If your hybrid won't power on, the small 12-volt battery is the usual cause, not the expensive high-voltage pack. We come to the car, test the 12-volt and the car's charging of it, and replace it on the spot. These are often AGM batteries tucked in the trunk or under a seat, and we handle the trim and the vent tube. We don't work on the high-voltage battery.
Two batteries in one car
The big battery drives the car. It's under the back seat or the floor, it's expensive, and it isn't our job.
The 12-volt battery is small and ordinary. It wakes the car up. When you press the power button, the 12-volt boots the computers and closes the relays that connect the big battery. If it's weak, the car never gets that far. You get a dim dash, a wall of warning lights, a key fob that won't unlock the doors, or just nothing.
Why they fail
Hybrid 12-volt batteries don't crank an engine, so they tend to be smaller with less reserve. Hybrids also stay partly awake when they're parked, for connectivity, updates and alarms. And if the battery sits in the trunk of a car parked at the airport in July, it's baking. Put those together and they quit with little warning. Hybrid 12-volt batteries explains more.
What the job involves
- Confirm it's the 12-volt with a test.
- Memory saver on, where it makes sense.
- Pull trim panels to reach it if it's in the trunk or under a seat.
- Swap the battery and reconnect the vent tube if there is one.
- Power the car up to Ready.
- Check that the car's DC-DC converter is charging the new 12-volt.
Some cars want a window or clock reset after. We'll tell you.
Jumping a hybrid
Most hybrids can be jump-started at designated terminals under the hood, following the owner's manual. Many should not be used to jump someone else's car. If you're unsure, call us.
EVs
EVs have a low-voltage battery too, and when it's weak, an EV can refuse to power on just like a hybrid. Some EVs use unusual battery types or procedures. Tell us the year, make and model and we'll tell you honestly whether it's something we can do on site.
Where we see the most hybrids
Dunedin, Safety Harbor, Seminole Heights, New Tampa near USF, and the Trinity area. But we go everywhere in our service area.
Questions we get about this
Is my hybrid battery dead?
Probably not the big one. If the car won’t power on at all, the 12-volt battery is the most common reason.
Do you work on the high-voltage battery?
No. We replace the 12-volt auxiliary battery only.