminal. Look for a small electronic module with a plug and wires, clamped to the negative post. That’s the battery sensor. It’s a strong sign of a smart charging system. Don’t remove it.
Look for other clues. Stop-start, or a note in the owner’s manual about battery “registration” or a battery management system, also point to smart charging.
Start from cold. Ideally the car has sat overnight. Switch off the fan, radio, lights and other loads.
Measure at startup. Set the multimeter to DC volts and measure across the battery terminals with the engine running. Expect about 14 V or a little more at first.
Measure again after 5 to 10 minutes of idling or driving. If it has dropped to about 12.5 V, it’s very likely a smart alternator. A conventional alternator usually stays between about 12.8 and 14.4 V.
Confirm with the vehicle maker or a workshop scan tool if the readings are unclear. There’s no complete published list of vehicles with smart alternators. (see How do I know if my alternator needs replacing?)

How it affects accessories

VSRs (voltage sensitive relays): A VSR connects the second battery when it sees charging voltage. If the alternator is sitting low, the VSR may not switch on, or the auxiliary battery only gets a partial charge.
Caravan and camper batteries: The voltage is already low at the alternator, and then more is lost along the long cable to the van. The result is a van battery or fridge that barely charges while you tow. (see Why isn’t my caravan battery or fridge charging while towing?)
DC-DC chargers: A DC-DC charger boosts and controls the charge for the auxiliary battery, so it copes with a low or changing input. Many need an ignition or “D+” signal wire on smart alternator vehicles so they know the engine is running. (see DC-DC charger or VSR isolator: which do I need?)
The battery sensor: Many smart alternator vehicles have a sensor on the battery’s negative terminal that measures current flowing in and out of the starting battery. Whatever you fit, a good, solid earth is essential. Check the charger and vehicle instructions for where accessory earths should connect: many say to use a body or chassis earth point rather than stacking cables straight onto the negative post, so the sensor still sees the real current. Getting this wrong can confuse the charging system, and at least one DC-DC charger maker warns it can blow the charger’s input fuses.
Replacing the battery: RACV notes that some vehicles with a battery management system need the new battery registered with the system. This is done with a scan tool. (see What’s the difference between flooded, EFB, AGM and lithium car batteries?)

Specs table

Typical battery voltage with the engine running

Reading	Conventional alternator	Smart alternator
Just after a cold start	About 14 V	About 14 V or a little more
After 5 to 10 minutes, loads off	Stays about 12.8 to 14.4 V	Can drop to about 12.5 V
Full range you might see while driving	Fairly steady	About 12.3 V to 15 V

Readings vary between vehicles and conditions. A low reading on a smart alternator vehicle doesn’t by itself mean the alternator is faulty.

Effect on common accessory setups

Setup	With a smart alternator
VSR joining two batteries under the bonnet	Often doesn’t charge the second battery fully
Caravan battery charged through pin 8 of a 12-pin plug	Usually poor charging: low voltage plus long thin cable
DC-DC charger near the auxiliary battery	Designed to cope; may need an ignition or D+ wire
Lithium auxiliary battery	DC-DC charger with a lithium profile

What you’ll need

digital multimeter (to check)
DC-DC charger (if you’re charging an auxiliary or caravan battery)
heavy duty single core auto cable or twin core auto cable
circuit breaker / MIDI fuse holder (one at each end of the charging cable)

When to call an auto electrician

You’re adding a dual battery, DC-DC charger or caravan charging to a vehicle with a smart alternator.
Your vehicle has a battery sensor, stop-start or battery management, and you’re not sure where accessory wiring and earths should connect.
The auxiliary battery isn’t charging after a day’s driving, or a warning light appeared after accessories were fitted.
You’ve replaced the starting battery and the vehicle now shows warnings or stop-start has stopped working.

Need an auto electrician? Find local auto electricians and mobile services in your city.

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Sources

CarsGuide, “Vehicles fitted with a smart alternator in Australia” – how smart alternators work; first appeared around 2010 and common by 2015; voltage test method (about 14 V at start; about 12.5 V after 5 to 10 minutes indicates smart; 12.8 to 14.4 V indicates fixed voltage); effect on second batteries; no definitive list of vehicles. https://carsguide.com.au/car-advice/vehicles-fitted-with-a-smart-alternator-in-australia-97156 (checked October 2026)
Hema Maps, “Smart alternators” – smart alternator output can range between 12.3 V and 15 V; reduces voltage to cut emissions; VSRs and secondary batteries. https://www.hemamaps.com/blogs/hema-maps-gear/alternator (checked October 2026)
Redarc, “How do I know if I have a variable voltage alternator?” – battery sensor usually on the battery negative terminal; also called smart or computer-controlled alternators. https://redarcelectronics.com/us/resources/chargers-isolators-faqs/how-to-identify-smart-alternator/ (checked October 2026)
Enerdrive, EN3DC30 installation guide addendum V2 – on smart alternator vehicles the negative cable must connect to the vehicle side of the battery sense module; otherwise the charger’s input fuses can blow. https://www.mygenerator.com.au/assets/images/resource/pdf/EN3DC30-Install-guide-Addendum-V2.pdf (checked October 2026)
Solar4RVs, “Trouble shooting and fault finding problems on caravans” – DC-DC chargers on variable-voltage alternators may need the ignition or D+ wire connected. https://www.solar4rvs.com.au/blogs/buyer-guides/trouble-shooting-fault-finding-problems-on-caravan (checked October 2026)
RACV, “Car battery replacement” – some vehicles with battery management systems require new batteries to be registered with the system. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)

26 October 2026

How do I test my car battery?

Quick answer

Let the car sit overnight with everything off, set a multimeter to DC volts and put the red probe on the positive post and the black probe on the negative: about 12.6 V means fully charged, 12.4 V is about 75%, and anything below that is discharged and should be charged before you judge the battery. Voltage only tells you the state of charge, not the battery’s health, so if a fully charged battery still struggles, have it load tested or checked with an electronic battery tester. Testing straight after driving or charging gives a falsely high reading.

Is this a DIY job?

Difficulty: Easy
Time: 5 minutes for a voltage check; overnight wait for an accurate reading
Tools: digital multimeter, safety glasses, gloves; optionally a hand-held electronic battery tester
Skills: basic use of a multimeter

Anyone can do a voltage check. A proper health test needs a load tester or an electronic battery tester. Many auto electricians, battery outlets and roadside services will run one for you. If the battery is swollen, cracked, leaking or smells of rotten eggs, don’t test it: leave it alone and get help.

Three ways to test a battery

Test	What it tells you	Who can do it
Resting voltage (multimeter)	State of charge only	Anyone with a multimeter
Electronic tester (conductance or impedance)	Estimated cold cranking amps (CCA) and a pass/replace result	Anyone with a tester; most workshops
Load test (carbon pile or load tester)	Whether the battery holds its voltage under a heavy current draw	Usually a workshop

None of these measures a battery’s remaining capacity on its own. A battery can pass a CCA test and still fail soon after because its capacity has faded. That’s why a battery with a history of going flat is worth a full check even if one test looks fine.

Step by step

Resting voltage test (multimeter)

Let the battery rest. Park the car overnight with the engine off and everything switched off. Driving or charging leaves a “surface charge” that makes the voltage read high for several hours.
Look before you touch. Safety glasses on. Check the case for swelling, cracks, leaks or heavy corrosion. If you find any of these, stop.
Set the meter. Black lead in COM, red lead in V/Ω, dial on DC volts (20 V range on a manual meter). (see How do I use a multimeter on my car?)
Measure. Red probe on the positive (+) post, black probe on the negative (−) post. Touch the lead posts or clamp bolts, not the plastic covers.
Compare with the table below. At 12.6 V the battery is fully charged. At 12.4 V or less, charge it fully with a battery charger, let it rest again, and retest before you decide anything. (see How do I charge a car battery with a battery charger?)

Cranking check (multimeter and a helper)

Keep clear of moving parts. Hands, hair, clothing and leads away from the belt and fan.
Watch the voltage while a helper starts the engine. Keep the probes on the posts (alligator clips make this easier). For comparison, the formal battery load test passes a battery that holds at least 9.6 V under a heavy load for 15 seconds (at 10°C or warmer). If the voltage falls well below that while cranking, or the engine cranks slowly, the battery is weak or there’s a connection or starter problem, and a proper load test or electronic battery test will confirm which. (see Is it my starter motor or my battery?)

Charging check (engine running)

With the engine idling and accessories off, measure across the battery again. Most conventional charging systems read roughly 13.5 to 14.8 V. A reading at or near the resting voltage means the battery isn’t being charged, so a “dead battery” may really be a charging fault. Smart charging systems can read lower at times. (see How do I know if my alternator needs replacing?)

