Stores electricity for use by the electric traction motor.Checked 2026-08-14
Hybrid traction battery
The high-voltage pack that drives a hybrid's electric motor, separate from the 12-volt battery that starts the car.
Also called: traction battery · hybrid battery · high-voltage battery · battery pack
What it means
Definition
The US Department of Energy's Alternative Fuels Data Center describes the traction battery pack in one line: it stores electricity for use by the electric traction motor. On a hybrid that is not plugged in, the same page says where that electricity comes from — the battery is charged through regenerative braking and by the internal combustion engine. It is a separate component from the 12-volt battery, which starts the engine and runs the lights.
Why a buyer cares
What it changes
It is the one component on a used hybrid whose condition is not visible and not inferable from mileage, and the answer comes from a scan of the pack rather than from the car's behaviour on a short drive.
In practice
Where you meet it
In the listing as 'hybrid', on the dash as a battery or hybrid-system warning, and on inspection reports as a hybrid battery health check.
Two things that look alike
Not the same as
The 12-volt battery is the one that goes flat and needs a jump; the traction battery is the high-voltage pack, and a hybrid has both.
Read next
Related terms
Where it shows up
Related problem files
Where this comes from
Sources
The battery is charged through regenerative braking and by the internal combustion engine.Checked 2026-08-14
Nothing citable was found on how fast a pack loses capacity, or on what a replacement involves, so the entry claims neither. The DOE page lists a thermal system that maintains a proper operating temperature range of the engine, electric motor and power electronics; it does not name the battery in that list, so the entry does not say the pack is cooled by it.