Installation Manual

FLOODED LEAD ACID BATTERY CHARGING

MULTI-PHASE CHARGING

The most common type of charge method at present is a three phase charge

plus periodic equalizations. Check with your charger manufacturer for specific

programming instructions.

BULK CHARGE

The first phase of the charging process is the bulk charge. This is when the

maximum amount of current flows into the battery bank until a desired voltage

is reached. The recommended charge current is 10%-20% of the AH capacity

of the battery bank, based on the 20 Hr AH rate (C20). Higher current levels

may cause the battery bank to overheat. A lower current may be used; however,

this will prolong 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 most important part of the charge cycle is the Absorption charge. The Bulk

charge typically recharges the battery bank to approximately 80% state of

charge, the Absorption charge then completes the charging cycle. Most three

phase chargers include an Absorption time setting which allows the user to

program the duration of time needed to reach a full state of charge. To set the

Absorption time, a simple calculation is required. Using the 20 Hr AH rating of the

battery bank (C20) and the charger output, it is possible to determine the time

needed to fully charge the battery bank.

As stated previously, the Bulk charge phase brings the bank to approximately

80% state of charge. The remaining 20% charge is a function of time and current.

The charger will maintain current level until the Bulk set point has been reached.

The charger will then switch to the programmed Absorption voltage and timer. As the

battery charge nears completion, the 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 (this is factored

into the equation). 0.42 = (20%/50%) + 5%. 5% is added due to losses.

ABSORPTION CHARGE TIME

Where : T = 0.42 x C /I

T = ABSORPTION CHARGE TIME

C = 20 hr RATED CAPACITY (total battery bank)

I = Charging Current (Amps) (recommended 10% to 20% of C20 discharge rate)

0.42 = ( 20%/50%) + 5% (5% is added due to losses)