Electronic battery tester

Charge first if needed. Electronic testers give unreliable results on a battery that’s well below full charge. Battery testing guidance suggests at least 70% state of charge for a conductance test.
Connect the tester’s clamps red to positive, black to negative, directly on the battery posts.
Enter the battery details. Select the battery type (flooded, EFB, AGM) and the CCA rating and standard printed on the battery label. Entering the wrong figure gives a wrong result.
Read the result. Most testers give a measured CCA, a state-of-charge figure and a verdict such as “good”, “charge and retest” or “replace”. If it says “charge and retest”, charge it fully, let it rest and test again before buying a battery.

Load test

Leave this one to a workshop unless you own a load tester. The standard carbon pile test draws half the battery’s rated CCA for 15 seconds at 10°C or warmer. A battery that stays above 9.6 V passes. Load testers get hot and can spark, and the battery must be at least 70% charged first.

If the battery fails

Check the cause before you replace it. A battery that keeps going flat might be fine and the real fault might be a drain or a charging problem. (see Why does my car battery keep going flat?)
Replace with the correct type. Stop-start cars need an AGM or EFB battery, and some cars need the new battery registered to the car’s computer. If you do replace it yourself, disconnect the negative terminal first and reconnect it last. (see How do I replace a car battery?)

Specs table

Resting voltage and state of charge (standard 12V lead-acid battery, rested)

Voltage	State of charge	What to do
12.6 V or more	About 100%	Fully charged
12.4 V	About 75%	Charge it; RACV treats anything under 12.4 V as discharged
12.2 V	About 50%	Charge it, then retest
12.0 V	About 25%	Flat: charge it, then retest
11.9 V or less	About 0%	Dead flat: charge and retest; may need replacing

The US battery industry’s standard table (24-hour rest, 26°C) gives almost the same figures. AGM batteries read slightly higher when full, and cold lowers the reading. A battery tested straight after driving or charging can read well above these figures because of surface charge, which settles after a few hours’ rest. Check the battery maker’s figure for your battery.

Other test figures

Test	Figure	Source note
Running (charging) voltage	About 13.5 to 14.8 V	Conventional charging; smart systems vary
Load test (carbon pile)	Half rated CCA for 15 s; pass if above 9.6 V	Battery at 70% charge or more, 10°C or warmer
Cold cranking amps (CCA) rating	Amps the battery delivers for 30 s at −18°C while staying at or above 7.2 V	SAE J537 definition
Electronic tester	Battery at 70% charge or more	Readings drop as charge falls
Replacement guide	Replace when CCA drops to 50% of rating	Heat-failed batteries; CCA doesn’t show capacity loss

What you’ll need

digital multimeter
battery tester (electronic conductance tester for 12V batteries)
smart battery charger (to charge before retesting)
battery terminal brush (clean posts give accurate readings)
safety glasses and nitrile gloves

When to call an auto electrician

The battery is swollen, cracked, leaking, very hot or smells of rotten eggs.
The battery tests good but keeps going flat (likely a drain or charging fault).
The charging voltage is outside the normal range, or the battery warning light is on.
Your car needs battery registration or coding after a replacement.
The car is a hybrid or EV. Its 12V battery can be tested, but the high-voltage battery and its wiring are professional-only.

Need an auto electrician? Find local auto electricians and mobile services in your city.

Find an auto electrician near you

Sources

RACV, “Car battery guide: how they work, when to replace them, and how to jump-start” – multimeter on 20 V DC after the car has been off overnight; voltage vs state-of-charge guide; “anything under 12.4 V is considered discharged”; lifespan of three to five years (lead-acid) and five to seven years (AGM). https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
NRMA, “Tips from an NRMA patrol: car battery maintenance” – magic eye shows one of six cells only; newer cars can fail with little warning. https://www.mynrma.com.au/open-road/advice-and-how-to/car-maintenance/tips-from-a-patrol-batteries (checked October 2026)
NRMA, “Common car battery myths” – CCA definition (30 seconds at −17.8°C, 12V battery). https://www.mynrma.com.au/open-road/advice-and-how-to/car-maintenance/car-battery-myths (checked October 2026)
Battery University, “BU-903: How to measure state of charge” – rest at least four hours (24 hours recommended); surface charge; BCI open-circuit voltage table at 26°C; AGM reads slightly higher; temperature effect. https://batteryuniversity.com/article/how-to-measure-state-of-charge (checked October 2026)
Battery University, “BU-902a: How to measure CCA” – SAE J537 (−18°C, 30 s, 7.2 V); carbon pile test at half CCA for 15 s above 9.6 V at 10°C or higher; 70% state of charge for load and conductance tests. https://batteryuniversity.com/article/bu-902a-how-to-measure-cca (checked October 2026)
Battery University, “BU-905a: Testing starter batteries in vehicles” – CCA testers can’t detect low capacity; replace when CCA drops to 50%. https://batteryuniversity.com/article/bu-905a-testing-starter-batteries-in-vehicles (checked October 2026)
JS Alternators, “How to test your alternator: complete guide” – running voltage about 13.5–14.8 V on conventional systems; smart charging reads differently. https://js-alternators.com/blogs/blog/how-to-test-alternator (checked October 2026)
RACV, “Mobile car battery replacement” – some vehicles have battery management systems that require new batteries to be registered. https://www.racv.com.au/cars-transport/vehicle-maintenance/car-batteries.html (checked October 2026)
Banner Batteries, “Battery sensor – application and function” – don’t fit a conventional battery to a start-stop vehicle that uses AGM or EFB. https://www.bannerbatterien.com/en/Battery-knowledge/20-Battery-sensor-%E2%80%93-application-and-function (checked October 2026)

26 October 2026

Why isn’t my caravan battery or fridge charging while towing?

Quick answer

Usually because too little voltage reaches the van. The cable from the tow vehicle is long, often too thin (the charging pins on a 12-pin plug are commonly wired with about 2.5 mm² cable), and many newer vehicles have smart alternators that lower their voltage while you drive. Check fuses at both ends, the plug connections and the earth return first. The lasting fix is usually heavy twin cable through an Anderson plug to a DC-DC charger mounted near the caravan battery.

Is this a DIY job?

Difficulty: Medium to diagnose; Pro to rewire on modern vehicles
Time: 30 to 60 minutes to check; half a day or more to rewire
Tools: digital multimeter, a helper, trailer circuit tester, torch
Skills: measuring voltage with a multimeter

The checks below are safe for most people with a multimeter. Running new heavy cable, fitting a DC-DC charger or wiring around a smart alternator’s battery sensor is a job for an auto electrician.

Step by step: the checks

Dual battery system overview showing where the DC-DC charger sits

Start safely. Engine off, van unplugged from mains power, and nothing loose near the batteries.
Work out how your van is meant to charge. Look for a 12-pin plug, a separate Anderson plug, or both. Check whether there’s a DC-DC charger in the van or in the vehicle. If the van only has a 7-pin plug, it has no proper charging circuit from the vehicle.
Make sure nothing is wired to pin 2. On Australian 7-pin and 12-pin plugs, pin 2 is reversing lights. It’s only live when the vehicle is in reverse (if at all), so it can’t charge a battery. Auxiliary power should never be wired to it. (see What’s the difference between 7-pin flat, 7-pin round and 12-pin trailer plugs?)
Check the fuses or circuit breakers at both ends. There should be one near the vehicle’s battery and one near the van battery or charger input. A tripped breaker or blown fuse at either end stops charging. (see How do I check and replace a blown fuse?)
Inspect the plugs. Look at the Anderson plug contacts and the 12-pin pins for corrosion, burn marks, loose crimps or bent pins. A plug that’s discoloured or melted means a high-resistance connection: stop using it and get it repaired. (see How do I wire an Anderson plug?)
Measure voltage at the vehicle battery. Engine running, van connected. This is point A. Write it down.
Measure voltage at the van end with the charger working. At the charger’s input (point B), or at the van battery if there’s no charger. A helper can keep the engine running. A big difference between A and B means voltage drop in the cable, connections or earth. On a DC-DC charger, the input voltage should be close to the vehicle battery voltage.
Check the earth return. The charging current has to come back to the vehicle battery. If it returns through a thin wire, a single 12-pin earth pin or the towball and chassis, much of the voltage can be lost there. The negative should be the same size as the positive.
Check for a smart alternator. If point A drops to around 12.5 V after a few minutes of driving, the vehicle probably has a smart alternator. A plain cable or relay won’t charge the van well from that. (see What is a smart alternator and how does it affect accessories?)
If you have a DC-DC charger, check its signals and settings. Many need an ignition or “D+” wire to switch on with a smart alternator. Check the status lights and that it’s set for your battery type (lithium needs a lithium profile).
Check the fridge circuit separately. The most common caravan fridge is a three-way fridge that runs on gas, 12V or 240V. On 12V it’s meant for use while towing, and it draws more current than most other loads in the van, so it needs its own heavy, fused feed from the tow vehicle and drops off quickly if the cable is thin. If the fridge isn’t cooling on the road, check it’s switched to 12V, then check its fuse and feed. When parked, switch it to gas or 240V.
Decide on the fix. If the checks show big voltage drop, thin cable or a smart alternator, the usual fix is heavy twin cable and an Anderson plug to a DC-DC charger near the van battery, fused at both ends. (see DC-DC charger or VSR isolator: which do I need?)

