Hybrids, EVs and 12V Batteries in Adelaide

This guide is for Adelaide drivers of hybrids, plug-in hybrids and fully electric cars who have been caught out by a car that simply won't switch on. It explains the small 12V battery these cars still rely on, why it goes flat, how to test and charge it safely, and which jobs belong with a licensed professional.

How can we help?

Need it fixed?

Get a quote from a local Hybrids, EVs and 12V Batteries in Adelaide auto electrician, for anything from a flat battery to a full fit-out.

Get a quote

Buying parts?

Quality auto electrical parts from Ozautoelectrics, an established Australian supplier since 2010, dispatched through a nationwide network. For retail and trade buyers.

Shop parts

Doing it yourself?

Free step-by-step guides written for South Australia conditions, with the parts you’ll need listed for each job.

Browse DIY guides

Auto electrician in Hybrids, EVs and 12V Batteries in Adelaide?

Are you an auto electrical business? List your business on this site.

List your business on this site

Your hybrid or EV still has a 12V battery

It surprises a lot of owners. A hybrid or electric car has a large high-voltage battery for driving, but it also has an ordinary-looking 12V battery. That small battery powers the computers, door locks, lights, infotainment and, most importantly, the relays that connect the big battery when you press the start button.

If the 12V battery is flat, the high-voltage system can't wake up. The traction battery might be nearly full, but the car will act as if it is dead. You press start and get nothing, or a flicker of dash lights and a string of warning messages.

Once the car is running, the 12V battery is usually charged by a DC-DC converter fed from the high-voltage battery, not by a belt-driven alternator. That converter only works while the car is switched on or, in many EVs, while it is plugged in and charging. When the car sits switched off, the 12V battery is on its own.

How Adelaide driving habits drain the 12V battery

Many Adelaide trips are short and suburban: a run from Glynde to the shops on The Parade at Norwood, a school drop-off in Morphett Vale, or a quick trip into the city from North Adelaide. Hybrids and EVs suit these trips well, but short drives give the 12V battery little time to recover from the load of waking the car's systems.

Other common culprits around Adelaide:

• Second cars that sit in the driveway for a week or more while the household uses the other car.
• Cars left in long-term parking at Adelaide Airport during an interstate or overseas trip.
• Owners who now work from home and drive only on weekends.
• Connected car apps that wake the car to check charge level or pre-condition the cabin.
• Dashcams, trackers or accessories wired to a permanent 12V feed.

Signs the 12V battery is on the way out

A tired 12V battery in a hybrid or EV rarely gives the slow cranking warning you get in a petrol car, because there is no starter motor to labour. Instead, watch for smaller clues.

Doors that don't respond to the remote, a car that takes longer to show READY, random warning lights that clear after a drive, or the infotainment system rebooting can all point to low 12V voltage. Many manufacturers fit the original 12V battery as a small AGM or lithium unit, and these can fail with little notice once they age. Our guide to what to do when a dashboard warning light comes on helps you sort urgent warnings from the rest.

Testing and charging it safely

You can test the 12V battery with a basic multimeter. With the car fully off and left to sleep for a few hours, a healthy 12V battery usually reads around 12.6 volts. A reading close to 12.0 volts means it is well discharged. See how to test a car battery for the full method.

To charge it, use a smart charger that suits the battery type. AGM batteries need an AGM setting, and lithium 12V batteries need a charger designed for them, so check the label before you connect anything. Many hybrids and EVs have jump points under the bonnet even when the battery itself sits in the boot or under a seat. The owner's manual shows where to connect.

Never touch or disconnect orange cables or anything marked high voltage. Those parts can carry a dangerous voltage even when the car is off.

Jump-starting a hybrid or EV

Most hybrids and EVs can be jump-started on their 12V system using a portable jump starter or another car, through the jump points the manufacturer provides. The jump only needs to wake the car's electronics, so it doesn't need much current. Once the car shows READY, the DC-DC converter takes over and starts charging the 12V battery.

