Judy
Below is the battery voltage vs depth of discharge info:
Your voltage readings indicate an almost completely discharged battery (gel
cell 90% discharge is 11.22 volts at 77 degrees F). When you check the
voltage of a battery after a charge, you should let the battery sit for a
few hours and better yet, put a small load on the battery while you check
the "full charge" voltage. Otherwise, you may be reading an artificially
high surface charge. A digital voltmeter will give you a better picture,
however, I suspect that the battery in question has gone belly up and will
need replacement if you expect to run any significant loads. Remember, if
you want to get a reasonable life from the battery, you should not discharge
it much below 50% of capacity - and recharge it as soon as possible.
>From the Battery FAQ at www.windsun.com
On the table below, you have to be careful that you are not just measuring
the surface charge. To properly check the voltages, the battery should sit
at rest for a few hours, or you should put a small load on it, such as a
small automotive bulb, for a few minutes. The voltages below apply to ALL
Lead-Acid batteries, except gelled. For gel cells, subtract .2 volts. Note
that the voltages when actually charging will be quite different, so do not
use these numbers for a battery that is under charge.
Voltage at DOD
Here are some no load typical voltages vs depth of discharge.
(figured at 80% max discharge and 77 degrees F)
1% = 12.91 Volts.
10% = 12.8
20% = 12.66
30% = 12.52
40% = 12.38
50% = 12.22
60% = 12.06
70% = 11.90
80% = 11.70
90% = 11.42
100% = 10.50.
Regards
Jobst