What is an EV Traction Battery?
The huge high-voltage battery pack that actually powers the car.
Simplified animation — not to scale.
In plain English
The traction battery is the giant lithium-ion battery pack — usually mounted in the floor — that stores the energy used to drive an electric car. It typically runs at 400V or 800V (far higher than a normal car battery) and holds anywhere from about 40 kWh in a small EV to 100 kWh+ in a long-range one. It is by far the most expensive component in the vehicle.
"Think of it as a giant rechargeable phone battery the size of a mattress, bolted under the floor of the car. Look after the temperature and don't keep it at 100% or 0% all the time, and it'll last for many years."
How it works
The pack is built from thousands of small lithium-ion cells grouped into modules. A battery management system (BMS) monitors each cell's voltage and temperature, balances them, and protects against over-charge, over-discharge and overheating. Liquid coolant runs through the pack to keep it in its happy temperature window. When you accelerate, DC power flows out to the inverter; when you regen-brake or plug in, power flows back in.
Signs of trouble
- ⚠Sudden drop in real-world range
- ⚠"Reduced power" warning or limp mode
- ⚠Slow charging speeds even on a rapid charger
- ⚠State-of-charge jumping around erratically
- ⚠Battery warning light or amber traction-battery icon
£5,500 – £22,000
Always get a written quote. Prices vary by car, region, and parts brand.