Why EVs Still Have a 12V Battery

That old-school 12V battery powers a lot of stuff.

Closeup of a car 12V battery
Zeljko Radojko/Shutterstock.com

While electric cars have huge lithium-ion battery packs to turn the wheels, a regular 12V lead-acid battery handles everything else. At least for now.

Your fancy new electric vehicle or PHEV (plug-in hybrid electric vehicle) runs on massive lithium-ion battery packs and electric motors. However, if you look around, you’ll still find your typical 12V car battery or a lead-acid battery.

While EV battery technology continues to improve yearly, most all-electric cars still have a 12V battery like any gas-powered vehicle. This familiar battery is what the car uses to power all the accessories, including the radio and security system, among other things.

What Does the 12V Battery in an EV Do?

Battery warning light on dashboard
Bjoern Wylezich/Shutterstock.com

Electric cars have two main electrical systems that handle everything. The first is a powerful high-voltage system (400-800V) that makes your car move. Those lithium-ion battery cells deliver all the power to motors that crank out torque and spin the wheels.

The secondary system is just as important, and the low-voltage 12V battery powers almost everything else. That regular 12V car battery controls your vehicle’s ECU (electronic control unit) or the car’s brain. This system unlocks the doors with your phone or key fob, runs the stereo or infotainment display, dash gauges, alarm system, air conditioner, interior lights, and more.

The 12V battery controls most of the stuff on the inside, while the bigger battery system handles the outside. That’s an oversimplified explanation, as there’s more to it than that, but you get the gist of it.

Additionally, the 12V battery talks to the other high-voltage system with a power relay and is what “starts” your electric vehicle, in a sense. An EV doesn’t need cold cranking amps to turn over a gasoline engine, but it’s still required to allow the two systems to communicate and let the ECU get an electric car rolling. If the 12V battery dies, you can’t operate an EV.

When your vehicle isn’t in use or during an accident, the 12V system cuts off that dangerous high-voltage system for safety reasons. Basically, there’s a good reason EVs still have a regular car battery.

More importantly, the 12-volt system is affordable, reliable, and something all automakers understand well. Trying to redesign every aspect, convert those hugely powerful battery systems into a lower level for the stereo, and having to change everything isn’t very cost-efficient.

Does an EV Have An Alternator?

2022 Tesla Model 3

Now that you know an EV has a regular car battery, your next question is whether EVs have an alternator. Interestingly enough, most EVs do not have a traditional alternator.

An alternator takes the mechanical energy from your gas-powered engine as it rotates and turns it into electrical energy to recharge the 12V battery. As a result, it always has a charge and can start your car, unlock the doors, and has juice as long as you drive or start the engine with enough frequency.

That’s why the battery needs a jump when you let a car sit for too long. The alternator wasn’t able to keep it charged. Electric vehicles don’t have a motor, so there’s nothing to spin the alternator and charge a 12V battery.

Instead, many EVs use a DC-to-DC converter that sends power from the high-voltage system to the smaller 12V battery system when necessary. Then, that regular car battery is always charged up and ready to unlock your doors and do its job.

What Happens If the 12V Battery Dies?

12V car battery with jumper cables attached.

So, what happens if the 12V battery in an EV dies? Welp, the same thing that happens in a regular gasoline-powered car. Depending on how dead the battery is, you won’t be able to unlock the doors, use the radio, or drive the car. That’s because the power source for the brains of the operation doesn’t have any charge left.

Yes, you can quickly jump-start an EV like a regular car, but you’re not “jumping” the big lithium-ion packs. Instead, you’ll jump-start the little 12V battery that almost every car has under the hood or in the trunk.

However, it’s important to remember that you should only mess with the standard 12V battery. Furthermore, according to KBB, you shouldn’t use another electric vehicle (EV) to jump-start your EV’s 12-volt battery. Instead, find a regular gas car or use a portable jump starter.

It’s also worth mentioning that, if possible, make sure your EV is off and set to park before you start. And if you’re worried about anything or can’t locate the regular 12V battery, wait for an expert or roadside assistance.

Will Lithium-Ion Replace the Lead 12V?

Tesla logo on the hood of a vehicle. Justin Duino / Review Geek

While traditional 12V lead-acid batteries have powered vehicles for a long time, we’re starting to see a shift in the landscape. For example, newer Tesla Model S and Model X vehicles don’t have regular old battery systems. Instead, the company opted to use a new 12-volt lithium-ion auxiliary battery system.

And while a Li-ion 12V battery costs more to replace than the older style, they’re lighter, smaller, and last longer. We could see more auto manufacturers switch to this system or even a bigger 48V auxiliary battery. Why? Because they’ll run longer, they don’t need the cranking apps to turn over a gas engine, yet deliver more than enough juice to keep up with the growing demand for infotainment systems, self-driving, sensors, cameras, and more.

For now, most vehicles on the road, electric or not, still have a regular 12V lead-acid battery. However, don’t be surprised if that starts to change as electric vehicles continue to gain popularity.

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