How to Diagnose and Test a Car Battery

(click for jump start advice)

Is The Battery Faulty?

Ideally you will have the battery tested with an electronic tester, but you can play detective, how old is the battery? (If over 6 years old I would replace) how can I tell how old it is? If it says look in the owner’s manual on the top it is the original factory fitted battery, some batteries have a recharge date on them and normally the battery would have been sold before this date.

If it has a built-in hydrometer, and it tells you it is fully charged (shows green) but it won't start the car we know one of the 6 cells has failed, as it only monitors one cell not all 6 (a good battery can't be flat and fully charged). If you have a volt meter connect to battery and observe the voltage when trying to start the car, if it reads 12 volts with no load but drops to a very low voltage when trying to start the battery is faulty. A good car battery that needed charging would read maybe 11.5 volts.

Click Links Below for More Help

1.Advice on Fitting Batteries

2.Jump Start Advice

3.Has the Battery got a Drain?

4.Alternator Charging System

5.Battery Flat can't get out of Park or Garage?

6. Car Battery Memory Savers (Radio Codes)