The red battery light usually means the car is not charging its battery, not that the battery is flat. Causes and what to do.
Looking for more detail? Our full guide covers this topic in depth, with step-by-step advice and sources.
The charging system is not keeping the battery charged while the engine runs.
What it looks like
A battery with + and − symbols. Colour: Red.
Common causes
- Failed alternator
- Broken or slipping auxiliary (alternator) belt
- Loose or corroded battery terminals
- Wiring faults
What to do
- Switch off non-essential electrics (heated seats, rear screen heater, stereo).
- Drive to a safe place or garage nearby without switching off, because the car may not restart.
- If the belt has snapped, it may also drive the water pump or power steering, so stop and call for help.
Can I keep driving?
Only a short distance to safety.
MOT
Not an MOT item, but the battery must be secure and terminals sound.
Symbols vary slightly between makes. Always check your owner's handbook. General guidance only; if in doubt, call your breakdown provider.
Sources and further reading
Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.