Regal 53 SC Owner's Manual page 67

Systems
BATTERY TESTING
For all battery testing you must fi rst fully charge the battery
and then remove the surface charge. This could be done
by discharging the fully charged battery for several minutes
by activating an object that draws heavily from this battery.
If a digital volt meter is used to check an AGM battery
expect readings in the 12.8 to 12.9 range. Readings in the
AGM battery around the 10.5 range typically indicate a
shorted cell.
If a load meter is used to test a AGM battery, the actual
draw typically needs to be 1/2 of the CCA rating. Before
load testing the battery needs to be fully charged.
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