Battery keeps going flat

Likely causes

1. Weak or dying battery55%

   A battery over 5 years old that rests below 12.4 V is very likely the culprit.

   Garage price: Car battery £115 – £245Fix it: Replace your car battery
2. Alternator not charging30%

   With the engine running, battery voltage should read 13.8 to 14.7 V. Below that, the alternator is not charging.

   Garage price: Alternator £255 – £640
3. Worn starter motor15%

   A single click on starting with a healthy battery points to the starter or its solenoid.

   Garage price: Starter motor £200 – £555

What you can check yourself

1. With the engine running, you should read 13.8 to 14.7 V at the terminals. If not, the alternator is not charging.

Fault codes often linked