User Manual

10
FLOODED LEAD-ACID BATTERY CHARGING
I
NITIAL CHARGE
Although all Rolls batteries are tested and charged prior to shipping, batteries will
self-discharge when stored and not in use. Upon installation, the initial charging
may take 10+ hours or more depending on the size of the battery bank and charge
current. Once the battery is fully charged, recheck the electrolyte level in the cell.
The fluid should be 6-12mm (1/4”-1/2”) below the vent tube on each cell as shown
in Figure 7. Carefully add distilled water to adjust as needed.
MULTI-PHASE CHARGING
The most common charge method for Flooded deep cycle batteries is a three-phase
charge cycle with periodic equalizations. Always be sure to follow the recommended
charging parameters as these will vary. Often, pre-programmed default settings are
not in line with the battery manufacturer's recommended voltage settings. Using these
may result in damage or battery failure which is not covered under the manufacturer
warranty. Refer to the charger manufacturer for specific programming instructions.
BULK CHARGE
The first of the three-phase charging process is the Bulk charge. During this stage the
maximum amount of current flows into the battery bank until a desired programmed
voltage is reached. For Flooded models, the recommended Bulk charge current is 10%
of the AH capacity of the battery bank, based on the 20 Hr AH rate (C/20) (min 5%, max
20%). Higher charge current may cause the battery bank to overheat or damage the
cells. A lower charge current may be used, however, this will prolong the required charge
time and increase the potential for sulfation build-up. Bulk charge voltage set points are
outlined in Table 2 (a & 2 (b Flooded Charging Parameters.
ABSORPTION CHARGE
The second and most important phase of the charge cycle is the Absorption charge.
Bulk charge typically charges the battery bank to approx. 80% SOC. Once reached, the
charger will then switch to the programmed Absorption voltage to complete the charging
cycle. Most three-phase chargers include an Absorption charge time setting allowing
the user to program the duration of time needed to reach a full state of charge (100%
SOC). To set the Absorption charge time, a calculation is done using the 20 Hr AH
rating of the battery bank (C/20) and the available charge current and/or max charger
output. As the battery bank nears 100% SOC, internal resistance in the battery
increases and charge current begins to decrease. It is assumed that over the time of the
Absorption charge that 50% of your maximum charge current will be available (factored
into the equation) 0.42 = (20%/50%) + 5%. 5% is added due to losses.