Tesla Model 3 & Model Y 12V Battery
Reviewed by GarageDex editorial
A Tesla has two batteries: the big high-voltage pack that drives the car, and a small 12V auxiliary battery that runs the computers, lights, and locks. The 12V is the one that strands you when it dies - and it is NOT a standard group size, which is why you will not find a Model 3 or Model Y in a normal battery-size finder.
Why there's no group size
Battery-size finders match your car to a BCI group size (like 24F, 35, or 47) - a standard set of dimensions and terminals for lead-acid batteries in gas cars. Tesla designed its own 12V battery that does not follow that standard, so there is no group number to look up. That is deliberate, not a gap in our data - and it is why the Model 3 and Model Y appear in our wiper and filter finders but not the battery one.
2017-2020: lead-acid 12V
Early Model 3 (and pre-2021 Model S/X) use a small sealed lead-acid 12V battery, located in the frunk. It is replaceable, and because it is a weak point, many owners swap it for a longer-lasting lithium replacement. It still is not a BCI group size - buy the Tesla-specific unit.
2021+: lithium 12V
From 2021, Tesla switched the Model 3 and Model Y to a compact lithium-ion 12V (about 15.5 volts) auxiliary battery. It lasts far longer than the old lead-acid unit and is normally serviced by Tesla rather than swapped at home.
Signs the 12V is failing
A "12V battery needs service soon" alert, doors or screens acting up, or the car failing to wake are the classic symptoms. Because the 12V runs everything you touch, a dead one can lock you out even with a fully charged main pack.
Other Tesla parts
We do cover the standard maintenance parts that do follow normal fitment: Tesla wiper sizes and the cabin air filter.
Frequently asked
What battery group size is a Tesla Model 3 or Model Y?
None. Tesla uses a proprietary 12V auxiliary battery that does not follow the BCI group-size standard used by gas cars, so there is no group number like 24F or 47 to match. Replace it with the Tesla-specific part for your year.
Does a Tesla have a 12V battery?
Yes. Alongside the high-voltage drive pack, every Tesla has a small 12V auxiliary battery that powers the electronics, doors, and screens. When it fails the car may not wake up or unlock, even with a full charge in the main pack.
Can I replace a Tesla 12V battery myself?
On 2017-2020 Model 3 (and pre-2021 S/X) the 12V is a small sealed lead-acid battery in the frunk that experienced owners can replace. The 2021+ lithium 12V is integrated and is normally replaced by Tesla Service.
How long does a Tesla 12V battery last?
The older lead-acid 12V typically lasts 2-4 years. The newer lithium 12V (2021+) is rated for much longer - often the life of the car - though it can still fail early.
Need your car's exact spec? Find Tesla wiper & filter parts →