Murphy BCEG-24-20 - Manual (Page 16)

Section 75 00-02-0615
02-29-08 - 12 -
Using Correct Size Battery Charger
The battery charger will need to provide both the standing load and minimum charge current.
If a charging current of 2 amps is required, and the standing load is 1 amp, then the charger
needs to be able to output a total of 3 amps.
Refer to genset manual for sizing of battery chargers to generator set. If installing your own
chargers, lead acid battery manufacturers recommend the following:
• Minimum charge current should be approximately 5% battery AH capacity.
• Maximum charge current to be equal to 25% battery AH capacity
NOTE: When batteries are normally charged by a charging alternator, a float
battery charger rated at lower than the minimum charge current is sufficient to
keep batteries in fully charged state.
Factors Contributing to Electrolyte Loss
• Physical damage to cells can cause electrolyte to leak or evaporate.
• High charging voltages will evaporate electrolyte.
Check charging voltage against battery type and voltage.
WARNING: If the batteries are being used at above 20
° Celsius, the chargers
output voltage should be temperature compensated at -3mV/
°F/Cell.
Battery Life
Two possible methods can be used for determining battery life:
• Using
Hydrometer
• Using a digital DC voltmeter
Follow these steps to check battery life.
1. Fully charge the batteries.
2. Disconnect batteries and leads and leave for 24 hours.
3. Measure either specific gravity (hydrometer) or terminal voltage (voltmeter) and
compare with the table on the following page.
4. If time is limited due to on-site testing, remove surface charge by either applying a 20
amp load for 3 minutes or crank engine for 10 seconds, then disconnect batteries and
leads and leave for minimum of 10 minutes.