Category: DIY how-to

Quick answer

Pick a terminal sized for your cable’s copper area in mm² (not its “mm” label), strip just enough insulation to fill the terminal barrel, and crimp it with a ratchet crimper using the die that matches the terminal. A good crimp passes a hard tug test without the wire moving. Finish with adhesive-lined heat shrink wherever the joint will see water, dust or vibration.

Is this a DIY job?

• Difficulty: Easy
• Time: 2 to 5 minutes per terminal once you’re set up
• Tools: ratchet crimper with the right dies, wire stripper, side cutters, heat gun
• Skills: none beyond care and patience; practise on offcuts first

Crimping is one of the most useful skills for any 12V job, and a good tool does most of the work. Leave it to a professional if the terminals are part of a factory loom connector, an airbag circuit, or anything high-current like starter or winch cables.

Step by step

1. Make it safe. If the wire is connected to anything live, pull the circuit’s fuse or disconnect the battery first: negative off first, and negative back on last when you’re done.
2. Check the cable size in mm². Read the printing on the cable, or check the reel. Australian auto cable sold as “3mm” has about 1.13 mm² of copper, “4mm” about 1.84 mm² and “6mm” about 4.59 mm². (see What size cable do I need for my 12V accessory?)
3. Choose a terminal that suits that copper area. Insulated terminals are colour-coded by wire range (see the table below). For a sealed, tidy job, choose terminals with a nylon sleeve or plan to use heat shrink. Use stranded auto cable; solid-core wire isn’t suited to crimp terminals.
4. Slide on the heat shrink first. It’s easy to forget, and once the terminal is on you can’t add it.
5. Strip the insulation. Remove only enough to fill the metal barrel of the terminal. Use a stripper set to the right size so you don’t cut or nick strands. Twist the strands lightly so none stray.
6. Insert the wire. Push the bare copper fully into the barrel. On an insulated terminal, the end of the insulation should sit just inside the plastic sleeve. On an open-barrel (non-insulated) terminal, the copper sits under the larger front tabs and the insulation sits under the smaller rear tabs, with a few strand ends just visible past the front tabs.
7. Use the matching die. Put the terminal in the die that matches its colour or size. Insulated terminals and open-barrel terminals need different dies; one die won’t do both properly.
8. Crimp in one full stroke. Squeeze the ratchet crimper until it releases by itself. The ratchet stops you letting go half way, which is the most common cause of loose crimps.
9. Tug test it. Hold the terminal and pull the wire firmly. It must not slide, rotate or pull out. If it moves, cut it off and start again; don’t re-crimp the same terminal.
10. Inspect it. You shouldn’t see loose strands outside the barrel, insulation trapped under the copper crimp, or a cracked sleeve.
11. Seal it. Slide the adhesive-lined heat shrink over the barrel and onto the cable insulation, then heat it evenly until it shrinks and a little adhesive shows at each end.
12. Restore power and test. Refit the fuse or reconnect the battery (negative last) and check the circuit works.

Specs table

Insulated terminal colours and Australian auto cable

The colour code on insulated crimp terminals is widely used across makers. Always check the wire range printed on the packet.

Terminal colour	Wire range	Australian auto cable that fits
Red	0.5 to 1.5 mm²	3mm auto cable (1.13 mm²)
Blue	1.5 to 2.5 mm²	4mm auto cable (1.84 mm²)
Yellow	4 to 6 mm²	5mm (2.90 mm²) and 6mm (4.59 mm²) auto cable

Note: 5mm auto cable (2.90 mm²) is too big for blue terminals, so auto electricians use yellow. It sits at the small end of the yellow range, so use a good ratchet crimper on the yellow die and always pull-test the crimp firmly. Some terminal makers print a wider yellow range, so check the packet.

Heavier cable (8 B&S and up) uses tubular copper lugs crimped with a hex or hydraulic lug crimper, not these terminals.

How strong is a good crimp?

For reference, the UL 486A standard sets minimum pull-out forces for crimped terminals. A good crimp should comfortably beat a firm hand tug.

Wire size	Approx. copper area	UL 486A minimum pull-out
18 AWG	0.82 mm²	89 N (about 9 kg)
16 AWG	1.31 mm²	133 N (about 13.6 kg)
14 AWG	2.08 mm²	222 N (about 22.7 kg)
12 AWG	3.31 mm²	311 N (about 31.8 kg)

These figures are a guide to how much a sound crimp should hold. A home tug test can’t measure them, but a crimp that pulls out by hand is well short.

What you’ll need

• ratchet crimper insulated terminals
• ratchet crimper non-insulated terminals (if you use open-barrel terminals)
• automatic wire stripper
• insulated crimp terminal kit
• heat shrink crimp terminals (for wet or exposed locations)
• adhesive lined heat shrink
• heat gun
• auto cable (sized for the job)

When to call an auto electrician

• The terminals are inside a factory connector plug. These need the correct pin, seal and often a dedicated crimp tool.
• The wiring is near airbags, seatbelt pretensioners or their yellow looms. Airbag (SRS) wiring is professional-only.
• The vehicle is a hybrid or electric vehicle and the cable is orange. High-voltage systems are professional-only.
• You need to terminate heavy battery, starter, winch or inverter cable.
• A crimped joint is getting hot, discoloured or causing a fault that comes and goes.

Related questions

Q: Can I crimp terminals with pliers? A: You can squash a terminal with pliers, but it won’t compress evenly and often loosens with vibration. A ratchet crimper with the right die makes a consistent crimp every time.

Q: Should I solder a crimp as well? A: It depends on the job. Many auto electricians see a soldered and crimped joint as the best for conductivity and long life, but a correct crimp made with the right tool is reliable on its own for most jobs. If you do solder, keep the solder to the crimped area and support the cable behind the terminal, because solder that wicks up the strands makes a stiff spot where vibration can crack the wire. Sealed connectors such as Deutsch use solid contacts with a four-indent crimp and normally aren’t soldered.

Q: What does the colour on a crimp terminal mean? A: It shows the wire size the terminal suits: red for 0.5 to 1.5 mm², blue for 1.5 to 2.5 mm² and yellow for 4 to 6 mm².

Q: Do I need heat shrink over crimp terminals? A: Inside the cabin it’s optional on insulated terminals. Under the bonnet, under the vehicle, on a trailer or anywhere wet, adhesive-lined heat shrink keeps water and corrosion out of the joint.

Q: How do I connect a new accessory to power safely? A: Run it from a fused source, with the fuse close to the battery and rated to protect the cable. (see Where should the fuse go when wiring an accessory?)

