Battery drain
Battery goes flat overnight or after a few days. Find parasitic draw or charging faults without guesswork.
MED RISK
Common symptoms
- Battery flat after sitting
- Slow crank
- Random electrical glitches
- Battery warning light sometimes
Cost expectations
DIY: £0–£60. Garage: £80–£200+.
Note: prices vary by car and region. Use this as a planning range.
Most likely causes (ranked)
- Parasitic draw — Module staying awake, aftermarket devices.
- Bad battery — Old or internally shorting.
- Charging issue — Alternator/regulator not charging properly.
- Door/boot switch — Lights stay on intermittently.
- Corroded terminals — Voltage drop mimics weak battery.
Quick checks (fast, low-cost)
- Fully charge battery then measure resting voltage next morning.
- Check charging voltage (engine running) ~13.8–14.6V (varies).
- Pull fuses one-by-one while measuring draw (advanced).
- Check for boot/glovebox lights staying on.
- Inspect terminals and ground straps for corrosion.
Recommended tools
These tools make diagnosis faster and stop you buying random parts.
Related fixes
If your symptoms don’t match perfectly, check these next.
What to do next
- Confirm battery health before chasing draws.
- If charging is low, fix alternator/regulator first.
- Remove aftermarket devices as a test.
AutoSolveHub helps you narrow possibilities. Always confirm critical repairs with proper testing and safe procedures.