hi. Folks, can anyone help. Following heaps of advice about car battery charging I have been told that my car battery sitting at 12.3 -12.4 volts would be approximately 50% charged and with a 4 amp charger would take only 3-4 hours to fully charge. I have now done this and went to work yesterday with the comfort that the battery was 100%, and when I got home in the evening checked with a meter and found the battery was at 13.0 volts, so I was ecstatic. This morning I re-checked the voltage and found it was at 12.4, back to 50%, so am now confused. Have read up a lot about charging and the census of opinion is that the reserve capacity of which mine is 135, should be multiplied by .6 to give the amount of amp hours needed to charge (81) divided by 50 as 50% is missing, which gives 40.5, and thereafter a charge rate of 4 amps ( which my charger puts out) calculates to 10 hours of charging @ 4 amps (40.5/4). Should I therefore go & charge my battery which has 12.4 v for a further 10 hours to fully charge it?.
The fact it read 13.0 after a 20 mile trip down to 12.4 12 hours later is confusing me, is the charge from the alternator a false indication of a batteries charge ?, or do I maybe have a drain somewhere... Thanks for listening , John