Sources

1. RS Components (RND Connect), insulated crimp terminal datasheet – colour code red 0.5–1.5 mm² (22–16 AWG), blue 1.5–2.5 mm² (16–14 AWG), yellow 4–6 mm² (12–10 AWG). https://docs.rs-online.com/c5cd/A700000013591123.pdf (checked October 2026)
2. Tycab, automotive cable catalogue – single-core auto cable stranding and copper areas (14/0.32 1.13 mm², 23/0.32 1.84 mm², 36/0.32 2.90 mm², 57/0.32 4.59 mm²). https://www.tyree.nz/wp-content/uploads/2019/09/Automotive-Comp.pdf (checked October 2026)
3. Molex, “Introduction to Crimp Technology” (application tooling) – parts of a crimp (conductor crimp, insulation crimp, bellmouth, conductor brush), common defects, pull testing. https://www.molex.com/content/dam/molex/molex-dot-com/en_us/pdf/general/987652-5181.pdf (checked October 2026)
4. NASA, NASA-STD-8739.4A “Workmanship Standard for Crimping, Interconnecting Cables, Harnesses, and Wiring” – stranded wire for crimped contacts; full-cycle ratcheting crimp tools; pull testing. https://nepp.nasa.gov/files/27631/nstd87394a.pdf (checked October 2026)
5. Cirris, “Crimp pull testers: pullout force per wire size” – summary of UL 486A minimum pull-out forces for terminals (18 AWG 20 lbf, 16 AWG 30 lbf, 14 AWG 50 lbf, 12 AWG 70 lbf; converted to newtons and kg). https://cirris.com/crimp-pull-testers-pullout-force-per-wire-size/ (checked October 2026)
6. AWG to mm² conversions (18 AWG 0.82 mm², 16 AWG 1.31 mm², 14 AWG 2.08 mm², 12 AWG 3.31 mm²) – standard American Wire Gauge definitions.
7. Hella, heat shrink insulated crimp terminal connectors – red, blue and yellow terminals, with yellow for 4 to 6 mm² cable. https://www.hella.co.nz/en/products/accessories/connectors/heat-shrink-insulated-crimp-terminal-connector.html (checked October 2026)
8. Wiltronics, 4mm twin core auto cable – “4mm” auto cable is 23/0.32 stranding (about 1.85 mm²). https://www.wiltronics.com.au/product/52830/4mm-twin-core-auto-cable (checked October 2026)

Quick answer

Wear gloves and safety glasses, disconnect the negative terminal first and then the positive, and scrub the white, blue or green deposits off the posts and clamps with a battery terminal brush. A solution of bicarbonate of soda (bicarb) and water helps neutralise acid residue. Rinse with a little clean water, dry everything, reconnect positive first and negative last, then protect the terminals with a terminal spray or grease. If the corrosion keeps coming back, have the battery and charging system checked.

Is this a DIY job?

• Difficulty: Easy
• Time: 15 to 30 minutes
• Tools: battery terminal brush (or a stiff wire brush), spanner (often 10 mm), bicarb soda, water, old toothbrush, rags, gloves, safety glasses
• Skills: basic hand tools

Step by step

1. Protect yourself. Wear gloves and safety glasses. The deposits contain acid residue. Take off rings and metal watch bands.
2. Check your manual. Note any radio code or reset steps, and whether your car needs special care when the battery is disconnected. (see How do I replace a car battery?)
3. Switch everything off. Ignition off, key out.
4. Disconnect the negative (−) terminal first, then the positive (+). Tuck the clamps away from the posts.
5. Mix a cleaning solution. About a tablespoon of bicarb soda in a cup of warm water is a common home mix.
6. Scrub the clamps and posts. Dip the brush in the solution and scrub. Fizzing means the bicarb is reacting with acid residue; keep applying until the fizzing stops, which tells you the acid has been neutralised. Use the terminal brush’s post end on the battery posts and the clamp end inside the clamps. If the battery has removable vent caps, make sure they’re fitted tightly first, and don’t let solution run into the cells.
7. Rinse and dry. Wipe with a rag dampened in clean water, then dry thoroughly. Keep runoff away from paint and wiring where you can, and rinse any splashes off the paint.
8. Check the cables. Pull back the boot on each clamp. If the copper under the insulation is green or the cable is stiff and swollen, the corrosion has spread up the cable and the cable or clamp should be replaced.
9. Reconnect positive (+) first, then negative (−) last. Tighten firmly, but don’t over-tighten soft lead posts.
10. Protect the terminals. Spray with terminal protector or apply a thin coat of terminal grease.
11. Start and check. Start the car and check for warning lights. Reset radio, clock and windows if needed.

Why bicarb soda works

Most terminal corrosion on a lead-acid battery comes from battery acid getting out. When a battery is overcharged or runs hot, the acid inside can boil and vent, and the acid that escapes settles on the terminals and clamps and eats into them. Bicarb soda is a mild alkali. It reacts with the acid residue and turns it into harmless salts, water and carbon dioxide (the fizz), so the residue is inert and can be wiped and rinsed away safely. Scrubbing alone moves the acid around; bicarb neutralises it.

If the battery has boiled acid out, cleaning fixes the symptom, not the cause. Have the charging system checked, because a high charging voltage will keep boiling the battery.

Specs table

What the corrosion is telling you

What you see	What it usually means
Light white or grey powder	Normal minor corrosion from acid vapour; clean and protect
Heavy build-up that keeps returning	Battery venting or leaking; possible overcharging; get battery and charging tested
Green corrosion on clamps and up the cable	Copper corrosion; clean and check whether the cable or clamp needs replacing
Wet or crusty battery case, swelling	Leaking or failing battery: replace it
Corrosion and slow cranking or flickering lights	Corrosion is likely causing a poor connection

What you’ll need

• battery terminal brush
• battery terminal protector spray or terminal grease
• battery terminal clamp (if a clamp is damaged)
• battery cable (if corrosion has spread up the cable)
• safety glasses and nitrile gloves

When to call an auto electrician

• Corrosion has spread under the cable insulation, or cables are swollen or brittle.
• Corrosion comes back quickly. The battery may be leaking, or the charging voltage may be too high. (see How do I know if my alternator needs replacing?)
• The battery case is swollen, cracked or wet, or smells of rotten eggs.
• Your car needs battery registration or has a battery sensor on the negative terminal that might be damaged.

Related questions

Q: Can I clean battery terminals without disconnecting them? A: It’s safer to disconnect them. A brush or spanner bridging the positive terminal to metal can cause a dangerous short. Disconnecting also lets you clean the contact surfaces properly.

Q: Can I use Coca-Cola to clean battery terminals? A: It’s a popular trick, but it leaves sticky residue. Bicarb soda and water neutralise acid and rinse off cleanly.

Q: What causes battery terminal corrosion? A: Battery acid escaping and reacting with the metal posts and clamps. A little acid vapour causes light corrosion; heavy corrosion usually means the battery has been overcharged or overheated and boiled acid out. A leaking case or loose terminals can make it worse.

Q: Will corroded terminals stop my car starting? A: Yes. Corrosion adds resistance, which can cause slow cranking, clicking or no start at all. (see Is it my starter motor or my battery?)

Sources

1. RACV, “Car battery replacement” – battery management systems and registration on some vehicles. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)
2. Planet Ark, Recycling Near You, “Recycling lead-acid batteries” – lead-acid batteries are hazardous; disposal guidance. https://recyclingnearyou.com.au/car-batteries (checked October 2026)
3. Rolls Battery, “Cleaning – batteries and terminals” – baking soda and water solution for cleaning, vent caps closed first, rinse with water, wire-brush terminals and re-apply protective grease. https://support.rollsbattery.com/en/support/solutions/articles/646-cleaning-batteries-terminals (checked October 2026)
4. Technical review, Ozautoelectrics (October 2026) – bicarb soda reacts with acid residue from batteries that have boiled acid out, neutralising it so it no longer corrodes the terminals. Consistent with standard acid–base chemistry (sodium bicarbonate + sulphuric acid → sodium sulphate, water and carbon dioxide).

