Car wont jump start

forgotmyname

No your calculations are totally flawed. Yes the voltage will drop after being disconnected from a charger.

The charger puts out a higher voltage than the batteries normal voltage, You get get 13+ volts right after charging because the battery is warm. Let it cool for a few hours and it will drop to around 12.6 to 12.8.

If it drops below 12.4 with no load then its weak. Put your headlights on with the engine off and the voltage should still be above 12.2.

Joe_Horner

Nice explanation, forgotmyname, and may well save the OP buying a battery he may not need yet.

Sometimes I do think some of the other posters here must be employed by Exide

forgotmyname

Shhh im employed by CCBC (Cheap Chinese Battery Company)


All our batteries have small circuit boards to fake the test results, And appear all good even when dead



Apologies if there is a real company with that name But you may want to consider changing it....