Specs table

Charging-related pins on Australian trailer plugs

Plug	Pin	Function	Colour	Use for charging?
7-pin flat or round	2	Reversing lights	Black	No
12-pin flat	2	Reversing lights	Black	No
12-pin flat	8	Permanent 12V	Orange	Yes, if wired with heavy cable and fused
12-pin flat	9	Ignition-switched 12V or auxiliary	Pink	Sometimes (often used for a fridge or charger signal)
12-pin flat	10	Second earth	White	Return path for pins 8 and 9
Anderson SB50	–	Positive and negative, heavy contacts	–	Yes: 50 A rating with contacts to suit the cable

A common 12-pin wiring recommendation for pins 8, 9 and 10 is 2.5 mm² cable, which is thin for a long charging run. Pins 8 and 9 are used differently by different installers: always test what your vehicle and van actually carry.

Example: voltage lost in the cable, 10 m one-way run (20 m out and back)

Cable (copper area)	At 10 A	At 20 A
2.5 mm²	1.38 V	2.75 V
6mm auto (4.59 mm²)	0.75 V	1.50 V
8 B&S (8.37 mm²)	0.41 V	0.82 V
6 B&S (13.3 mm²)	0.26 V	0.52 V
4 B&S (21.2 mm²)	0.16 V	0.32 V

How this is worked out: voltage drop = current × resistance of the full loop, using copper at about 0.0172 ohm per metre for 1 mm² at 20°C. Plugs, crimps, fuses and a chassis earth add more loss, and hot cable loses a little more. The 10 m run is only an example: measure your own and use the full table in our cable size guide. (see What size cable do I need for my 12V accessory?)

To put that in context: a fully charged lead-acid battery rests at about 12.6 V, and a conventional alternator charges at roughly 13.5 to 14.8 V. Lose 1.5 V in the cable and there’s little or nothing left to push charge into the van battery, even before a smart alternator lowers its output.

What you’ll need

DC-DC charger (with a lithium setting if your van battery is lithium)
twin core auto cable or heavy duty single core auto cable (6 B&S is common for this run, and is the largest size a standard 50 A Anderson contact accepts)
Anderson plug 50A with contacts to suit the cable, plus Anderson plug mounting bracket and Anderson plug cover
circuit breaker or MIDI fuse holder (one at each end)
cable lugs and adhesive heat shrink
digital multimeter and trailer circuit tester

Why fuse both ends?

The charging cable connects two batteries: the vehicle’s at one end and the van’s at the other. If the cable shorts to the chassis anywhere along its length, either battery can feed the short. A fuse or circuit breaker close to each battery protects the cable from both directions. Size each one to protect the cable, not just to suit the charger.

When to call an auto electrician

Your vehicle has a smart alternator, a battery sensor, stop-start or battery management.
You need new cable run the length of the vehicle, through the chassis or past airbag zones.
You’re fitting a DC-DC charger, lithium battery, solar or an inverter in the van.
A plug, cable or terminal is getting hot, discoloured or has melted.
You want 240V wiring changed in the van. Fixed 240V wiring is for a licensed electrician only.

Need an auto electrician? Find local auto electricians and mobile services in your city.

Find an auto electrician near you

Sources

Wikipedia, “Trailer connectors in Australia” – pin 2 is reversing lights and auxiliary power should never be wired to it; 12-pin pins 8 (permanent +12V, orange), 9 (ignition +12V, pink) and 10 (earth, white) with a recommended cross-section of 2.5 mm². https://en.wikipedia.org/wiki/Trailer_connectors_in_Australia (checked October 2026)
ExplorOz, “Trailer wiring diagrams” – 7-pin and 12-pin pin functions and colours. https://www.exploroz.com/vehicle/electrics/trailerwiringdiagrams.aspx (checked October 2026)
Solar4RVs, “Trouble shooting and fault finding problems on caravans” – check the Anderson connection and fusing; DC-DC input voltage should be close to the starter battery; large difference means cable too small or high resistance; ignition or D+ wire on variable-voltage alternators. https://www.solar4rvs.com.au/blogs/buyer-guides/trouble-shooting-fault-finding-problems-on-caravan (checked October 2026)
Caravan World, “Tech: DC-DC battery management” (Collyn Rivers) – voltage drop in long thin cable; mount the DC-DC unit close to the auxiliary battery; heavy supply cable (at least 13.5 mm²) and an Anderson connector. https://caravanworld.com.au/blogs/reviews/tech-dc-dc-battery-management (checked October 2026)
CarsGuide, “Vehicles fitted with a smart alternator in Australia” – smart alternator voltage test (about 12.5 V after 5 to 10 minutes). https://carsguide.com.au/car-advice/vehicles-fitted-with-a-smart-alternator-in-australia-97156 (checked October 2026)
Anderson Power Products, SB50 connector datasheet – 50 A rating; accepts wire from 16 to 6 AWG (about 1.3 to 13.3 mm²). https://www.farnell.com/datasheets/273617.pdf (checked October 2026)
Resistivity of copper (about 1.72 × 10⁻⁸ ohm-metre at 20°C), standard physical constant used to calculate the voltage-drop example. Cable areas as published in our cable size guide.
JS Alternators, “How to test your alternator: complete guide” – resting battery and normal charging voltage ranges (as used in our alternator article). https://js-alternators.com/blogs/blog/how-to-test-alternator (checked October 2026)

26 October 2026

How do I wire a 12V relay (pins 30, 85, 86, 87)?

Quick answer

A relay uses a small current through its coil (terminals 85 and 86) to switch a large current through its contacts (terminals 30 and 87). Wire battery positive through a fuse near the battery to 30, connect 87 to the accessory and earth the accessory, then feed 86 from a fused or ignition-switched supply through your switch and connect 85 to earth. When the switch is on, the coil pulls in and 30 connects to 87; on a 5-pin changeover relay, 30 connects to 87a whenever the relay is off.

Is this a DIY job?

Difficulty: Medium
Time: 30 minutes to 2 hours, depending on the accessory and cable runs
Tools: multimeter, crimp tool, wire stripper, side cutters, spanners for the battery terminals
Skills: crimping, reading a simple wiring diagram, using a multimeter

A relay circuit is a good DIY job if you can crimp terminals well and follow a diagram. Get professional help for anything tied into the vehicle’s factory looms or body control module, and for high-current loads such as winches or inverters.

What each terminal does

These numbers come from the German DIN 72552 terminal-marking standard and are used on almost all automotive relays.

Terminal	Function	Connects to
30	Common contact	Fused battery positive (the power you’re switching)
87	Normally open contact	The load; connected to 30 only while the relay is on
87a	Normally closed contact (5-pin only)	Connected to 30 only while the relay is off
86	Coil	Switched positive from your switch
85	Coil	Earth (negative)

4-pin vs 5-pin. A 4-pin relay has 30, 85, 86 and 87: it simply turns a circuit on or off. A 5-pin relay adds 87a and is a changeover relay: the 30 contact swaps between 87a (off) and 87 (on). You can use a 5-pin relay as a 4-pin one by leaving 87a unconnected. Some 5-pin relays have two 87 terminals instead of an 87a, for feeding two outputs; check the diagram on the case.

Suppressed relays and polarity. When a relay coil switches off, it produces a voltage spike that can upset sensitive electronics. Many relays include a resistor or a diode across the coil to absorb it. A resistor-suppressed relay doesn’t care which way round 85 and 86 are wired. A diode-suppressed relay does: if you reverse it, the diode conducts straight across the coil when you switch on, the relay won’t work, and the trigger fuse or the diode can be destroyed. The negative terminal isn’t the same on every diode relay, so always follow the diagram printed on the relay.

Step by step

Switched relay circuit: battery positive through a fuse to 30, 87 to the load and earth, 86 from a fused or ignition feed through a switch, 85 to earth

Schematic only. Pin positions on the relay base vary, so match terminal numbers, not positions.

Check the load and the relay. Find the accessory’s current draw and make sure the relay’s contact rating is higher. Note that the 87a contact often has a lower rating than 87.
Size the load cable. Choose cable by copper area in mm² for the current and run length, from the battery to 30 and from 87 to the load. (see What size cable do I need for my 12V accessory?)
Disconnect the battery. Negative off first.
Mount the relay. Use a relay base with crimped terminals, mounted with the terminals facing down (or sideways) so water can’t sit in it, away from exhaust heat.
Wire 30 (power in). Run fused cable from battery positive to terminal 30. The fuse goes as close to the battery as practical and is rated at or below the cable’s rating. (see Where should the fuse go when wiring an accessory?)
Wire 87 (power out). Run cable from 87 to the accessory’s positive.
Earth the load. Connect the accessory’s negative to a clean chassis earth or straight back to the battery negative with cable of the same size.
Wire 85 (coil earth). Connect 85 to a good earth. If the relay has a diode, check which terminal the diagram shows as negative.
Wire 86 (coil trigger). Run a light cable from a fused 12V feed, through your dash switch, to 86. Use an ignition-switched feed if the accessory should only work with the key on. Fit a small fuse in this trigger circuit sized to protect its thin wire.
Check everything before power. Make sure no bare copper is showing, and that 30 and 87 haven’t been swapped with the coil terminals.
Fit the fuses and reconnect the battery. Negative on last.
Test. With the switch off, the accessory should be off. Switch on: you should hear a click and the accessory should run. If you hear a click but nothing works, check the 30 feed fuse and the load earth. If there’s no click, check the trigger fuse, the switch and the 85 earth.