Quick answer

Find the 16-pin diagnostic port under the dash on the driver’s side, plug in the scanner (or a Bluetooth adaptor paired to an app), switch the ignition on and choose “read codes”. Write down every code and any freeze-frame data before you do anything else. A code tells you which system has seen a problem, not which part to replace, and clearing it doesn’t fix the fault.

Is this a DIY job?

• Difficulty: Easy
• Time: 5 to 15 minutes to read; longer to research what the codes mean
• Tools: OBD2 code reader or Bluetooth OBD2 adaptor with a phone app, pen and paper (or phone camera), owner’s manual
• Skills: following on-screen menus

Anyone can read engine codes. Working out the cause, and anything to do with airbags, ABS or hybrid systems, is a job for a professional with a full diagnostic tool.

Which cars have an OBD port?

Australian Design Rule 79/01 brought in on-board diagnostic (OBD) requirements for light vehicles (up to 3.5 t GVM). It applied to all petrol vehicles built from 1 January 2006 and all diesel vehicles built from 1 January 2007. New models were covered a year earlier: petrol from 2005, diesel from 2006. As first made, the rule exempted vehicles running on LPG or natural gas (including dual-fuel) from the OBD part. Many earlier cars also have the port, but what a generic scanner can read on them varies.

Australian rules follow the European version of OBD (often called EOBD). It uses the same 16-pin connector and the same generic code format as the American OBD2 system, so a standard OBD2 scanner works on most of these cars.

Step by step

1. Park safely. Park on level ground, handbrake on, in Park or neutral. Don’t use the scanner while driving.
2. Find the port. Look under the dash on the driver’s side, usually near the steering column, behind the fuse panel cover or near the bonnet release. If you can’t find it, check the owner’s manual.
3. Plug in with the ignition off. Push the scanner or adaptor in firmly. It only fits one way.
4. Switch the ignition on. Turn the key to “on” (or press start without your foot on the brake) so the dash lights up. Some scanners also work with the engine running. Follow the scanner’s instructions.
5. Connect the app (Bluetooth adaptors only). Pair the adaptor with your phone and open the app. Choose your vehicle if the app asks.
6. Read the codes. Choose “read codes” or “DTCs”. Note whether each code is stored (confirmed), pending, or permanent, if the scanner shows that.
7. Record everything. Write down or photograph every code, its description and any freeze-frame data (engine speed, temperature and so on when the fault was set). This is the evidence a technician needs.
8. Check readiness monitors. Many scanners have an “I/M readiness” or “monitor status” screen. It shows which emission self-tests have finished. Record it too.
9. Look up the codes. Use the scanner’s built-in library or the vehicle maker’s information. Read the code as “where to start looking”, not “replace this part”. A code for an oxygen sensor, for example, can be caused by a wiring fault, an air leak or a fuel problem.
10. Don’t clear the codes yet. Clearing turns the light off but doesn’t repair anything. It also wipes the freeze-frame data and resets the readiness monitors. If the fault is still there, the light will come back.
11. Unplug the scanner with the ignition off. Don’t leave a Bluetooth adaptor plugged in long-term unless it’s designed for it. Some keep drawing power and can flatten the battery. (see Why does my car battery keep going flat?)

Specs table

Reading a fault code (for example P0301)

Position	What it tells you	Values
1st character	System	P = powertrain (engine, transmission, emissions); B = body (airbags, air conditioning, seats); C = chassis (ABS, steering, suspension); U = network (communication between control modules)
2nd character	Who defined the code	0 = generic code, same meaning on every make; 1 = manufacturer-specific code, meaning set by the vehicle maker
3rd to 5th characters	The specific fault	Look up the full code for the exact meaning

Codes beginning with other second digits (2 or 3) exist too. Whether they’re generic or manufacturer-specific depends on the code range, so look them up rather than assuming.

What the engine warning light is telling you

Light	What it usually means	What to do
Comes on and stays on	The OBD system has detected a fault	Read the codes and get it checked soon
Flashing	A serious fault, such as a misfire that can damage the catalytic converter	Avoid high speed and heavy loads; get it checked as soon as possible
Went out by itself	The system no longer sees the fault	Codes may still be stored; read them at your next chance

Generic scanner vs professional diagnostic tool

Job	Basic OBD2 reader or Bluetooth adaptor	Professional diagnostic tool
Read and clear generic engine codes (P0)	Yes	Yes
Live engine data and readiness monitors	Often	Yes
Manufacturer-specific engine codes	Sometimes	Usually
Airbag/SRS, ABS, body and network modules	Rarely (some readers cover ABS and airbag codes on certain makes)	Usually
Hybrid and EV high-voltage systems	No	Needs maker-level tools and training
Coding, resets and calibrations after repairs	No	Often

A generic OBD2 connection is mainly limited to engine and emissions data. Reaching the other modules, running tests and doing relearns or coding needs an enhanced or maker-level tool.

What you’ll need

• OBD2 code reader or Bluetooth OBD2 adaptor
• OBD2 extension cable (if the port is hard to reach)

When to call an auto electrician

• The engine warning light is flashing, or the car is running badly.
• The airbag/SRS or ABS warning light is on. These are safety systems: don’t clear the codes or drive on assuming it’s fine. Airbag work is professional only.
• The car is a hybrid or EV. High-voltage systems are professional only, and their faults need maker-level diagnostic tools.
• The code points to wiring, a network (U) fault or several modules at once.
• The light keeps coming back after a repair.
• You need the car to pass a roadworthy. Roadworthy inspections don’t read the car’s computer, but they do check that warning lights such as the engine, ABS and airbag lights go out after start-up, and they include a brake test. Clearing codes just before an inspection doesn’t fix anything, and the light is likely to come back on.

Related questions

Q: Does clearing a fault code fix the problem? A: No. Clearing only turns the warning light off and erases the stored data. If the fault is still there, the code and the light will come back, and the information a technician would have used is gone.

Q: Can I use a cheap Bluetooth OBD2 adaptor? A: For reading generic engine codes and live data, often yes. They usually can’t read airbag, ABS or most body modules, so they won’t show every fault on the car.

Q: Why won’t my scanner connect? A: Check the ignition is on, the plug is fully seated and the scanner supports your vehicle. A blown fuse feeding the diagnostic port can also stop it powering up. (see How do I check and replace a blown fuse?)

Q: What are readiness monitors? A: They’re self-tests the engine computer runs on emission systems such as the catalytic converter and oxygen sensors. Clearing codes or disconnecting the battery resets them, and they only complete after the car has been driven through the right conditions.

Q: Is a diagnostic scan worth paying for? A: If the light keeps returning, or the fault involves airbags, ABS or hybrid systems, a professional scan goes much deeper than a basic reader.

