ICS1722
Soft Start Charge
Controller Operation
Some batteries may exhibit an unusual high impedance condition
while accepting the initial charging current, as shown in Figure 2.
Unless dealt with, this high impedance condition can cause a
voltage peak at the beginning of the charge cycle that would be
misinterpreted as a fully charged battery by the voltage termination
methods.
Charging Stages
The charging sequence consists of four stages. The application of
current is shown graphically in Figure 1. The soft start stage
gradually increases current levels up to the user selected fast
charge rate during the first two minutes. The soft start stage is
followed by the fast charge stage, which continues until
termination. After termination, a two hour C/10 topping charge is
applied. The topping charge is followed by a C/40 maintenance
charge.
The soft start charge eases batteries into the fast charge stage by
gradually increasing the current to the selected fast charge rate. The
gradual increase in current alleviates the voltage peak. During this
stage, only positive current pulses are applied to the battery. The
duty cycle of the applied current is increased to the selected fast
charge rate, as shown in Figure 3, by extending the current pulse
on every cycle until the pulse is about one second in duration. The
initial current pulse is approximately 200ms. The CMN indicator is
activated continuously during this stage
Average
Current
(not to scale)
Soft-Start
Stage 1
Fast Charge
Topping Charge
Maintenance Charge
Stage 2
termination
Stage 3
Stage 4
termination + 2 hours Time (not to scale)
0
2 min
Figure 1: Graphical representation of average current levels during the four charging stages
Figure 2: High impedance voltage spike at the beginning of charge
3
GALAXY [ GALAXY POWER, INC. ]