Testing a relay on the bench. Measure across 85 and 86 with a multimeter on ohms: a typical coil reads tens of ohms, and an open circuit means the coil has failed (a diode relay may read differently one way round). Then apply 12V to the coil (correct polarity for a diode relay) and check with the meter that 30 and 87 now read near zero ohms.

Specs table

Example figures from one maker’s 12V automotive changeover relay

Item	Figure
Coil resistance	72 Ω ±15%
Coil current at 12 V	about 0.17 A (worked out from the coil resistance)
Contact rating, 87 (normally open)	35 A resistive
Contact rating, 87a (normally closed)	20 A resistive
Pull-in voltage	8.0 V maximum at 23°C

Relays vary widely: heavy-duty types switch much more current. Always check the rating printed on the relay you buy, and remember that motors, compressors and some lights draw more current when they start than when they’re running.

What you’ll need

12V automotive relay 4 pin or 12V automotive relay 5 pin changeover
relay base with terminals
inline blade fuse holder (two: one for the load, one for the trigger)
blade fuses
12V switch
auto cable (heavy for the load circuit, light for the trigger)
crimp terminals and adhesive lined heat shrink
relay wiring harness (a ready-made option for lights)

When to call an auto electrician

The relay will switch a high-current load such as a winch, inverter, air compressor or large light bar.
You want to trigger the relay from a factory circuit such as high beam, reverse lights or a body control module output. Some factory circuits are monitored and can throw faults.
Fuses blow, the relay clicks rapidly (chatters), or the relay or its base gets hot.
The wiring passes near airbags or SRS looms, or the vehicle is a hybrid or EV (high-voltage systems are professional-only).

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Sources

DIN 72552, “Terminal markings for motor vehicles” (Deutsches Institut für Normung) – terminal numbers 30, 85, 86, 87 and 87a. Referenced as the standard behind the numbering; not quoted.
Omron, G8JN automotive relay datasheet (via Farnell) – terminals 30, 85, 86, 87, 87a; coil resistance 72 Ω ±15%; contact ratings 35 A (NO) and 20 A (NC); pull-in voltage 8.0 V max at 23°C; versions with a suppression resistor or suppression diode. https://www.farnell.com/datasheets/103809.pdf (checked October 2026)
HELLA, “New relays” bulletin – relays are resistor- or diode-suppressed across the coil, identified from the printed schematic; on the diode type shown, 85 is negative and 86 positive. https://www.hella.com/forvia-us/assets/documents/BI_HELLA_New_Relays_EN.pdf (checked October 2026)

26 October 2026

Is it my starter motor or my battery?

Quick answer

If the dash lights go dim or out when you turn the key, or you hear rapid clicking, the battery (or its connections) is the usual cause. If the lights stay bright but you get one click or nothing, the starter motor, its solenoid or its wiring is more likely. A jump start is a good test: if the car starts straight away on a jump, look at the battery and charging system first.

Is this a DIY job?

Difficulty: Medium (the checks are easy; replacing a starter is usually Pro)
Time: 15 to 30 minutes to diagnose
Tools: digital multimeter, jumper leads or a jump pack, safety glasses, gloves, terminal brush
Skills: reading a multimeter, working safely around a battery

Most people can do these checks in the driveway. Swapping a battery is an easy DIY job. Replacing a starter motor means working under the car or deep in the engine bay, so most owners leave that to an auto electrician.

Step by step

No-start decision flowchart: battery or starter?

Make it safe. Park on level ground, handbrake on. Automatic in Park (try Neutral too). Manual in neutral with the clutch pressed fully down when you try to start.
Rule out the simple things. Check the key or remote battery, and that the immobiliser or security light isn’t flashing. A flashing key symbol points to the immobiliser, not the battery or starter.
Listen when you turn the key (or press Start). Note exactly what you hear: – Fast clicking or chattering: usually a low battery or a poor battery connection. – One solid click, then nothing: often the starter solenoid, the starter motor or the heavy cable to it. – Slow, laboured cranking: a weak battery or a high-resistance connection; sometimes a worn starter. – Nothing at all, and the dash is dead: flat battery, or a terminal that’s loose or corroded. – Grinding: the starter gear isn’t meshing properly. Stop trying and get it checked.
Do the headlight test. Switch the headlights on, then try to start. If the lights dim heavily or go out, the battery can’t supply enough current. If they stay bright and nothing happens, the power isn’t getting through the starter circuit.
Check the battery terminals. Look for white or green corrosion, loose clamps or a cracked terminal. Wiggle each clamp by hand. If one moves, that alone can stop the car starting.
Measure the battery voltage. With everything off, set the multimeter to DC volts and put the red probe on positive (+) and black on negative (−). Compare with the table below. If you’ve just driven or charged it, the reading will look better than it is. For a true reading, let it rest for several hours, ideally overnight (one battery maker suggests 24 hours without driving).
Measure while cranking. Have a helper crank the engine for a few seconds while you watch the meter. A big drop (see table) points to a weak battery. If the voltage barely moves and the starter does nothing, the problem is between the battery and the starter.
Try a jump start. Follow your owner’s manual for jump points (some cars have remote jump posts under the bonnet). If it starts normally on a jump, the battery is flat or failing. Then find out why: an old battery, a charging fault or something draining it overnight.
If a jump makes no difference, and the battery reads well, suspect the starter circuit: the starter motor, solenoid, starter relay, ignition switch, or the neutral/clutch safety switch. These need a proper circuit test.

Specs table

Symptoms and the usual cause

What happens when you turn the key	Dash lights	Most likely
Rapid clicking	Dim or flicker	Low battery or poor terminal connection
Single click, no crank	Stay bright	Starter solenoid/motor or its cable
Slow crank, then starts (or not)	Dim during crank	Weak battery, corroded cable or earth
Nothing, no dash lights	Off	Flat battery or disconnected terminal
Nothing, dash lights normal	Bright	Starter circuit, relay, ignition or safety switch, immobiliser
Grinding noise	Normal	Starter drive or flywheel ring gear

Battery voltage guide (12V lead-acid, engine off, rested)

Reading	Approximate state
About 12.6 V or more	Fully charged (battery makers often quote 12.7 to 12.8 V)
About 12.4 V or less	Partly discharged; charge it before judging
About 12.0 V or less	Flat (fully discharged) or failing

During cranking, a common workshop guide is that a healthy, charged battery shouldn’t drop much below about 9.5 V. Much lower than that suggests a weak battery or a bad connection. Lithium starting batteries and some AGM batteries read a little differently; check the battery maker’s figures.

What you’ll need

digital multimeter
jumper leads heavy duty or portable jump starter
battery terminal brush
battery terminal protector spray
smart battery charger
If confirmed: car battery or starter motor

When to call an auto electrician

The battery tests good but the car still won’t crank.
You hear grinding, or the starter keeps running after you let go of the key. If the starter won’t stop, switch off the ignition and, if it’s safe to do so, disconnect the battery negative terminal.
There’s a burning smell, smoke or a hot cable near the starter.
The car has a push-button start, keyless entry or an immobiliser warning you can’t clear.
It’s a hybrid or EV. Many hybrids don’t have a conventional starter motor, and their high-voltage systems are professional-only. Never touch orange cables.
A new battery keeps going flat. That usually means a charging fault or a drain that needs proper testing.

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Sources

RACV, “What do the car dashboard symbols and warning lights mean” – battery/charging light advice. https://www.racv.com.au/royalauto/transport/cars/what-do-the-car-dashboard-symbols-mean-and-warning-lights.html (checked October 2026)
RACV, “Car battery replacement” – battery management and registration note. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)
Century Batteries, “How to test a lead-acid battery” – 12.7 to 12.8 V fully charged; recharge at 12.5 V or below; 12.0 V fully discharged; vehicle not driven for 24 hours before testing. https://www.centurybatteries.com.au/battery-hub/expert-advice/how-to-test-a-lead-acid-battery (checked October 2026)
VARTA, “Testing the battery – step by step” – recharge a conventional battery as soon as possible if it reads below 12.4 V; a voltage reading shows state of charge, not battery health. https://www.varta-automotive.com/en/knowledge/articles/article-details/testing-the-battery—step-by-step (checked October 2026)
RACV, “Car battery guide” – 12.6 V fully charged (rested). https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
Brake & Front End, “Diagnostic solutions: testing automotive batteries and starters” – 9.5 V minimum cranking voltage threshold in a load test (workshop rule of thumb, not a formal standard); test starters only with a fully charged battery. https://www.brakeandfrontend.com/diagnostic-solutions-testing-automotive-batteries-and-starters/ (checked October 2026)

26 October 2026

How do I wire a 7-pin flat or 7-pin round trailer plug?

