Lamar Technologies Alpha C-25 - Manual (Page 9)

3. OPERATING GUIDE
ALPHA C-25 Manual V2.1.doc Page 9
3.2.2 CONSTANT-POTENTIAL CHARGE METHOD
A charge source applies a fixed (constant) voltage (potential) to the battery. The
current supplied by the charge source fluctuates (rises and falls) with the battery
voltage.
There are several advantages of the constant-potential charge method. First, there
is less danger of gassing at an excessive rate. Secondly, batteries of the same
nominal voltage but with different capacities can be connected in parallel directly to
the charging source. Thirdly, batteries are charged more rapidly and with less
attention.
3.2.3 LEAD-ACID BATTERIES
With the constant-current charge method the voltage can climb to 34-37 volts.
Therefore, this method should normally not be used to charge lead-acid batteries,
especially not the sealed type VRLA (valve regulated lead acid). A preferred way is
to have the VRLA batteries constant-potential charged on automatic equipment at
a voltage of
28.5 +/ – 0.25 volts until the charge current stabilizes for 3 consecutive
hourly readings.
The constant-current charge method can however be used for reconditioning
VRLA’s. For conditioning VRLA batteries, first discharge 12 volt batteries to 9 volts
or 24 volt batteries to 18 volts, then recharge with CC (constant current) at the
C
1
/10 rate (one tenth of the C
1
rate or one hour capacity) for 16 hours. The battery
should be periodically monitored for overheating during reconditioning.
3.2.4 NICKEL-CADMIUM BATTERIES
Nickel-cadmium batteries may be initially charged with constant potential set to
14.5 (12 volt battery) or 28.6 (24 volt battery). After the initial charge the batteries
may be topped with a low constant-current (usually C
1
/10) charge.
The nickel-cadmium can also be completely charged in the constant-current mode.
Adjust the current to a lower rate for topping. A low constant current applied during
a long time can also be used to eliminate fading, previously called the “memory
effect”, from nickel-cadmium batteries.
3.3 PREPARATION FOR CHARGING
Before starting charging the battery, read the component maintenance manual
(CMM) or the Instructions for Continued Airworthiness (ICA) for the specific
battery. Ensure that the charge time and current or voltages from the battery
manufacturer are followed.