To maximize the life of your Rolls AGM battery, it is important that it is properly charged. As with all
lead-acid batteries, both over- and under-charging a Rolls AGM battery will result in shortened service
life. The best protection from improper charging is the use of a quality charger and routinely
checking that the charger current and voltage settings are maintained.
Please read the following instructions before using your battery.
The charger cabling should be insulated and free of breaks or cuts. The cable connectors should be
clean and properly mate with the battery terminals to ensure a snug connection. The charger’s AC
cord should be free of breaks or cuts and the wall plug should be clean.
- Fully charge batteries after each use.
- Charge in a ventilated area as gasses may be released through the pressure relief valve if the
batteries are excessively over-charged.
- Never charge a frozen battery.
- Ideal charging temperatures: 32°F – 104°F (0°C – 40°C).
NOTE: The ideal float voltage is the lowest voltage setting that will maintain the battery at full charge.
Rebulk Voltage: This setting determines the battery bank voltage may drop between a Float and Bulk charge. It may be set at personal preference. For assistance and recommendation, please refer to the charge controller manufacturer for instruction and detailed information on this setting.
The most important part of the charge cycle is the Absorption charge. The Bulk charge phase recharges the battery bank to an 80% level. The Absorption charge phase completes the charging cycle, during which charge resistance increases. Most chargers on the market have a timer that allows the user to adjust the duration for the required time to return the battery to full charge. To set the correct time, a simple calculation is used. With the help of the 20 AH capacity and charge current, you may calculate the remaining charge time required for the battery bank to reach 100% state of charge (SOC) using the following equation:
We recommend a charge current of 20% of the 20 hr rate for both Bulk & Absorption charge phases on AGM & GEL VRLA models.
[10% min, 20% recommended, 30% max]
t = 0.38 x (C/I)
t = Absorption Charge Time (Hours)
C = 20 hr Rated Capacity (AH) [ex: 2 strings x S6-460AGM models (415 AH) = 830 AH rated capacity]
I = Charging Current (Amps) [charger output min 10% up to max 30% of 20 hr rate]
2 strings of S6-460AGM batteries
20 hr rate = 415 AH x (2 strings) = 830 AH
I =20% of 830 AH = 166 Amps OR If charger is only 120 Amps max then 120 is used
T = 0.38 x 830/166 = 1.9 hrs OR T = 0.38 x 830/120 = 2.63 hrs