Which car? You cannot drop something like this without a source

I’m sure this is not what the poster meant, but in fact most EVs and hybrids use multiple battery technologies in parallel. For example, a Chevy Bolt has a lithium ion battery to power the drivetrain and a conventional lead-acid battery for the accessories. My old Prius had a NiMH battery for the drivetrain and a lead-acid battery for accessories.

> For example, a Chevy Bolt has a lithium ion battery to power the drivetrain and a conventional lead-acid battery for the accessories.

This seems like an odd choice - unless you already bought a supply of lead-acid batteries for the next 50 years or so.

I've read about a car using supercapacitors in the regenerative brakes to capture energy at high current and, then let it trickle back into the main batteries (or drivetrain) at levels that won't damage it.

This is a classic, it isn’t broken don’t fix it situation.

Many laptops had both a lithium ion battery and a watch battery used to keep the bios and an internal clock running after the battery died. https://www.makeuseof.com/tag/why-does-my-motherboard-have-a...

That was a bit of a necessity. Users wouldn’t want their clock to reset when they swapped batteries, and you couldn’t be sure the machine was connected to a time server to set the time at boot.

The 12v lane is ubiquitous, and standardized. Supercaps are inefficient when it comes to storage per weight and volume, discharge rate too.

Both lead acid and supercaps are not even remotely comparable to the main liion battery, they're suppliments, and not interesting ones

The supercaps aren't for long-term storage - just long enough to allow the extra juice to flow back to the batteries. Racing cars sometimes do that with flywheels.

As for 12V, all one needs is a regulator. Unless you have a long-term supply contract (that, I bet, won't be renewed for too long), a lead-acid battery is just dead weight.

It could be great if you were a car manufacturer that already had an existing, very large supply chain for lights, dashboard, powered window motors, and other accessories, that were already 12 volt.

But unless you have a already contracted lifetime supply of lead-acid batteries, a buck converter is much cheaper, and lighter.

Tesla switched from lead-acid to 12V lithium ion their S and X models in 2021. James May had some issues with his Tesla when the 12V battery went flat.

https://insideevs.com/news/546087/tesla-liion-12v-auxiliary-...

https://youtu.be/NsKwMryKqRE

Tesla is also switching to 48V for the accessories.

This was the best news I heard at Tesla investor day. It should simplify and cut the cost of the in-cabin wiring.

When Sandy Munro interviewed Elon Musk a couple of years ago he said "Why are you still using 12v stuff in the cabin?"

Musk's answer was that the automotive supply chain was entirely geared around 12v equipment and they had to take advantage of that to get to market quickly.

I'm glad those days are almost over.

Isn’t there a whole trucking supply chain geared around 24 Volts?

All it'd take is a middle terminal in a 24V battery to make it a 12/24V one.

That would run the risk of unbalanced batteries. I had a small truck years ago, and everything was 24V as far as I recall.

A lead acid battery is just a holdover from the way every car used to have one for the accessories, and unless you want to redesign all the accessories, it's easier to have a 12v-14v circuit just for that.

And before you say "oh, but they could just use a voltage converter from the high voltage battery", they need to consider that some accessories use hundreds of amps briefly (eg. the power steering - that makes for an expensive voltage converter), and the car still needs to operate lights and stuff while the high voltage battery is offline (eg. after an isolation fault).

For all of the above reasons, the lead acid battery is still there, even though a clean sheet design would never have one.

My Hyundai Ioniq hybrid has a 12v section of the Li-ion battery that can be charged off of the hybrid battery while the car is off with the press of a button so that the car never needs to be jump-started unless the entire hybrid battery is dead.

I don't think that is what this person is talking about. Yes having an extra lower voltage battery is totally normal and every EV either has a led acid or an additional smaller LiIon battery.

Having multiple chemistries in one battery pack is of course possible, but I don't any car who is actually doing that.

Can't find it on the fly.

I read about it a few month back but ev battery and types etc. Shows a lot of other topics.

Might have been Tesla when they announced the other cell type.