Battery good or bad

[garrytheskate]

'84 LT25 petrol 1.9
Taken starter battery out of van and charged it up. When fully charged it showed 13.33v yesterday. Today it shows 12.90v. As it is still out of van so there is no drain on it, is the battery on the blink.
Thanks

[Mocki]

nope that is a fully charged battery .......

[CovKid]

Mind you, a battery can still be knackered even if it charges up ok. They eventually lose their stamina either through age or neglect and although they might charge up ok (even quickly), they can deplete just as rapidly making them useless for starting - or as a leisure. The only real way to know if its any good (at home anyway) is by using a meter across battery terminals when using starter motor. If it dips significantly below 10v briefly (like 9v), its probably gutless even if it recovers to 12.5v or more. In other words, the voltage is there but the amps have long since departed.

Short Winter journeys really take their toll on car batteries. They often seem to perform well in warmer months but soon show their true colours when its cold and a greater demand is placed on them.

[California Dreamin]

Just to answer the 13.3 volt to 12.9 volt drop over night....when a battery is 'initially taken off charge' they tend to hold on to a 'higher' voltage for a short time (first hour) but settle down to their realistic norm....12.9 volts is very good.

The real test is voltage drop under load (cranking or if you have a heavy discharge tester) I think the figure is something like 10.5 volts min after 10 seconds (its basically a great big resistor that loads the battery) This will give you a good idea of its stamina.

Martin