Sources

1. Federal Register of Legislation, Vehicle Standard (Australian Design Rule 79/01 – Emission Control for Light Vehicles) 2005 – applies to M1 and N1 vehicles up to 3.5 t GVM; petrol new models from 1 January 2005, all petrol vehicles from 1 January 2006; diesel new models from 1 January 2006, all diesel vehicles from 1 January 2007; OBD requirements and the exemption for LPG and natural gas (mono-fuel and bi-fuel) vehicles (clause 5.5). https://legislation.gov.au/F2005L04080/asmade/2005-12-15/text/original/pdf/1 (checked October 2026)
2. Vehicle Service Pros, “Different types of diagnostics: an overview of scan tool options” – basic code readers and generic OBD-II are limited to engine/emissions data; enhanced tools add ABS, SRS and other modules, bidirectional tests, coding and relearns. https://www.vehicleservicepros.com/distribution/tool-distributor/article/12066051/different-types-of-diagnostics-an-overview-of-scan-tool-options (checked October 2026)
3. US Environmental Protection Agency, “On-Board Diagnostics (OBD) – Check Engine Light” fact sheet (EPA420-F-02-016) – steady vs flashing warning light; light turns off by itself when the fault is corrected; scan tool connects under the dash. https://19january2021snapshot.epa.gov/sites/static/files/2013-08/documents/420f02016.pdf (checked October 2026)
4. New York State DMV, “What do you mean my car’s not ready?” – readiness monitors; clearing codes with a scan tool or disconnecting the battery leaves monitors incomplete; drive cycles. https://dmv.ny.gov/brochure/what-do-you-mean-my-cars-not-ready (checked October 2026)
5. Haynes, “OBD fault codes” – first letter P, B, C, U system meanings; second character 0 generic, 1 manufacturer-specific. https://uk.haynes.com/de/pages/odb-fault-codes-car (checked October 2026)
6. SAE J1962 / ISO 15031-3 (standard) – 16-pin diagnostic connector located within reach of the driver’s seat.
7. Bosch (OTC), OBD 1200 code reader product sheet – reads ABS and airbag/SRS codes on certain makes and years only. https://otctools.com/sites/default/files/102019_145_obd_1200_bosch.pdf (checked October 2026)

Quick answer

Switch the ignition off, find the right fuse using the chart in your owner’s manual or on the fuse box lid, pull it out with the fuse puller, and look through the plastic: a broken metal strip means it’s blown. Replace it with a fuse of exactly the same rating (the number on top and the colour). If the new fuse blows again, there’s a fault in that circuit that needs finding: never fit a bigger fuse.

Is this a DIY job?

• Difficulty: Easy
• Time: 5 to 15 minutes
• Tools: owner’s manual, fuse puller (often clipped inside the fuse box), torch, test light or multimeter (optional)
• Skills: none

Checking and replacing a blade fuse is one of the simplest car jobs. Finding why a fuse keeps blowing is harder and may need an auto electrician.

Step by step

1. Switch off. Ignition off, key out, and switch off the item that stopped working.
2. Find the fuse boxes. Most cars have at least two: one under the bonnet and one inside the cabin (under the dash, in the side of the dash, or behind a panel in the footwell or glovebox). Some have more, including one in the boot. Your owner’s manual shows where.
3. Find the right fuse. Use the chart in the manual or on the inside of the fuse box lid. Fuses are labelled by position, rating and the circuit they protect (for example “CIG”, “RADIO”, “P/W”).
4. Pull the fuse out. Use the plastic fuse puller, or fine-nose pliers, gripping the plastic body. Pull straight out.
5. Check it. Hold it up to the light. A good fuse has an unbroken metal strip between the two blades. A blown fuse has a gap or a melted, blackened strip. If you can’t tell, test it: with a multimeter on continuity or resistance, a good fuse reads close to zero ohms. Many blade fuses also have small test points on top, so you can test them in place with a test light (ignition on for circuits that are only live with the ignition).
6. Fit an identical replacement. Same type (micro, mini, standard or maxi), same rating (number on top), same colour. Push it fully into the slot.
7. Test the circuit. Switch on and check the item works.
8. If it blows again straight away, stop replacing fuses. There’s a short circuit or an overload in that circuit.
9. Replace your spare. Many fuse boxes have spare fuses clipped inside. Replace any you use.

Checking a relay

Relays are the larger plug-in cubes in the fuse box. They switch high-current items like headlights, horns, fans and fuel pumps. A simple check: with the ignition off, swap the suspect relay with an identical relay (same part number) from a circuit you can test, such as the horn. If the fault moves with the relay, the relay is faulty. If you’re not sure two relays are identical, don’t swap them. (see How do I wire a 12V relay (pins 30, 85, 86, 87)?)

Specs table

Standard blade fuse colours (regular, mini and micro blade fuses)

Rating	Colour
1 A	Black
2 A	Grey
3 A	Violet
4 A	Pink
5 A	Tan
7.5 A	Brown
10 A	Red
15 A	Blue
20 A	Yellow
25 A	Clear (natural)
30 A	Green
40 A	Orange

Not every rating is made in every size, but where a rating exists the colour is the same.

Maxi fuses use a different colour code. For example, a 50 A maxi fuse is red and a 60 A maxi is blue. Always go by the number printed on the fuse, not just the colour.

Fuse types by size

Type	Typical use
Micro2 / Micro3	Many newer vehicles
Mini blade	Most cars from the 1990s on
Standard (ATO/ATC) blade	Older cars, many accessories and trailers
Maxi blade	High-current circuits under the bonnet
Bolt-in or cartridge fuses	Main supply and high-current circuits (leave to a professional)

What you’ll need

• mini blade fuse kit / standard blade fuse kit / micro blade fuses (whichever your car uses)
• fuse puller
• 12V test light or digital multimeter
• automotive relay (if a relay has failed; match the part number)

When to call an auto electrician

• A fuse blows again after replacement. There’s a short or overload to find.
• The blown fuse protects the airbags/SRS, ABS, engine management or a module. Don’t keep replacing these: get the fault diagnosed.
• A large bolt-in, cartridge or main fuse has blown. These protect major circuits and often point to a serious fault.
• Fuses, relays or the fuse box show signs of melting or heat damage.
• It’s a hybrid or EV and the fault involves the high-voltage system. Never touch orange cables or high-voltage fuses.

Related questions

Q: Can I use a higher-rated fuse if I don’t have the right one? A: No. The fuse protects the wiring. A higher-rated fuse can let the wiring overheat and start a fire before the fuse blows. Never replace a fuse with wire, foil or any other metal object, even to get home.

Q: Can I use a fuse from another circuit temporarily? A: Only if it’s exactly the same rating and from a circuit you don’t need, such as the cigarette lighter. Replace it with the correct fuse as soon as you can, and never borrow from safety systems.

Q: Why does my fuse look fine but the circuit doesn’t work? A: Fuses can crack internally where you can’t see it, so test it with a multimeter or test light. If the fuse is fine, check the relay, switch, wiring and the item itself.

Q: Where’s my car’s fuse box? A: Most cars have one under the bonnet and one in the cabin, and some have one in the boot. The owner’s manual shows the locations and what each fuse does.

Sources

1. Littelfuse, ATO and MAXI blade fuse datasheet (via Farnell) – blade fuse colour codes by rating; maxi colour code differs. https://www.farnell.com/datasheets/82316.pdf (checked October 2026)
2. ISO 8820-3 – Road vehicles, fuse-links, Part 3: fuse-links with tabs (blade type). Referenced as the standard behind the colour code; not quoted.
3. Volvo Cars Australia, “Replacing a fuse” (V90 owner information) – replace with the same colour and amperage; a higher-rated fuse or a foreign object can damage the electrical system and cause a fire. https://www.volvocars.com/au/support/car/v90/article/97f7da007063b1e3c0a8015164d3df7a/ (checked October 2026)
4. Kia owner’s manual, “Fuse replacement” – same rating only; a fuse that blows again means an electrical problem; never use wire or foil in place of a fuse. https://ownersmanual.kia.com/full_webhelp/KA4/2024/en_US/topics/t00732.html (checked October 2026)

Quick answer

Connect red to the flat battery’s positive, red to the good battery’s positive, black to the good battery’s negative, and the last black clamp to bare metal on the flat car’s engine or body, away from the battery. Start the good car, wait a few minutes, then start the flat car. Remove the leads in the reverse order. Check your owner’s manual first: some cars have dedicated jump points, and some hybrids and EVs have specific rules.

