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Electric Car Won’t Turn On? How a Dead 12V Battery Strands EVs
Why an EV with a charged main battery can look completely dead, the signs of a failing 12V battery, and how to jump-start an electric car safely.
By the ChargePatrol team · Updated · 2 min read
It surprises many new EV owners: the car has plenty of range, but the screen is black, the door handles will not present and the car will not shift. The culprit is usually the small 12V battery, not the big traction battery.
What does the 12V battery do in an EV?
It powers the computers, locks, lights and the contactors that connect the high-voltage battery. If the 12V battery is too weak, the car cannot “wake up” the main battery, so it behaves as if it is completely dead.
Common signs of a weak 12V battery
- A “12V battery low” or “service 12V battery” warning
- Slow or unresponsive touchscreen when you get in
- Doors or the charge port will not unlock
- The car will not enter Drive
- The car sat unused for a long time
Can you jump-start an electric car?
Usually yes, but the method matters. Most manufacturers provide 12V jump points under the hood or frunk, behind a panel or in the trunk. A portable jump pack connected to the correct points is the safest approach. Many manufacturers advise against using an EV to jump-start another car.
After the jump-start
Once the car wakes up, the high-voltage system normally recharges the 12V battery while the car is on. If it dies again soon, the 12V battery likely needs replacement; schedule service with your dealer or a qualified shop.
ChargePatrol offers EV jump-starts from $140 and a combined jump-start and charging visit for $185 when booked online.