Quick answer

Australian 7-pin flat and 7-pin large round trailer connectors use the same pin numbers for the same jobs: 1 left indicator (yellow), 2 reversing (black), 3 earth (white), 4 right indicator (green), 5 electric brakes (blue), 6 stop lights (red) and 7 tail lights (brown). Wire each core to the terminal with the matching number moulded beside it, make sure the earth is solid, and test every function before you tow.

Is this a DIY job?

Difficulty: Medium
Time: 30 to 60 minutes for one plug
Tools: wire strippers, small screwdriver, side cutters, trailer circuit tester (or a helper), heat shrink and heat gun (optional)
Skills: stripping and terminating small wires neatly

Replacing the plug on a trailer is a reasonable DIY job. Wiring a new socket into a modern car is different: many current vehicles need a vehicle-specific towbar harness or module, and cutting into factory wiring can cause faults. That part is often best left to an auto electrician.

Plug or socket?

The socket is on the tow vehicle (at the towbar).
The plug is on the end of the trailer cable.

The pin numbers and colours are the same on both. These steps describe wiring a trailer plug; the socket is wired the same way.

Step by step

7-pin flat and 7-pin large round connector pin chart, with standard Australian colours

Identify the connector. Check whether you have a 7-pin flat, a 7-pin large round, or something else. Don’t confuse the Australian 7-pin large round with the smaller European 7-pin round: they’re wired differently and aren’t interchangeable. If you need extra circuits (battery charging, auxiliary power), a 12-pin flat connector is the usual answer.
Disconnect from the vehicle. Unplug the trailer before working on it.
Open the plug. Undo the screws and separate the body. Slide the cover and any rubber boot onto the cable before you strip it, or you won’t be able to fit them later.
Strip the outer sheath. Remove enough outer sheath to reach every terminal comfortably, without cutting into the inner cores.
Strip each core. Strip only as much insulation as the terminal needs. Twist the strands tightly. No stray strands should be able to reach a neighbouring terminal.
Match each colour to its number. Each terminal has its number moulded beside it. Use the pin chart and table below. Go by the number, not by where a terminal sits in a picture: viewed from the wire side, the layout is a mirror image of the face.
Fasten each core. Insert the twisted strands fully under the terminal screw or into the crimp and tighten firmly. Tug each wire gently to check it’s held.
Check the earth. Pin 3 (white) is the earth. On the trailer, run the earth wire to a clean, bare-metal point on the chassis with a ring terminal. Don’t rely on the coupling or towball to carry the earth. A poor earth is the most common cause of dim, flickering or “crossed” trailer lights.
Fit the cable clamp. Tighten the strain-relief clamp on the outer sheath, not on the inner cores, so a pull on the cable doesn’t load the terminals.
Close the plug. Make sure no wire is pinched, and fit any seals.
Test every function. Plug into the vehicle or a trailer circuit tester and check: tail lights, left indicator, right indicator, stop lights, reversing lights (if fitted) and electric brakes (if fitted, using the brake controller’s manual output). Check hazard lights work too.
Protect it. Use the plug cover or a holder when the trailer is unhooked, so water and dust stay out of the pins.

Specs table

Australian 7-pin flat and 7-pin large round (AS 4177.5)

Pin	Function	Cable colour
1	Left-hand indicator	Yellow
2	Reversing lights	Black
3	Earth (return)	White
4	Right-hand indicator	Green
5	Electric brakes	Blue
6	Stop lights	Red
7	Tail, clearance and side marker lights	Brown

Notes on these pins

Pin 2 is for reversing lights. Don’t use it for auxiliary power, a breakaway feed or a pump, even if the trailer has no reversing lights. If you need those circuits, use a 12-pin connector.
Pin 5 is for electric brakes only. If the trailer has no electric brakes, leave it unused.
Pin 3 carries the return current for everything else, including the brakes. A good earth matters.
Colours on older trailers, or on cable made to another code, may differ. Always confirm with a tester before relying on colours.

12-pin flat (for comparison)

Pins 1 to 7 on a 12-pin flat connector follow the same functions and colours as above. Pins 8 to 12 add circuits such as battery charging or auxiliary power, a second earth, rear fog lights and a spare. See (see What’s the difference between 7-pin flat, 7-pin round and 12-pin trailer plugs?).

Trailer brakes (check your state rules)

Braking requirements depend on the trailer’s mass. Under the national guide for small trailers (VSB 1), a single-axle trailer up to 750 kg gross trailer mass (GTM) doesn’t need brakes. Above that, brakes are required. Over-run (mechanical) brakes are only allowed up to 2000 kg GTM. Over 2000 kg GTM, the trailer needs brakes on all wheels, operable from the driver’s seat, that apply automatically and stay on for at least 15 minutes if the trailer breaks away. In practice that means electric brakes, a brake controller and a breakaway system. Check the rules for your trailer with your state road authority.

What you’ll need

7 pin flat trailer plug or 7 pin large round trailer plug
7 core trailer cable (if replacing the cable)
trailer plug cover or trailer plug holder
trailer circuit tester
ring terminals and adhesive heat shrink
wire strippers
towbar wiring harness (vehicle-specific, if fitting a new socket to a modern car)

When to call an auto electrician

You’re adding a trailer socket to a modern car. Many vehicles use CAN-bus or LED lighting that needs a plug-in harness or isolation module; tapping into tail-light wiring can trigger faults.
You’re fitting an electric brake controller, breakaway system or 12-pin auxiliary/charging circuit. These carry high current and are safety-critical.
The lights still don’t work properly after re-wiring, or blow fuses.
The trailer wiring itself is damaged, corroded or has been repaired many times.

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Sources

Standards Australia, AS 4177.5 – Caravan and light trailer towing components, Part 5: Electrical connectors (the standard itself is paywalled; pin functions confirmed through the secondary sources below). Reference via Australian Business Licence and Information Service: https://ablis.business.gov.au/VIC/pages/ce32f8e1-d088-45fc-8849-115e51df44ee.aspx (checked October 2026)
ExplorOz, “Trailer wiring diagrams” – pin functions and colours for 7-pin flat, 7-pin large round and 12-pin flat. https://www.exploroz.com/vehicle/electrics/trailerwiringdiagrams.aspx (checked October 2026)
Wikipedia, “Trailer connectors in Australia” – pin 2 and pin 5 cautions, viewing-direction notes, ISO 1724 differences (cites VSB 1 section 14). https://en.wikipedia.org/wiki/Trailer_connectors_in_Australia (checked October 2026)
RACQ, “A guide to trailer brakes” – plain-English summary of brake, breakaway and controller requirements by trailer mass. https://www.racq.com.au/articles/driving-tips/a-guide-to-trailer-brakes (checked October 2026)
Department of Infrastructure, Transport, Regional Development, Communications and the Arts, Vehicle Standards Bulletin 1 (VSB 1) Revision 5 – Trailers with an aggregate trailer mass of 4.5 tonnes or less (June 2009) – connectors must comply with AS 2513 or AS 4177.5 (up to 3.5 t ATM); pin 5 for service brakes only; brake requirements by GTM. https://www.infrastructure.gov.au/sites/default/files/documents/vehicle-standards-bulletin-1-revision5-trailers-with-an-aggregate-trailer-mass-of-4-5-tonnes-or-less-june2009-pdf.pdf (checked October 2026)

26 October 2026

What should I do when a warning light or fault code comes up on my dashboard?

Quick answer

Check the colour first. A red light means a serious problem: stop somewhere safe as soon as you can and check your owner’s manual before driving on. An amber or orange light means a fault that needs checking soon, and a flashing light is more urgent than a steady one. Green and blue lights just show that something is switched on.

Is this a DIY job?

Difficulty: Easy to check and read codes; the repair depends on the fault
Time: 5 to 15 minutes to check and read codes
Tools: owner’s manual, OBD2 code reader (optional), torch
Skills: none for the checks; basic confidence plugging in a code reader

Anyone can do the first checks and read a basic engine fault code. Working out what’s actually wrong, and fixing it, often needs proper diagnostic equipment.