Using a hybrid or EV to jump-start someone else's car is a different matter. Many manufacturers advise against it, because a starter motor can draw more current than the car's DC-DC converter and 12V system are designed to supply. Read your handbook first. Our guide on how to jump-start a car safely covers the general steps and connection order.

Replacing the 12V battery

When the 12V battery won't hold charge, replace it with the type and size the manufacturer specifies. Some hybrids keep the 12V battery in the boot or cabin, where it needs a sealed AGM battery, and sometimes a vent tube, so gas can't build up inside the car. Fitting a cheaper flooded battery in that location is not a good idea.

Some vehicles also need the new battery registered with a scan tool so the car's battery management charges it correctly. Before you disconnect anything, check whether you need your radio code or wheel alignment reset afterwards, and consider a memory saver. Our guide to car battery types explains the difference between flooded, AGM and lithium batteries.

Leave high-voltage work to licensed professionals

The 12V side of a hybrid or EV is ordinary auto electrical work. The high-voltage side is not. Faults with the traction battery, inverter, high-voltage cabling or onboard charger must be handled by a technician trained and equipped for high-voltage systems, with the right insulated tools and safety procedures.

The same goes for home wall chargers. Installing or altering fixed 240V wiring at your house is work for a licensed electrician, not a DIY job and not usually an auto electrician's job either.

Getting help around Adelaide

If your car won't wake up and a jump doesn't fix it, an auto electrician can test the 12V battery, check the DC-DC converter output and look for a parasitic drain from an accessory. Mobile auto electricians often come to the car, which helps if it is stuck in a home garage or a car park. Start with our pages for the Eastern Suburbs, Adelaide City and the Southern Suburbs.

Parts for this job

Order quality parts online from Ozautoelectrics, dispatched Australia-wide.

Get it done: get a quoteDo it yourself: shop smart battery chargers

Get it done: get a quoteDo it yourself: shop AGM batteries

Get it done: get a quoteDo it yourself: shop portable jump starters

Questions Adelaide drivers ask

Why won't my hybrid start when the main battery is charged?

The car needs its small 12V battery to wake the computers and close the relays that connect the high-voltage battery. If the 12V battery is flat, the car can't switch on, no matter how much charge the main battery holds. Charging or jump-starting the 12V battery through the manufacturer's jump points usually gets it going again, but a battery that keeps going flat needs testing.

Does an electric car's 12V battery charge itself while parked?

Usually only while the car is switched on, or in many EVs while it is plugged in and charging. Some EVs top up the 12V battery from the main battery while parked, but this varies between makes and models. If your EV sits for weeks, for example in airport parking, check the handbook and consider a 12V maintainer or a friend who can start the car.

Can I use my hybrid to jump-start another car?

Many manufacturers advise against it. A conventional starter motor can draw far more current than a hybrid's 12V system and DC-DC converter are designed to supply, and you risk damaging expensive electronics. Check your owner's manual. A portable jump starter is a safer way to help someone else, and it is handy to carry for your own car too.

How long does a hybrid's 12V battery last?

It varies a lot with how the car is used, the battery type and how often it sits unused. Cars that do short trips or sit for long periods tend to wear their 12V batteries faster. Rather than relying on age alone, test the battery with a multimeter or have it load-tested, and replace it with the type and size the manufacturer specifies.

Need an auto electrician in Adelaide?

Find local auto electricians and mobile services in the Adelaide directory, or start with your area: Eastern Suburbs, Adelaide City, Southern Suburbs, Western Beaches.

Run an auto electrical business in Hybrids, EVs and 12V Batteries in Adelaide?

• New to Ozautoelectrics? Apply for trade pricing on quality auto electrical parts.
• Already a trade customer? Log in and order parts at your trade price.
• Want more local customers? List your business on this site so drivers in Hybrids, EVs and 12V Batteries in Adelaide can find you.

Not confident doing this yourself?

There’s no shame in handing it over. A local auto electrician can diagnose the fault properly and get it done safely, especially for anything involving brakes, airbags, hybrid systems or air-con gas.

Get a quote from a local auto electrician Or shop the parts and do it yourself