Batteries rarely die without notice. The slow crank on a cold morning, the headlights that look a little dim, the clock that keeps resetting — these are the quiet hints before the silent click of a battery that's finally given up. In the UK it's almost always the first proper cold snap that finishes the job.
The warning signs
- Engine cranks slowly or hesitates before starting, especially when cold
- Headlights dim noticeably at idle, brighter when you rev
- Electrical glitches — flickering lights, a resetting clock, stop-start that stops working
- A battery warning light on the dashboard
- A battery more than four to five years old
Battery vs alternator
Two different culprits get blamed for the same symptom. The battery starts the car; the alternator charges it while you drive and runs everything once the engine is on. If a freshly charged battery keeps going flat, the alternator is the likely suspect — it's no longer doing its job.