ICS1708 Datasheet, PDF (3/16 Pages) List of Unclassifed Manufacturers – QuickSaver Charge Control IC for Nickel-Cadmium and Nickel-Metal Hydride Batteries

ICS1708
SoftStart Conditioning Charge
New, over-discharged, and batteries out of long term storage may exhibit an initial high impedance conditions in response to charging, as
shown in Figure 2. Unless dealt with, this high impedance condition can cause a voltage peak and -∆V condition at the beginning of the
charge cycle that can appear to be the response of an already full battery. To manage this condition, the ICS1708 applies a SoftStart
conditioning charge.
Figure 2: High impedance voltage spike at the beginning of charge
The SoftStart charge eases batteries into the fast charge stage by gradually increasing the duty cycle of the charge. The gradual increase
alleviates the voltage peak and the -∆V condition. The duty cycle of the applied current is increased to the fast charge rate, as shown in
Figure 3, by extending the current pulse on every cycle until the pulse is about 1.1 seconds in duration. The initial current pulse is
approximately 200ms. The CMN indicator is a continuous active low during the SoftStart conditioning stage.
Initial Pulse
Width
Initial Pulse
Width
increment
time
Initial Pulse
Width
2 x increment
time
cycle time
cycle time
cycle time
Figure 3: Cycle-to-cycle increase of the SoftStart current pulse widths
3