12V batteries fail in all cars, or is it just me?

Not trying to downplay the hassle, and I get that some EV issues are unique…

But it hit me that every car I’ve ever owned has had a 12V battery fail on me, often more than once. I’ve lost count of how many trips I’ve made to return dead batteries for a replacement. Waking up to a dead car battery was the worst, especially before jump packs existed – it was either call for help or dig up jumper cables and hope a neighbor was around.

Funny enough, I haven’t had this issue with my EV6 yet. In fact, I’ve used my jumpstart pack a couple times, but only to help out others with ICE cars.

Anyway, no hate on anyone dealing with this – except maybe at 12V battery tech. Is there really no better option out there?

What bothers me is with ICE cars, the 12V usually fails when you’re starting the car, which is annoying but not dangerous. But with the EV6, it can fail while you’re already driving. You get this “pull over now” message, which is pretty scary and can leave you stranded.

@Jason
Yeah, I feel that. If your alternator goes in an ICE car, you’re stuck too. Happened to me during a snowstorm in Truckee – not fun.

A lot of people hit the three-year mark where cheap 12V batteries start dying. When that happens, it’s worth investing in a better one, and you’ll get more life out of it.

Howard said:
A lot of people hit the three-year mark where cheap 12V batteries start dying. When that happens, it’s worth investing in a better one, and you’ll get more life out of it.

With the relatively light duty a 12V battery has in an EV (compared to starting an ICE car), shouldn’t we expect them to last longer? Honest question here – I’m no battery expert.

@olivia
I thought so too. I tailgate a lot, so I keep the car off with the hatch open, sometimes with the radio on, and my 12V still died at about 2.5 years. I replaced it with a better battery, and now I just leave the car on or in accessory mode. I wonder if it’s a Kia battery issue or just bad luck with these 12Vs?

@Howard
Here’s a guess from someone who’s just thinking out loud. EV 12V batteries may not last as long because the car lets them discharge a lot before recharging, unlike ICE cars where they’re constantly topped off while running.

If that’s the case, AGM batteries might do better in EVs since they handle sitting in a partially charged state better than regular lead-acid ones.

@olivia

tolerant of sitting in a partially discharged state

No lead-acid battery chemistry really is. LFP could be the solution here, or we just proactively replace them every 2-3 years instead of waiting for a failure.

It’s frustrating across brands. Even my Porsche Cayman came with a factory battery that died in just a few years. I’ve started budgeting for a better battery as part of any car I get. Put an AGM battery in my EV6, and so far, I haven’t seen a 12V failure warning since.

@Imani
Do AGM batteries handle deep discharges better than regular lead-acid batteries?

Yeah, 12V failures shouldn’t be this common. These batteries should last at least a few years unless you’re in a super hot climate.

Kenneth said:
Yeah, 12V failures shouldn’t be this common. These batteries should last at least a few years unless you’re in a super hot climate.

Totally agree. A $50k car should have a quality AGM battery, not whatever budget option they used. I swapped mine for a better one, and even in Texas, I expect it to last 3-5 years. In my 2010 ICE car, I went through 3-4 batteries over its lifetime too, so it feels like a normal part of maintenance now.

It bums me out they can’t just run the whole car off the high-voltage battery with a converter. Seems like it’d make things simpler.

jeff said:
It bums me out they can’t just run the whole car off the high-voltage battery with a converter. Seems like it’d make things simpler.

I’ve read that this would complicate things due to all the peripherals. So the 12V basically acts as a bridge. I agree, though – they could come up with something better than a 12V you get off the shelf at AutoZone.

@Maria
If the battery is just a consumable, it’s actually nice that we can buy replacements anywhere and pick the quality we want.

jeff said:
It bums me out they can’t just run the whole car off the high-voltage battery with a converter. Seems like it’d make things simpler.

Right? Feels outdated that an EV even needs a 12V battery – like a leftover ICE design element.

@Randy
The alternative would be an 800V battery always connected, which is dangerous. You’d also need a heavy-duty contactor, which isn’t practical to run manually. You need some power source to connect and disconnect the high-voltage battery safely.

There could be other auxiliary power options, but sticking with a 12V lead-acid battery is probably the safest option.

@Randy
The 12V is necessary to engage the main battery when you start the car.

jeff said:
It bums me out they can’t just run the whole car off the high-voltage battery with a converter. Seems like it’d make things simpler.

They actually do rely on the high-voltage battery when it’s engaged. The car has a DC-DC converter that powers everything once the car’s on, similar to an alternator in an ICE vehicle. The 12V just kicks things off by activating the main battery, which is part of the startup sound you hear.

jeff said:
It bums me out they can’t just run the whole car off the high-voltage battery with a converter. Seems like it’d make things simpler.

That’s one thing I find interesting about the Cybertruck – no 12V battery. It’s all run on 48V. I don’t fully understand it, but I think it just keeps a single cell connected to run basic functions. Supposedly simplifies the wiring, too.