Is this a DIY job?

• Difficulty: Easy
• Time: 10 to 20 minutes
• Tools: jumper leads (heavy duty) or a portable jump starter, safety glasses, gloves, owner’s manuals for both cars
• Skills: following a sequence carefully

Jump starting is a normal roadside job, but getting the order wrong can cause sparks, damage electronics or, rarely, make a battery explode. Take your time.

Step by step

1. Check the manuals. Find the jump points for both cars. Some cars have remote jump terminals under the bonnet because the battery is in the boot or under a seat. Check whether either car is a hybrid or EV and what the manual allows.
2. Check the batteries. Don’t jump start if either battery is cracked, leaking, swollen or badly corroded. Both systems must be the same voltage (almost all cars are 12V).
3. Position the cars. Bring the good car close enough for the leads to reach, without the cars touching. Handbrakes on, automatics in Park, manuals in neutral. Both ignitions fully off, and switch off lights, radio and A/C.
4. Protect yourself. Safety glasses and gloves on, rings and metal watch bands off. No smoking or flames. Keep leads away from fans and belts.
5. Connect red to the flat battery’s positive (+).
6. Connect the other red clamp to the good battery’s positive (+).
7. Connect black to the good battery’s negative (−).
8. Connect the last black clamp to bare metal on the flat car, such as an unpainted bolt or bracket on the engine, well away from the battery and moving parts. Don’t connect it to the flat battery’s negative post: the final connection can spark, and batteries can give off hydrogen gas.
9. Start the good car and let it run for a few minutes.
10. Start the flat car. Crank for no more than about 5 seconds at a time. If it doesn’t start, wait a couple of minutes before trying again. If it still won’t start after a few tries, the problem may not be the battery. (see Is it my starter motor or my battery?)
11. Remove the leads in reverse order: black from the flat car’s earth point, black from the good battery, red from the good battery, red from the flat battery. Don’t let the clamps touch each other or any metal.
12. Keep the jumped car running for a while, then have the battery charged properly and tested. Driving alone often won’t fully recharge a flat battery, and a battery that went flat for no clear reason may be failing or have a drain. (see Why does my car battery keep going flat?)

Using a portable jump starter

Follow the pack’s instructions. Most connect red to positive and black to an earth point or the negative post, with built-in reverse-polarity protection. Keep packs charged and stored out of direct sun, and avoid leaving lithium packs in a hot parked car. Don’t use a pack that is swollen, damaged or overheating.

Specs table

Connection order

Step	Clamp	Connect to
1	Red	Flat battery positive (+)
2	Red	Good battery positive (+)
3	Black	Good battery negative (−)
4	Black	Bare metal earth point on the flat car, away from the battery

Removal order: 4, 3, 2, 1 (the reverse).

What you’ll need

• jumper leads heavy duty or portable jump starter
• safety glasses
• smart battery charger (to recharge the battery properly afterwards)

When to call an auto electrician

• Either battery is damaged, leaking, swollen or smells of rotten eggs.
• The car won’t start even with a good jump.
• The car needs jump starting regularly.
• Warning lights stay on after the car starts.
• You’re not sure where to connect on a hybrid, EV or car with a battery in the boot. Never connect to or touch high-voltage parts or orange cables. Don’t use a hybrid or EV as the donor car unless its manual says that’s allowed.
• If you’re not confident, call your roadside assistance provider.

Related questions

Q: Why not connect the last clamp to the flat battery’s negative post? A: The last connection often makes a small spark. Batteries can give off hydrogen gas, so the spark should happen away from the battery, on bare metal on the engine or body.

Q: How long should I leave the car running after a jump start? A: Long enough to be sure it keeps running, then have the battery charged with a proper charger and tested. A short drive won’t fully recharge a flat battery.

Q: Can I jump start a hybrid? A: Usually, yes, using the 12V jump points shown in the manual. The 12V battery powers up the system; you’re not jump starting the high-voltage battery. Follow the manual exactly.

Q: Can jump starting damage my car? A: Done correctly, it rarely does. Reverse polarity, clamps touching, or connecting with ignitions on can damage electronics. Some vehicle manuals give specific warnings, so check yours.

Sources

1. RACV, “Car battery guide: how they work, when to replace them, and how to jump-start” – connection order; last clamp on unpainted metal on the flat car, not the flat battery’s negative; remove in reverse order. https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
2. RAC (UK), “How to jump start a car in 10 steps” – crank limits, damaged battery warnings, hybrid donor caution. https://www.rac.co.uk/drive/advice/car-maintenance/how-to-jump-start-a-car/ (checked October 2026)
3. ACCC Product Safety Australia, “Lithium-ion batteries guide” – store out of direct sunlight, not in hot places such as parked vehicles; don’t use swollen or damaged batteries. https://www.productsafety.gov.au/consumers/be-safe-around-the-home/safely-use-batteries-and-technology/lithium-ion-batteries-guide (checked October 2026)

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)

1. 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.
2. Look before you touch. Safety glasses on. Check the case for swelling, cracks, leaks or heavy corrosion. If you find any of these, stop.
3. 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?)
4. Measure. Red probe on the positive (+) post, black probe on the negative (−) post. Touch the lead posts or clamp bolts, not the plastic covers.
5. 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)

6. Keep clear of moving parts. Hands, hair, clothing and leads away from the belt and fan.
7. 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)

8. 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

9. 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.
10. Connect the tester’s clamps red to positive, black to negative, directly on the battery posts.
11. 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.
12. 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

13. 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

14. 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?)
15. 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.

Related questions

Q: What voltage should a car battery read? A: About 12.6 V when fully charged and rested overnight with the engine off. With the engine running, most cars read roughly 13.5 to 14.8 V because the alternator is charging.

Q: Can a battery show 12.6 V and still be bad? A: Yes. Voltage only shows the state of charge. A worn battery can show full voltage with no load, then collapse when you try to start the car. A load test or electronic tester shows its real condition.

Q: How long should I wait after driving to test my battery? A: Overnight is best. Lead-acid batteries need at least four hours of rest, and battery makers suggest 24 hours, for an accurate open-circuit reading.

Q: How long does a car battery last? A: RACV gives about three to five years for a standard lead-acid battery and five to seven for AGM, though how you drive and the climate make a big difference. (see What’s the difference between flooded, EFB, AGM and lithium car batteries?)

Q: What does the coloured “magic eye” on top of my battery mean? A: It’s a hydrometer that shows the condition of one cell only, so it’s a rough guide. A multimeter or battery tester gives a more reliable picture.

Sources

1. 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)
2. 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)
3. 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)
4. 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)
5. 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)
6. 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)
7. 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)
8. 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)
9. 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)

Quick answer

Switch everything off, disconnect the negative (−) terminal first, then the positive (+), undo the hold-down and lift the old battery out. Fit a battery of the same size, type and rating, secure it, then connect positive first and negative last. If your car has stop-start it needs an EFB or AGM battery, and some cars also need the new battery registered with a scan tool.