Step by step

Dashboard warning light colour key: red, amber, green and blue

Note exactly what you see. The colour, the symbol, whether it’s steady or flashing, any message on the screen, and whether other lights came on at the same time. Note how the car is driving: any loss of power, noise, smell or steam. A photo of the dash helps the person who diagnoses it.
If it’s red, stop safely. Pull over when it’s safe, switch on your hazard lights and look up the symbol in the owner’s manual. – Oil pressure light: switch the engine off straight away. Driving on with no oil pressure can wreck the engine quickly. Check the oil level once the car has been off for a few minutes, on level ground. – Engine temperature light: stop and switch off. Don’t open the radiator or coolant cap while the engine is hot: it can spray scalding coolant. – Brake warning light: check the handbrake (or electronic park brake) is fully off. If the light stays on, the brake fluid may be low or there may be a fault in the braking system. Have the brakes checked straight away, even if they feel normal. Don’t drive if the pedal feels soft or goes further than normal. – Battery or charging light: the alternator isn’t charging. The car may run for a while on the battery, but it can stop without much warning. If the temperature is also rising, the belt may have broken: stop. (see How do I know if my alternator needs replacing?)
If it’s amber, get it checked soon. You can usually drive carefully to a workshop or home, but don’t ignore it. Avoid long trips or towing until it’s been looked at.
If the engine light is flashing, ease off. A flashing engine or “check engine” light usually means a serious misfire. Unburnt fuel can overheat and damage the catalytic converter. Reduce speed, avoid heavy loads and get it checked promptly. If the car is shaking badly or losing power, stop.
Check the simple things. Some amber lights have simple causes: a tyre pressure light may just need the tyres pumped up to the placard pressures, and on some cars a loose fuel cap can set an engine fault. Check fluid levels if you know how.
Read the fault code (optional). Most modern cars have an OBD2 diagnostic port, usually under the dash on the driver’s side. Plug in a code reader with the ignition on and write down every code. Codes starting with “P” relate to the powertrain (engine and transmission).
Don’t just clear the code. Clearing a code turns the light off but doesn’t fix anything, and it erases information a technician can use. If the fault is still there, the light will come back.
Book it in. Give the technician your notes, photos and any codes. A code points to the system that has a problem, not always to the exact part, so expect them to test before replacing anything.

Specs table

Common warning lights

Symbols and colours vary between makes. Your owner’s manual has the definitive list for your car.

Warning light	Usual colour	What it usually means	What to do
Oil pressure (oil can)	Red	Low oil pressure	Stop and switch off now
Engine temperature (thermometer)	Red	Engine overheating	Stop, switch off, let it cool
Brake system (“BRAKE” or circle with “!”)	Red	Park brake on, low fluid or brake fault	Check park brake; if it stays on, get the brakes checked straight away. Don’t drive if braking feels wrong
Battery / charging	Red	Charging system not charging	Head for help; stop if temperature rises
Airbag / SRS	Red or amber	Fault in the airbag system	Get it checked; airbags may not work. Professional-only
Check engine / engine management	Amber	Engine or emissions fault	Steady: book in soon. Flashing: ease off and get it checked promptly
ABS	Amber	Anti-lock braking not working	Normal brakes usually still work; book in soon
Tyre pressure (TPMS)	Amber	One or more tyres low	Check and inflate to placard pressures
Power steering (steering wheel)	Amber or red	Power steering fault	Steering may be heavy; drive carefully to help
Diesel particulate filter (DPF)	Amber	Filter needs to clean itself (regenerate)	Follow the manual; often a longer run at steady speed
Glow plug / pre-heat (coil)	Amber	Diesel pre-heat. If it flashes while driving, often an engine fault	Check the manual; book in if it flashes

Fault code letters

First letter	System
P	Powertrain (engine, transmission)
B	Body (airbags, central locking, comfort systems)
C	Chassis (ABS, steering, suspension)
U	Network (communication between modules)

Basic code readers usually show P codes only. B, C and U codes often need a more capable scan tool.

What you’ll need

OBD2 code reader or Bluetooth OBD2 adaptor
tyre pressure gauge
If the battery or charging light is on: digital multimeter

When to call an auto electrician

Any red warning light that stays on after the simple checks.
The engine light is flashing, or comes back after clearing.
Airbag/SRS warnings. Airbag systems are professional-only: a fault can stop airbags working, and incorrect handling can set one off.
ABS, stability control, power steering or electronic park brake warnings.
Several unrelated lights come on at once. That can point to a charging, earth or network fault.
Any “hybrid system” or high-voltage warning on a hybrid or EV. Don’t attempt any work on high-voltage parts or orange cables.

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Sources

RACV, “What do the car dashboard symbols and warning lights mean” – colour meanings; red or flashing lights often mean stop; oil pressure and temperature: pull over and switch off; brake light that stays on needs checking immediately; charging light points to the charging system; flashing check engine light needs immediate attention; persistent DPF warnings need servicing. https://www.racv.com.au/royalauto/transport/cars/what-do-the-car-dashboard-symbols-mean-and-warning-lights.html (checked October 2026)
NRMA, “What do my dashboard warning lights mean” – red and orange lights; don’t just reset the light, have a technician diagnose and clear the code. https://mynrma.com.au/cars-and-driving/car-servicing/resources/what-do-my-dashboard-warning-lights-mean (checked October 2026)
SAE J2012 – Diagnostic trouble code definitions (P, B, C, U code structure). Referenced as the industry standard; not quoted.

26 October 2026

How do I charge a car battery with a battery charger?

Quick answer

Use a smart (multi-stage) charger set to the mode that matches your battery: standard for flooded and EFB batteries, AGM for AGM, and lithium only for a lithium battery. With the charger unplugged, connect the red clamp to the battery’s positive post and the black clamp to a bare-metal earth point on the chassis or engine (or the point your owner’s manual specifies), using the negative post only if there’s no suitable earth point. Then plug in and switch on. Charge in a well-ventilated place away from sparks and flames, because charging gives off hydrogen. Never charge a battery that is frozen, swollen, cracked or leaking. When it’s finished, switch off and unplug first, then remove black and then red.

Is this a DIY job?

Difficulty: Easy
Time: 10 minutes to set up; charging takes from a couple of hours to a day depending on the charger and how flat the battery is
Tools: smart battery charger, safety glasses, gloves, spanner (only if removing the battery)
Skills: following the charger’s instructions and keeping positive and negative straight

Charging a 12V car battery is a safe job if you use a smart charger and follow the basics. Get help if the battery is damaged, if your car’s manual says the battery must only be charged at a workshop, or if it’s a hybrid or EV and you’re unsure which battery you’re dealing with.

Choose the right charger and mode

Smart (multi-stage) chargers check the battery, adjust the current as it fills and then drop to a maintenance (float) mode. Most can be left connected safely. NRMA and RAC WA both point people towards this type.
Simple trickle chargers have no electronics to check the battery and usually no overcharge protection. You have to watch them and switch them off yourself.
Match the mode to the battery. Look at the battery label for “AGM”, “EFB” or “lithium”. EFB (enhanced flooded battery) is a tougher version of the standard flooded battery, built to cope with the constant restarts in stop-start vehicles. Flooded, EFB and AGM are all lead-acid batteries, and many chargers handle them on one setting: one Australian battery maker’s charger, for example, uses a single AGM/flooded/EFB setting. Others have separate AGM or “start-stop” modes, so check the charger manual and pick the setting it lists for your battery type.
Lithium batteries need a lithium mode. Chargers built for lead-acid batteries can damage a lithium battery. Equally, don’t use a lithium setting on a lead-acid battery unless the charger’s manual says it’s suitable. Only use a charger the battery maker approves.
Size the charger to the battery. A common guide is a charge current of about one tenth of the battery’s amp-hour (Ah) rating, for example about 6 A for a 60 Ah battery. Smart chargers set this themselves.
Avoid “recovery” or high-voltage modes on a battery that’s still in the car. Some chargers have a reconditioning mode that goes above normal charging voltage. Battery makers advise disconnecting or removing the battery before using anything above 14.8 V.

Step by step

Check the battery first. Safety glasses and gloves on. If the case is swollen, bulging, cracked or leaking, or it smells of rotten eggs, don’t charge it.
Never charge a frozen battery. In alpine areas, a battery that has frozen can explode when charged. Let it thaw and have it checked.
Pick a ventilated spot. Charging lead-acid batteries gives off hydrogen, which is explosive. Work outdoors or in an open garage, away from flames, cigarettes, grinders and anything that sparks. Keep vent caps or vent holes clear.
Check your owner’s manual. Many modern cars say exactly where to connect a charger, and some have remote jump-start points in the engine bay. Note any warnings about battery sensors, stop-start or battery location (some are under a seat or in the boot).
Switch the car off. Ignition off, key out, and lights, radio and other accessories off.
Decide: in the car or out. With a smart charger you can usually charge the battery in the car. If you need to remove it, disconnect the negative (−) terminal first, then the positive (+), and lift the battery out upright. (see How do I replace a car battery?)
Make sure the charger is unplugged and switched off at the wall.
Connect the red clamp to the positive (+) post.
Connect the black clamp. If the battery is out of the car, connect it to the negative (−) post. If it’s in the car, follow the owner’s manual. Charger makers’ instructions generally say to use a bare, unpainted metal earth point on the body or engine, away from the battery and fuel lines, and to use the negative post only if there’s no suitable earth point. On cars with a battery sensor on the negative terminal, the earth point matters more: the charge has to pass through the sensor so the car’s battery management system can see it.
Select the battery type (standard, AGM, lithium) and the charge rate if the charger asks.
Plug in and switch on. Check the charger shows it has started and the polarity is right.
Check on it now and then. If the battery gets hot (NRMA gives about 50°C as the point to stop), bubbles violently or smells, switch off at the wall and stop.
Wait for the “full” or maintenance light. A smart charger moves to float mode when it’s done. Battery makers suggest not leaving a battery on a charger for more than 24 hours unless the charger is designed to maintain it.
Switch off and unplug the charger at the wall.
Remove the black clamp first, then the red.
Refit the battery if you removed it. Hold it down firmly, then connect the positive (+) first and the negative (−) last. Reset the clock, radio and windows if needed.
Test after it has rested. For a true reading, let the battery sit for several hours (overnight is best) and measure the voltage. About 12.6 V means fully charged. If it won’t hold charge, have it tested. (see How do I test my car battery?)

