Xantrex Technology Link 1000 - Manual (Page 51)

Charging Functions
43
To test battery capacity:
1. Charge the battery until the charged parameters are met.
This resets Ah to zero.
2. Turn on a load that draws approximately 5% of the
expected battery capacity.
3. Check the current by looking at the Amps display. The
load should be constant (for example, a light bulb).
4. Put the Link 1000 in Volts display mode.
5. When the voltage drops to 10.5 volts (or 21 volts if you
are testing a 24 volt system), turn the load off. (It should
take about twenty hours for the voltage to drop.)
6. Look at the Ah display. The number of Ah displayed
is the actual battery capacity.
If less than twenty hours passed before the voltage fell to
10.5, you can still determine the capacity by completing a
simple calculation. For example, assume that you have a 12
volt battery rated at 100 Ah. Apply a 5 amp load. If it only
took ten hours for the voltage to reach 10.5, the Link 1000
would display
–50Ah. This number is the 10 hour capacity.
By dividing 50 by 89% (see the preceding table), you
determine that the actual 20 hour capacity is 56 Ah. You
could repeat the test at 5% of the tested capacity (2.8 amps) to
verify the actual capacity.
10 89%
5 78%
3 66%
1 45%
Battery Capacity at Various Discharge Rates
Hours to Discharge
Capacity (as a percent of the
20 hour rate)