Is this a DIY job?

• Difficulty: Easy on most cars; Medium if the battery is under a seat, in the boot or needs registration
• Time: 20 to 45 minutes
• Tools: spanners or sockets (often 10 mm, but check), terminal brush, safety glasses, gloves
• Skills: basic hand tools and careful lifting

On most cars with the battery under the bonnet, this is a straightforward DIY job. Check two things before you start: whether your car needs battery registration (see step 2), and what type of battery it uses (see the specs table).

Step by step

1. Get the right battery. Read the label on your old battery or check the owner’s manual. Match the physical size, terminal layout (which side the positive post is on), type and cold cranking amps (CCA). Never fit a lower type than the original: a stop-start car that came with an AGM battery needs an AGM replacement.
2. Check your manual for extras. Some cars need the new battery registered (coded) to the battery management system with a scan tool. If that’s skipped, stop-start and charging may not work properly. Also check whether you’ll need a radio code and how to reset power windows after the battery has been disconnected.
3. Gear up and make it safe. Wear safety glasses and gloves. Take off rings and metal watch bands. Park on level ground, switch off the ignition and all accessories, and take the key out. No smoking or flames: batteries can give off hydrogen gas.
4. Disconnect the negative (−) terminal first. It’s usually black and marked “−” or “NEG”. Loosen the clamp nut, twist the clamp off the post and tuck it away so it can’t spring back and touch the post.
5. Disconnect the positive (+) terminal. It’s usually red, often under a plastic cover. Loosen it and lift it off. Don’t let your spanner touch any metal part of the car while it’s on the positive terminal.
6. Remove the hold-down. Undo the clamp, bar or bracket that holds the battery in place. If there’s a small vent tube on the side of the battery (common on batteries in the boot or cabin), unclip it.
7. Lift out the old battery. Batteries are heavy. Keep it upright, use the handle if it has one, and lift with your legs. Put it somewhere it can’t tip over.
8. Clean up. Brush any corrosion off the terminal clamps and the tray. Check the cables for cracks, swelling or green corrosion under the insulation. Replace damaged cables before fitting the new battery.
9. Fit the new battery. Sit it in the tray the same way round as the old one, so the positive post lines up with the positive cable. Refit the vent tube if there is one.
10. Secure the hold-down. The battery must not move when you push it. A loose battery can short out or crack under vibration.
11. Connect the positive (+) terminal first. Push the clamp fully down on the post and tighten it firmly. Don’t over-tighten: lead posts are soft. Refit the red cover.
12. Connect the negative (−) terminal last. Tighten it the same way. A small spark as it touches is normal. Spray both terminals with terminal protector.
13. Start and check. Start the car and check that no warning lights stay on. Reset the clock, radio presets and window auto-up if needed. Some cars idle a little oddly for the first few minutes while the engine computer relearns.
14. Register the battery if your car needs it. If your manual or the battery supplier says registration is required, have it done with a suitable scan tool.
15. Recycle the old battery. Don’t put it in a household bin. Battery retailers, many workshops, scrap metal dealers and council drop-off points accept lead-acid batteries.

Using a memory saver

A memory saver plugs into the OBD port or 12V socket and keeps a little power on so you don’t lose radio and settings. If you use one, remember the battery cables are still live. Keep the positive clamp wrapped or covered so it can’t touch the body. If you’re not confident, it’s safer to skip the memory saver and reset things afterwards.

Specs table

Which battery type?

Type	What it is	Typically fitted to
Conventional flooded (wet cell)	Standard lead-acid with liquid electrolyte	Older cars and many cars without stop-start
EFB (Enhanced Flooded Battery)	Flooded battery built to handle more frequent starts	Many entry-level stop-start cars
AGM (Absorbent Glass Mat)	Electrolyte held in glass mats; sealed and spill-resistant	Stop-start cars with brake energy recovery, high-demand vehicles, batteries in cabin or boot
Lithium (12V)	Lithium starting battery	Some hybrids, EVs and performance vehicles: only where the maker specifies

Rule of thumb: replace like for like. Don’t fit a conventional battery where an EFB or AGM was fitted at the factory, and always replace AGM with AGM. If you upgrade from EFB to AGM, the car may need the new battery type set in its system.

Terminal order

Job	First	Last
Removing	Negative (−)	Positive (+)
Fitting	Positive (+)	Negative (−)

Why: once the negative is off, touching the car’s body with a spanner on the positive terminal can’t cause a short.

What you’ll need

• car battery (matched to your vehicle; AGM car battery or EFB car battery for stop-start)
• battery terminal brush
• battery terminal protector spray
• battery terminal clamp (if the old ones are damaged)
• memory saver (optional)
• safety glasses and nitrile gloves

When to call an auto electrician

• Your car needs battery registration or coding and you don’t have a suitable scan tool.
• The battery is hard to get to (under a seat, behind a wheel arch liner, under the floor).
• The cables or terminals are badly corroded, melted or cracked.
• The new battery goes flat again within days or weeks. That points to a charging fault or a parasitic drain.
• Warning lights stay on after the battery change.
• It’s a hybrid or EV. You can often replace the 12V battery yourself if the manual allows it, but never touch the high-voltage battery or any orange cables. Many hybrid 12V batteries are AGM and are often in the boot or under a seat with a vent tube.

Related questions

Q: Can I fit a normal battery in a car with stop-start? A: No. Stop-start puts far more starts and deep cycles on the battery. A conventional battery will wear out quickly and the stop-start system may stop working. Fit EFB or AGM, matching what the factory fitted. (see What’s the difference between flooded, EFB, AGM and lithium car batteries?)

Q: Why do you take the negative terminal off first? A: The car’s body is connected to the negative terminal. If you undo the positive first and your spanner touches the body, you create a direct short. Taking the negative off first removes that risk.

Q: What is battery registration? A: On some cars, the battery management system needs to be told a new battery has been fitted so it can adjust charging. It’s done with a scan tool. Skipping it can affect stop-start and shorten the new battery’s life.

Q: How do I know what size battery my car needs? A: Check the label on the old battery, the owner’s manual or a battery fitment guide for your make and model. Match the size, terminal layout, type and CCA.

Q: Will I lose my radio and settings? A: You may lose radio presets, the clock and window auto-up settings. Some older radios need a security code, which is usually in the owner’s manual or service book.

Sources

1. RACV, “Car battery replacement” – some vehicles have a battery management system that requires new batteries to be registered. https://racv.com.au/on-the-road/roadside-assistance/car-battery-replacement.html (checked October 2026)
2. VARTA, “The right code of the BEM for battery replacement” – which makes need active registration and the effect on stop-start if skipped. https://www.varta-automotive.com/en/knowledge/articles/article-details/the-right-code-of-the-bem-for-battery-replacement (checked October 2026)
3. Banner Batteries, “How-to: registering start-stop batteries” – open and closed systems; effects of not registering on some makes; AGM must be replaced with AGM; an EFB-to-AGM upgrade must be configured; never replace EFB or AGM with a conventional battery. https://www.bannerbatterien.com/en/Battery-knowledge/7-HOW-TO-Registering-the-battery (checked October 2026)
4. VARTA, “AGM technology” – AGM for start-stop with regenerative braking, high electrical demand and hybrids; EFB for entry-level start-stop. https://www.varta-automotive.com/en-gb/knowledge/technology/agm (checked October 2026)
5. Planet Ark, Recycling Near You, “Recycling lead-acid batteries” – don’t put in bins; where to take them; about 97% of materials recyclable. https://recyclingnearyou.com.au/car-batteries (checked October 2026)

Quick answer

For most car jobs you only need three settings: DC volts to check the battery and charging system, continuity (the beep setting) to check fuses and wires, and ohms to measure resistance. Put the black lead in the COM socket and the red lead in the V/Ω socket, select DC volts, and touch red to positive and black to negative: a healthy, rested 12V battery reads about 12.6 V. Only test resistance or continuity with the power off, and never touch the probes across a battery while the leads are in the amps (A) socket.

