Schumacher DSR Automatic INC-14825A - Manual (Page 12)

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CALCULATING CHARGE TIME 10.
The Hydrometer or Electronic Method
To find the time needed to fully charge your battery, determine the
battery’s charge level with a hydrometer or electronic Percent-of-Charge
Tester. The following table will help you convert hydrometer readings to
percent of charge values.
SPECIFIC GRAVITY PERCENT OF CHARGE PERCENT OF CHARGE
NEEDED
1.265 100% 0%
1.225 75% 25%
1.155 25% 75%
1.120 0% 100%
When you know the percent of charge and the Amp Hour (AH) rating of
your battery, you can calculate the approximate time needed to bring your
battery to a full charge.
To convert Reserve Capacity to Amp Hours, divide Reserve Capacity by 2,
and add 16:
Example:
Amp Hour Rating = Reserve Capacity + 16
2
NOTE: The Reserve Capacity can be obtained from the battery
specification sheet or the owner’s manual.
To calculate the time needed for a charge:
Find the percent of charge needed. (A battery at 50 percent charge that 1.
will be charged to 100 percent needs another 50 percent (.50)).
Multiply the Amp Hour Rating by the charge needed (.50) and divide by
2.
the charger setting (17 amps average).
Multiply the results by 1.25 and you will have the total time needed, in
3.
hours, to bring the battery to full charge.
Add an additional hour for a deep-cycle battery.
4.
Example:
Amp Hour Rating x % of charge needed x 1.25 = hours of charge
Charger Setting
100 (AH Rating) x .50 (charge needed) x 1.25 = 3.676 hours
17 (Charger Setting)
100 x .50 x 1.25 = 3.676
17
You would need to charge your 100-Ampere Hour Battery for a little more
than 3 hours using the above example.