How long does it take?

It depends on how flat the battery is, its size and the charger’s current. RACV says charging at home can take anywhere from 2 to 24 hours depending on the charger. NRMA says a trickle charger can take from a few hours to more than a day on a flat battery. A rough estimate is the amp-hours you need to put back divided by the charger’s amps, plus extra time for the final stages, when a smart charger slows down.

Driving is not a good substitute for a charger. RAC WA notes that recharging a flat battery fully by driving can take up to eight hours of continuous driving, and NRMA warns that jump-starting and driving won’t fully recharge a completely flat battery.

Specs table

Item	Figure	Note
Charge current guide	About 10% of the battery’s Ah rating	e.g. about 6 A for a 60 Ah battery
Maximum charging voltage, flooded/EFB/AGM car battery (at 25°C)	14.8 V	Battery maker technical guidance; higher “recovery” modes need the battery disconnected
Stop charging if the battery gets hot	About 50°C (NRMA); acid above 55°C (battery maker guidance)	Switch off and let it cool
Below 0°C	Battery accepts very little charge	Never charge a frozen battery
Maximum time on a non-maintaining charger	24 hours	Battery maker guidance
Fully charged, rested	About 12.6 V	RACV, standard lead-acid battery
Lithium batteries	Lithium mode only	Use the battery maker’s charging specs

Charging voltages vary with temperature and battery design, so a smart charger with temperature compensation and the right battery mode does this for you.

What you’ll need

smart battery charger (multi-stage, with modes for your battery type)
lithium battery charger (only if you have a lithium battery)
battery maintainer (for cars that sit for long periods)
battery terminal brush
safety glasses and nitrile gloves

When to call an auto electrician

The battery is swollen, cracked, leaking, frozen or smells of rotten eggs.
It won’t take a charge, or it goes flat again within days. There may be a drain or charging fault. (see Why does my car battery keep going flat?)
Your manual says the battery must be charged or replaced by a dealer or workshop, or the battery needs registering after replacement.
The car is a hybrid or EV. The 12V battery can usually be charged, but the high-voltage battery and orange cables are professional-only.
You’re not sure which charger mode suits your battery.

Need an auto electrician? Find local auto electricians and mobile services in your city.

Find an auto electrician near you

Sources

NRMA, “Car maintenance: charging your car battery” – smart vs simple trickle chargers; a few hours to more than a day; connect before switching on and switch off before disconnecting; flammable gases; never charge a frozen battery; stop if around 50°C. https://www.mynrma.com.au/open-road/advice-and-how-to/car-maintenance/charging-your-car-battery (checked October 2026)
RAC WA, “Can flat car batteries be charged?” – hydrogen and oxygen gases need ventilation; don’t charge a cracked battery; smart multi-stage chargers; up to eight hours of continuous driving to fully recharge. https://rac.com.au/horizons/drive/recharge-flat-battery (checked October 2026)
NRMA, “Common car battery myths” – jump-starting and driving won’t fully recharge a completely flat battery. https://www.mynrma.com.au/open-road/advice-and-how-to/car-maintenance/car-battery-myths (checked October 2026)
RACV, “Car battery replacement” – home charging 2 to 24 hours depending on the charger; battery registration on some vehicles. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)
RACV, “Car battery guide” – 12.6 V fully charged (rested). https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
Banner Batteries, “How to: correctly charging the AGM, EFB and SLI car battery” – 14.8 V maximum charging voltage at 25°C; stop if acid exceeds 55°C; little charge accepted below 0°C; charge current about one tenth of capacity; disconnect before modes above 14.8 V; ventilation. https://www.bannerbatterien.com/en/Battery-knowledge/1-HOW-TO-Correctly-charging-the-AGM-EFB-SLI-car-battery (checked October 2026)
Banner Batteries, “Battery sensor – application and function” – sensor at the negative terminal; charging current must pass through the sensor; black clamp to bare-metal earth. https://www.bannerbatterien.com/en/Battery-knowledge/20-Battery-sensor-%E2%80%93-application-and-function (checked October 2026)
VARTA, “How to charge car batteries at home” – ventilation in enclosed spaces (explosive hydrogen); charger mode depends on battery type; no more than 24 hours on the charger. https://www.varta-automotive.com/knowledge/articles/article-details/charging-car-batteries (checked October 2026)
Century Batteries, “How to charge a lead-acid car battery” – charge rate about 10% of Ah; connection and disconnection order; check for bulging or damage first (official guide; see for model-specific steps). https://www.centurybatteries.com.au/battery-hub/expert-advice/how-to-charge-a-lead-acid-car-battery (checked October 2026)
Century Batteries, “How to maintain your lithium deep cycle battery” – use a charger with a dedicated lithium mode; lead-acid chargers can damage lithium batteries. https://www.centurybatteries.com.au/battery-hub/expert-advice/how-to-maintain-your-lithium-deep-cycle-battery (checked October 2026)
CTEK, “Charging an AGM battery: settings, safety and best practice” – incorrect charging profile can undercharge or overcharge an AGM battery (official guide). https://ctek.com/en-us/blogs/ctek-magazine/charging-an-agm-battery-settings-safety-and-best-practice (checked October 2026)
Century Batteries, CC1212-XLi battery charger owner’s manual – single charge setting for AGM, flooded and EFB batteries (14.4 V absorption, 13.6 V float). Also: on negatively earthed vehicles, red clamp to battery positive first, then black clamp to the vehicle’s chassis, away from fuel lines. https://www.centurybatteries.com.au/media/tapbtybn/cc1212-xli_century_owners_manual_0123_r12.pdf (checked October 2026)
CTEK, “How to connect a car battery charger” and Australian FAQ – connect the black clamp to unpainted metal on the chassis away from the battery, negative post only as a fallback; on vehicles with a battery management system, connect to the earth point rather than the negative post. https://www.ctek.com/au/faq (checked October 2026)

26 October 2026

What’s the difference between flooded, EFB, AGM and lithium car batteries?

Quick answer

A flooded battery is the standard lead-acid type with liquid acid, and it suits most cars without stop-start. An EFB (enhanced flooded battery) is a tougher flooded battery made for entry-level stop-start cars. An AGM (absorbent glass mat) battery holds its acid in glass-fibre mats, is sealed, and is used in cars with more advanced stop-start and braking energy recovery. Lithium batteries are a different chemistry used in some newer electric vehicles and as specialist replacements, and they need a charging system designed for them. Always replace like with like or upgrade: never fit a flooded battery to a car that came with EFB or AGM.

Is this a DIY job?

Difficulty: Easy (choosing the battery)
Time: 10 minutes to identify your battery type
Tools: torch, owner’s manual
Skills: reading a battery label

Working out which type you have is easy. Fitting it may not be: many modern cars need the new battery registered or coded to the car’s computer, and some batteries sit under seats or in the boot. (see How do I replace a car battery?)

The four types at a glance

Flooded (conventional lead-acid)

The traditional car battery. The lead plates sit in liquid sulphuric acid. RACV describes it as the most affordable and widely available type for petrol and diesel cars, but heavier and less durable in extreme heat or cold.

Most modern flooded batteries are calcium types, sold as “maintenance free”. RAC WA explains that calcium in the plates cuts gassing, water loss and self-discharge compared with older antimony batteries, which need topping up.
Built for short, high-current bursts to start the engine, not for being run flat over and over.
Not suitable for stop-start cars.

EFB (enhanced flooded battery)

Still a wet (flooded) battery, but built to handle more charge and discharge cycles and to recharge faster.

RAC WA and NRMA both describe EFB as the battery for entry-level stop-start systems.
Battery makers describe it for compact and mid-size cars with simple stop-start, usually without braking energy recovery.
If your car came with an EFB, replace it with an EFB. An AGM can also be used, but check with the battery maker first.

AGM (absorbent glass mat)

A lead-acid battery with the acid soaked into glass-fibre mats instead of sloshing freely. It’s sealed and leak-proof, and it recombines most of its gas internally, so it doesn’t lose water and must never be opened.

Used in cars with advanced stop-start and braking energy recovery (often larger cars, SUVs and premium models), where the battery is cycled hard and partly charged much of the time.
RACV says AGM batteries generally last five to seven years, but possibly less with stop-start use, compared with three to five years for standard lead-acid.
Costs more than flooded or EFB.
Needs a charger with an AGM mode. (see How do I charge a car battery with a battery charger?)
If your car came with an AGM, replace it with an AGM. Battery makers say only an AGM may be used.

