Originally Posted by
Brendan
a faily easy way to test it under load is to turn on the ignition so it is in the "RUN" position ie as it would be when driving. then put a DVM accross the battery you should be detting about 13.2 volts with every thing turned off (there will be a small current draw ie pumps priming, ecu etc, then switch on say the rear heated screen, this draws quite a lot of current
! and see what the DVM now reads if it drops noticably then you have a old tired battery. if it doesn't you are fine!
hope this helps
That is not true, a car battery is 12V and will be 12.xxV, only with the engine running and charging will you see 13.xxV +!
But tbh this reading can be totally irrelevant, as it's when the battery is put under load will it shows it's signs, best way to do it, is as said take it to a shop they have a special tool they put across it which can simulate a load.
Essentially the voltage measurement just proves there is x amount of power there at the moment of time when tested.
Martin