Is this a DIY job?

• Difficulty: Easy
• Time: 5 to 15 minutes per test
• Tools: digital multimeter, test leads (probes and alligator clips), safety glasses
• Skills: reading the meter dial and keeping track of positive and negative

A multimeter is a safe tool on a car’s 12V system as long as you use the right setting for each test. Leave airbag (SRS) wiring and anything on a hybrid or electric vehicle’s high-voltage system alone: those are jobs for a qualified technician.

Know your meter first

Before you start, find these on your meter. The labels vary a little between meters, so check the manual if anything looks different.

• COM socket: the black lead always goes here.
• V/Ω socket (often marked VΩ or VΩmA): the red lead goes here for volts, ohms and continuity.
• A or 10A socket: for measuring current only. The red lead goes here only when you’re deliberately measuring amps with the meter wired in series.
• DC volts (V with a straight line, sometimes V⎓ or DCV): for anything on a car’s 12V system. AC volts (V~) is not used for battery tests.
• Ω (ohms): resistance.
• Continuity: usually a sound-wave or diode symbol that shares the Ω position.

Auto-ranging meters pick the range for you. On a manual-ranging meter, choose the 20 V DC range for battery and charging tests, because it’s the first range above 12 to 15 volts.

Step by step

Test 1: battery voltage (DC volts)

1. Make it safe. Ignition off, key out (or the keyless fob away from the car), and safety glasses on. Take off metal rings and watch bands.
2. Plug in the leads. Black into COM, red into V/Ω. Check the red lead is not in the A socket.
3. Select DC volts. Use the 20 V DC range on a manual meter.
4. Touch the probes to the battery posts. Red probe on the positive (+) post, black probe on the negative (−) post. Touch the posts themselves (or the clamp bolts), not just the plastic covers.
5. Read the display. A fully charged battery that has rested reads about 12.6 V. A minus sign just means the probes are swapped; it won’t hurt the meter. See the table below for what the numbers mean, and (see How do I test my car battery?) for the full battery test.

Test 2: charging voltage (engine running)

6. Keep hands, hair and leads clear of the drive belt and cooling fan, which can start on its own even with the engine idling.
7. Start the engine and measure across the battery again with the same setting. On most cars with a conventional charging system you’ll see roughly 13.5 to 14.8 V. Many newer cars have “smart” charging that can read lower at times, so a low reading alone doesn’t prove a fault. (see How do I know if my alternator needs replacing?)

Test 3: continuity (power off)

8. Remove the part or isolate the circuit. Pull the fuse, globe or switch out, or disconnect the battery (negative terminal off first). Continuity and resistance tests on a live circuit give false readings and can damage the meter.
9. Select continuity (the beep symbol) and touch the probes together. The meter should beep and show close to zero. This proves the meter and leads are working.
10. Probe each end of the part or wire. A beep and a reading near zero means there’s a continuous path. No beep and “OL” (open loop) means a break: a blown fuse, a broken wire or a failed globe filament. (see How do I check and replace a blown fuse?)

Test 4: resistance (power off)

11. Select Ω with the part disconnected from power, the same as for continuity.
12. Measure across the part (for example, a sensor or a motor winding) and compare the reading with the figure in the workshop manual. The meter adds a little resistance through its own leads: touch the probes together first and subtract that reading if you need accuracy.

Test 5: voltage drop while cranking (Medium)

A voltage drop test finds a corroded, loose or undersized cable or earth that a continuity test can miss, because it measures the cable while it’s carrying real current. You need a helper, and the battery should be charged (at least 12.4 V at rest).

13. Stop the engine from starting. Put the car in Park or neutral with the handbrake on. Disable the engine so it can crank but not start, as shown in the workshop manual (often by removing the fuel pump fuse or relay). If you’re not sure how to do this on your car, leave this test to an auto electrician.
14. Set the meter to DC volts. Leads in COM and V/Ω, as for a battery test. Use a low range (or let an auto-ranging meter choose), because you’re looking for fractions of a volt.
15. Positive side. Red probe on the battery positive post itself (not the clamp), black probe on the main terminal at the starter motor where the battery cable connects. Have your helper crank for no more than about 5 seconds while you read the meter.
16. Earth side. Red probe on the battery negative post, black probe on the starter motor body or engine block. Crank again and read the meter.
17. Compare the readings. A good cable reads close to zero. Example limits for a 12V car from Hella are about 0.5 V on the positive side (battery to starter terminal) and 0.3 V on the earth side (battery negative to starter body). Fluke suggests a healthy circuit is lower again, around 0.3 V positive and 0.2 V earth. Anything higher points to a corroded, loose or damaged cable or connection. Move one probe along the circuit, one connection at a time, to find where the voltage is being lost. Your workshop manual may give exact figures for your car.

Keep hands, hair and leads clear of the belt and fan while cranking, and refit the fuse or relay when you’ve finished. (see Is it my starter motor or my battery?)

Finishing up

18. Reconnect anything you disconnected. If you took the battery off, reconnect positive first and negative last.
19. Return the red lead to the V/Ω socket and switch the meter off. Leaving the lead in the A socket is the most common way to blow a meter’s fuse on the next voltage test.

What not to do

• Don’t put the probes across a battery with the red lead in the A (amps) socket. In that socket the meter is almost a dead short. Across a car battery it will at best blow the meter’s internal fuse and at worst burn the leads or meter and spark at the battery, which can give off hydrogen gas.
• Don’t measure current except in series. Amps are measured by breaking the circuit and putting the meter in line with it, never by touching across a voltage source. A battery drain test is the main reason to do this on a car, and it has its own procedure.
• Don’t crank or start the engine with the meter in series on the amps range. Starter current is hundreds of amps, far beyond a hand-held meter.
• Don’t use the ohms or continuity setting on a live circuit. Disconnect power first.
• Don’t probe airbag (SRS) wiring or connectors. SRS wiring is usually yellow. The current from a multimeter on the resistance setting can be enough to fire an airbag. This is professional-only work.
• Don’t test high-voltage parts on a hybrid or EV. Orange cables carry high voltage that can kill. A standard multimeter and leads are not rated for it.
• Don’t pierce wire insulation with the probe tips. It lets moisture in and causes corrosion later. Back-probe connectors from the wire side where you can, or use a proper back-probe pin.

