These instructions apply to the Tesla Model S (2012-2021).
For other models, please choose your vehicle here.
Like any car, a Tesla Model S (2012–2021) has a small 12 V battery that powers the locks, screens and the frunk release — separate from the large high-voltage drive battery. When the 12 V fails, the car may not wake and the frunk can stay shut, so there is a specific way to get in and swap it.
On pre-2021 cars the 12 V battery sits in the frunk (front trunk), under the liner near the firewall. On the 2021 refresh it moved under the rear seat.
How to open the frunk when the 12 V battery is dead
- At the front bumper, pull off the small cover that also hides the tow-eye point.
- Behind it you will find two wires — one red (positive) and one black (ground).
- Touch a portable 12 V source to them, matching polarity: red to +, black to −. A jump pack is ideal, though even a small 9 V battery is usually enough to trip the latch.
- The frunk releases with an audible pop — lift it to reach the 12 V battery (pre-2021 cars).
How to replace the Model S 12 V battery
- If the car still has any power, switch it off from the touchscreen (Controls > Safety & Power off / Power Off) and wait a couple of minutes.
- Remove the frunk trim/cover to expose the battery (pre-2021), or lift the rear seat base on the 2021 refresh.
- Disconnect the negative (−) terminal first, then the positive (+), and remove the hold-down bracket.
- Fit the replacement — a Group 51R AGM (or the correct lithium 12 V where fitted) — reconnect positive first, then negative, and refit the bracket and trim.
Safety: only work on the small 12 V battery and its black/red wiring. Never touch the thick orange high-voltage cables or the main battery — those are not an owner job.
Frequently asked questions
Where is the 12 V battery on a Tesla Model S?
In the frunk under the liner on 2012–2020 cars; under the rear seat on the 2021 refresh. It is the small 12 V battery, not the high-voltage pack.
My Model S is dead and the frunk won’t open — what do I do?
Apply external 12 V to the red and black wires behind the front tow-hook cover to pop the frunk, then replace the battery.
How long does a Tesla 12 V battery last?
The lead-acid units often need replacing every few years; later cars use a longer-life lithium 12 V. A warning on the screen or erratic electrics is the usual sign it’s failing.
If a 12 V or electrical warning stays on after the swap, you can look up the fault code on autodtcs.com.
Independent guide — not affiliated with Tesla. Always follow your official service manual and safety precautions. Read our full disclaimer.