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ICS1712

Controller Operation

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.

Soft Start Charge

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.

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

Figure 1: Graphical representation of average current levels during the four charging stages

Figure 2: High impedance voltage spike at the beginning of charge

Soft-Start

Fast Charge

Topping Charge

Maintenance Charge

Current

Time (not to scale)

(not to scale)

Stage 3

Stage 4

Stage 2

Stage 1

0

2 min

termination

termination + 2 hours

Average