Specs table

12V battery readings with a multimeter (DC volts)

Test	Reading	What it means
Engine off, rested overnight	12.6 V	About 100% charged
Engine off, rested overnight	12.4 V	About 75% charged
Engine off, rested overnight	12.2 V	About 50% charged: charge it
Engine off, rested overnight	12.0 V	About 25% charged
Engine off, rested overnight	11.9 V or less	Flat
Engine running, idle	About 13.5 to 14.8 V	Normal charging on a conventional system
Voltage drop while cranking, battery + to starter terminal	More than about 0.5 V	Positive cable or connection problem (Hella example limit)
Voltage drop while cranking, battery − to starter body	More than about 0.3 V	Earth cable or connection problem (Hella example limit)

Resting figures are RACV’s guide for a standard lead-acid battery. AGM batteries read slightly higher when full, and smart charging systems can show lower running voltages. Measure after the car has sat overnight, because a battery reads falsely high straight after driving or charging.

Continuity and resistance readings

Display	Meaning
Beep, close to 0 Ω	Continuous path: fuse, wire or switch contacts OK
No beep, “OL”	Open circuit: break, blown fuse, failed globe, open switch
Reading that changes when you wiggle the wire	Intermittent break or loose connection

What you’ll need

• digital multimeter (auto-ranging is easier for beginners)
• multimeter test leads with alligator clips
• back probe pin kit
• DC clamp meter (optional, for measuring current without breaking the circuit)
• multimeter replacement fuse (check the rating in your meter’s manual)
• safety glasses

When to call an auto electrician

• The readings don’t make sense, or a fault comes and goes.
• You need to measure current draw and you’re not confident wiring a meter in series.
• The fault is in airbag (SRS) wiring or any yellow connector. This is professional-only.
• The car is a hybrid or EV and the fault might involve the high-voltage system. This is professional-only.
• The battery or charging readings are outside the normal ranges and you’ve already charged and retested the battery.

Related questions

Q: What setting do I use to test a car battery with a multimeter? A: DC volts. On a manual-ranging meter, choose the 20 V DC range. Red probe on positive, black on negative. A fully charged, rested battery reads about 12.6 V. (see How do I test my car battery?)

Q: Why did my multimeter show 0 V or go dead when I tested the battery? A: The red lead was probably in the amps socket, which blows the meter’s internal fuse. Move the lead back to the V/Ω socket and replace the fuse with the rating shown in the meter’s manual.

Q: Can I check a fuse with a multimeter without taking it out? A: Yes, with the circuit powered: set DC volts and touch the black probe to a good earth, then the red probe to each test point on top of the fuse. Battery voltage on both sides means the fuse is good; voltage on only one side means it’s blown. (see How do I check and replace a blown fuse?)

Q: How do I find what’s draining my battery with a multimeter? A: You measure the current with the meter in series with the negative battery cable and pull fuses one at a time. It needs care to avoid blowing the meter.

Q: Do I need an expensive multimeter for car work? A: No. A basic digital meter with DC volts, ohms, continuity and a fused amps range handles most 12V jobs. Check that the current inputs are fused and the leads are in good condition.

Sources

1. RACV, “Car battery guide: how they work, when to replace them, and how to jump-start” – multimeter on the 20 V DC setting; red to positive, black to negative after the car has been off overnight; voltage vs state-of-charge guide (12.6 V 100%, 12.4 V 75%, 12.2 V 50%, 12 V 25%, 11.9 V 0%). https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
2. Fluke, “How to perform automotive continuity checks with a multimeter” – lead sockets and continuity setting; disconnect battery or isolate the circuit first; open circuit reads OL; don’t test powered circuits on continuity or resistance. https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-perform-automotive-continuity-checks-with-a-multimeter (checked October 2026)
3. Fluke, “11 automotive troubleshooting tests you can perform with a multimeter” – disconnect power before resistance or continuity tests; back-probe where possible; charging voltage typically 13.8–14.7 V under load. https://www.fluke.com/en/learn/blog/digital-multimeters/common-automotive-testing-with-a-multimeter (checked October 2026)
4. SparkFun, “How to use a multimeter: measuring current” – current must be measured in series; leaving the lead in the current socket and measuring voltage shorts the supply through the meter fuse. https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter/measuring-current (checked October 2026)
5. JS Alternators, “How to test your alternator: complete guide” – running voltage about 13.5–14.8 V on conventional systems; smart (computer-controlled) charging reads differently. https://js-alternators.com/blogs/blog/how-to-test-alternator (checked October 2026)
6. Battery University, “BU-903: How to measure state of charge” – lead-acid needs to rest before an open-circuit voltage reading; surface charge raises voltage after charging; AGM reads slightly higher than flooded. https://www.batteryuniversity.com/article/bu-903-how-to-measure-state-of-charge/ (checked October 2026)
7. Automotive Tech Info, “SRS diagnosis and repair” – don’t use an ohmmeter on airbag squibs (meter current can fire them); SRS harnesses are colour-coded yellow. https://automotivetechinfo.com/2011/11/srs-diagnosis-and-repair/ (checked October 2026)
8. Fluke, “How to check starter circuit voltage drop with a multimeter” – probe positions for the positive and earth sides; disable the engine so it can’t start; crank 4 to 5 seconds; about 0.3 V positive and 0.2 V earth. https://www.fluke.com/en-au/learn/blog/digital-multimeters/how-to-check-starter-circuit-voltage-drop-with-a-multimeter (checked October 2026)
9. HELLA Tech World, “Earth (31) – troubleshooting” – battery at least 12.4 V for testing; example maximum voltage drops for a 12V system (battery + to starter 0.5 V, to alternator 0.4 V; battery − to starter or alternator housing 0.3 V). https://www.hella.com/techworld/ae/ti/pdf/Earth-31-troubleshooting/Earth-31-troubleshooting.pdf (checked October 2026)

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

1. 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.
2. Never charge a frozen battery. In alpine areas, a battery that has frozen can explode when charged. Let it thaw and have it checked.
3. 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.
4. 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).
5. Switch the car off. Ignition off, key out, and lights, radio and other accessories off.
6. 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?)
7. Make sure the charger is unplugged and switched off at the wall.
8. Connect the red clamp to the positive (+) post.
9. 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.
10. Select the battery type (standard, AGM, lithium) and the charge rate if the charger asks.
11. Plug in and switch on. Check the charger shows it has started and the polarity is right.
12. 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.
13. 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.
14. Switch off and unplug the charger at the wall.
15. Remove the black clamp first, then the red.
16. 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.
17. 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.

Related questions

Q: Do I need to disconnect the battery to charge it? A: Usually not with a smart charger: charging in the car is fine if you follow the owner’s manual for where to connect. If you do disconnect it, take the negative terminal off first and put it back on last.

Q: Can I charge an AGM battery with a normal charger? A: Use a charger with an AGM mode or one the maker says suits AGM. The wrong charging profile can undercharge or overcharge an AGM battery and shorten its life.

Q: Can I leave a smart charger connected all the time? A: Most smart chargers drop to a maintenance mode when the battery is full and can stay connected, which suits cars that sit for weeks. Simple trickle chargers without this feature should be switched off when the battery is full.

Q: Is it safe to charge a car battery in the garage? A: Yes, if there’s good airflow and nothing nearby that sparks or burns. Charging lead-acid batteries gives off hydrogen, which can explode if it builds up.

Q: Will jump-starting my car charge the battery? A: No. A jump start only gets the engine going. A smart charger is the proper way to bring a flat battery back to full charge. (see How do I jump start a car safely?)

Sources

1. 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)
2. 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)
3. 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)
4. 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)
5. 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)
6. 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)
7. 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)
8. 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)
9. 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)
10. 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)
11. 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)
12. 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)
13. 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)