"Jeff Morris" wrote in message ...
12.2 is rather high if the load is large. Also, different batteries have
different characteristics.

I use an Amp-Hour meter, but also watch the voltage. If my fridge is running -
a 30 Amp load - the Voltage can go to 11.9 even if the batteries are down only
25%. Anything lower than 11.8 is getting pretty low on most batteries.

The fully charged, no load Voltage is only of minor interest, since it isn't a
very reliable measure of anything. Once even a load is put on, it drop down to
about 12.6. If all you have is a Volt meter, its a bit difficult determining
what's really going on - too much depends the load and the recent history.


No load voltage is a good indicator, if you know how to use it. You
shouldn't read the voltage after charging without load and never with
a high load. With a small load (0.1 - 2 A, for 60 Ah) the no load
voltage is very constant and reliable. Fully charged will give 12,6x V
and 11.7 is very close to empty. You should not let this voltage drop
below 12 V, which is ~30% capacity. For reading the voltage you need
an accurate meter, since an error of 0.1 V is significant.

How can you accurately use an Ah-meter? How do you know what is the
starting point (after few hours loading capacity could be anywhere
between 70 and 100%)? How do you know how many Ah you battery can
really deliver? The real capasity depends on load and the rated
capasity is unlikely to be accurate.

Joakim