Lithium

Lithium batteries use a completely different chemistry from lead-acid.

Some newer electric vehicles now come with a lithium-ion low-voltage battery in place of the old 12V lead-acid battery. These can run at a different nominal voltage (for example 14.4 V or 16 V) and are replaced to the maker’s specification only.
Aftermarket lithium starting batteries exist, but they are not a straight swap for lead-acid in most cars. The car’s charging system, battery sensor and battery management software are set up for the battery type it was built with.
Lithium batteries need a lithium charger or lithium mode. A lead-acid charger can damage them.
In 4WDs and caravans, lithium is mainly used as a deep-cycle auxiliary battery, not a starting battery. That’s a separate topic.

Why stop-start cars need EFB or AGM

A stop-start car switches the engine off at the lights and restarts it many times on every trip. The battery also powers the lights, fan, screens and audio while the engine is off. A conventional battery isn’t built for this constant cycling.

One battery maker says a conventional battery fitted to a stop-start car that came with AGM or EFB fails within a few months, even if you switch stop-start off.
Another warns that replacing an AGM or EFB with a normal battery leads to rapid deterioration, and that a wrong battery can cause stop-start faults and loss of comfort functions.
Cars with braking energy recovery run the battery partly charged so it can soak up energy when you slow down. AGM handles this better than EFB.

Upgrading and downgrading

Car came with	Replace with	Don’t fit
Flooded	Flooded, EFB or AGM (check size, terminals and CCA)	—
EFB	EFB or AGM	Flooded
AGM	AGM only	EFB or flooded
Lithium (EV low-voltage battery)	The maker’s specified battery	Lead-acid, unless the maker allows it

EFB and AGM batteries are built for different jobs, so the safest choice is the same type the car came with. Battery makers and an Australian battery distributor say an AGM can replace an EFB, but an EFB should never replace an AGM. If you do change type, check with the battery maker first. At least one Australian battery maker says its AGM batteries suit under-bonnet fitting only where the car came with an AGM. And on some cars the battery type must also be coded into the car’s computer so it charges the new battery correctly.

Battery registration and coding

Many modern cars have a battery management system with a sensor on the negative terminal. It tracks charge, temperature and battery health, and adjusts charging to suit. RACV notes that some vehicles with a battery management system need a new battery registered. If you skip it, the car can keep charging the new battery as if it were the worn-out old one, and stop-start or comfort features may misbehave.

If you replace the battery yourself, disconnect the negative terminal first and reconnect it last, and find out beforehand whether your car needs registration. A workshop or battery outlet with the right scan tool can do this.

Specs table

	Flooded	EFB	AGM	Lithium
Electrolyte	Liquid acid	Liquid acid	Acid held in glass mat	No acid (lithium chemistry)
Sealed, no top-up	Calcium types: low or no maintenance	Low or no maintenance	Yes; never open	Yes
Stop-start	No	Entry-level systems	Advanced systems, braking energy recovery	Only where fitted by the maker
Typical life (RACV)	About 3–5 years	Not stated	About 5–7 years, possibly less with stop-start	Not stated
Charger mode	Standard	Standard (check charger manual)	AGM	Lithium only
Maximum charging voltage (battery maker guidance, at 25°C)	14.8 V	14.8 V	14.8 V	Battery maker’s spec

Battery life depends heavily on driving habits, heat and how often the car is used. Check the label and owner’s manual for your car’s exact battery.

Battery ratings you’ll see on the label

Rating	What it means
CCA (cold cranking amps)	Amps the battery can deliver for 30 seconds at −18°C while staying at or above 7.2 V. Replace with the same or higher CCA (RACV).
RC (reserve capacity)	How long the battery can supply a steady load. NRMA calls it a good indicator for Australia’s warmer climate.
Ah (amp-hours)	Capacity, mainly used on European-sized batteries.
Group size	The physical size and terminal layout. RACV suggests matching the group size code from the old battery if you don’t have the manual.

What you’ll need

EFB car battery (for entry-level stop-start)
AGM car battery (for advanced stop-start)
conventional car battery (for cars without stop-start)
smart battery charger (with AGM mode)
battery terminal protector spray

When to call an auto electrician

Your car has stop-start or a battery sensor and you’re not sure which type it needs.
The car needs the new battery registered or coded.
The battery is under a seat, in the boot or behind trim with vent tubes that must be refitted.
You want to fit a lithium starting battery or a second battery.
The car is a hybrid or EV. Their high-voltage batteries and orange cables are professional-only.

Need an auto electrician? Find local auto electricians and mobile services in your city.

Find an auto electrician near you

Sources

RAC WA, “Car batteries explained” – AGM construction; EFB as entry-level stop-start battery; calcium vs antimony; replace EFB with EFB and AGM with AGM. https://rac.com.au/horizons/drive/car-batteries-explained (checked October 2026)
RACV, “Car battery guide: how they work, when to replace them, and how to jump-start” – flooded vs AGM; lifespans (three to five years lead-acid, five to seven years AGM, possibly less with stop-start); hybrids pair a lead-acid 12V battery with a lithium-ion or NiMH traction battery; same or higher CCA; group size. https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
RACV, “Car battery replacement” – some vehicles with battery management systems require new batteries to be registered. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)
NRMA, “Stop-start batteries” – EFB meets entry-level stop-start requirements; AGM for stop-start. https://mynrma.com.au/roadside-assistance/car-batteries/stop-start (checked October 2026)
NRMA, “Common car battery myths” – CCA definition; reserve capacity as an indicator for Australian conditions. https://www.mynrma.com.au/open-road/advice-and-how-to/car-maintenance/car-battery-myths (checked October 2026)
RAC WA, “Can flat car batteries be charged?” – conventional starting batteries aren’t designed to be run almost completely flat. https://rac.com.au/horizons/drive/recharge-flat-battery (checked October 2026)
VARTA, “Do you need EFB or AGM battery?” – which vehicles suit EFB and AGM; only AGM may replace AGM; EFB to AGM upgrade; battery sensor and BMS. https://www.varta-automotive.com/knowledge/articles/article-details/efb-and-agm-differences (checked October 2026)
VARTA, “Start-stop battery replacement” – replace with the same type; normal battery in place of AGM/EFB deteriorates rapidly; AGM better suited to braking energy recovery. https://www.varta-automotive.com/en/knowledge/articles/article-details/start-stop-battery-replacement (checked October 2026)
Banner Batteries, “What is an AGM battery?” – glass mat construction; valve-regulated recombination battery; no water loss; don’t open; replace AGM only with AGM. https://www.bannerbatterien.com/en/Battery-knowledge/64-What-is-an-AGM-battery (checked October 2026)
Banner Batteries, “Battery sensor – application and function” – sensor on the negative terminal; conventional battery in a start-stop car that uses AGM/EFB fails within a few months. https://www.bannerbatterien.com/en/Battery-knowledge/20-Battery-sensor-%E2%80%93-application-and-function (checked October 2026)
Banner Batteries, “How to: correctly charging the AGM, EFB and SLI car battery” – maximum charging voltage 14.8 V at 25°C for AGM, EFB and conventional batteries. https://www.bannerbatterien.com/en/Battery-knowledge/1-HOW-TO-Correctly-charging-the-AGM-EFB-SLI-car-battery (checked October 2026)
Battery University, “BU-902a: How to measure CCA” – SAE J537 CCA definition (−18°C, 30 seconds, 7.2 V). https://www.batteryuniversity.com/article/bu-902a-how-to-measure-cca/ (checked October 2026)
Tesla, “Model Y service manual – electrical technical data” – later models list a lithium-ion low-voltage battery (14.4 V or 16 V nominal) in place of the earlier 12V flooded lead-acid battery. https://service.tesla.com/docs/ModelY/ServiceManual/en-us/GUID-8CBDB47F-0D3A-4827-AB98-982A92234D79.html (checked October 2026)
Century Batteries, “How to maintain your lithium deep cycle battery” – lithium batteries need a lithium-mode charger; lead-acid chargers can damage them. https://www.centurybatteries.com.au/battery-hub/expert-advice/how-to-maintain-your-lithium-deep-cycle-battery (checked October 2026)
R & J Batteries, ISS (stop-start) battery bulletin – EFB batteries can be replaced with AGM; AGM should not be replaced with EFB. https://www.rjbatt.com.au/media/ov0bq0bh/iss_bulletin.pdf (checked October 2026)
Century Batteries, “ISS, hybrid and car batteries” category brochure (2026) – ISS AGM batteries suit under-bonnet fitment only when the original battery is an AGM. https://www.centurybatteries.com.au/media/rfojhl1b/cb103-3470d-century-2026-au-iss-hybrid-and-car-pv-batteries-category-brochure-20pp-a4-lr.pdf (checked October 2026)

26 October 2026

Author: admin

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