Freas HD99M Precision Hydrometer for 1.100 to 1.300 specific gravity readings on flooded deep cycle Lead-Acid batteries.
State
of Charge and Charging. This table is for the Surrette deep cycle batteries, but nearly all deep cycle batteries will be very close to these values.
The
truest measure of a battery's state of charge is the SPECIFIC GRAVITY
of the battery acid. The following shows the approximate state of charge
at various specific gravities at 77ºF / 25ºC.
| Charged |
Specific
Gravity |
| 100% |
1.265-1.275 |
| 75% |
1.225-1.235 |
| 50% |
1.190-1.200 |
| 25% |
1.155-1.165 |
| 0% |
1.120-1.130 |