ICS1722
The voltage slope termination method used by the ICS1722
requires a nearly constant current flow into the battery during fast
charge. Charging the battery in equipment that draws a known
constant current while the battery is charging should have this
current draw added to the fast charge current. Using the ICS1722
for charging the batteries in equipment that randomly or
periodically requires moderate current from the battery during fast
charge needs evaluation. Equipment that randomly or periodically
requires high current from the battery during fast charge may cause
a voltage inflection that results in termination before full charge. A
voltage inflection can occur due to the charge current decreasing or
fluctuating as the load changes rather than by the battery reaching
full charge. The voltage slope method will terminate charge based
on voltage inflections that are characteristic of a fully charged
battery. The
Charging System Status by Indicator
The Indicator Description List in Table 2 contains displays that are
caused by charging system abnormalities. When the CMN
indicator is flashing with no other indicator active, there is voltage
present at the battery terminals with the current source off and no
battery. Check the current source and ensure that it produces no
more than the equivalent of 350mV/cell when turned off with no
battery. If the VIN divider resistors were not properly selected, an
open circuit voltage that is actually less than the equivalent of
350mV/cell with the charger off and no battery will not divide
down this open circuit voltage properly and produce the CMN
flash indication. Check the VIN divider and ensure that it properly
normalizes the battery voltage to the electrochemical potential of
about 1.2V cell. If the CMN flash indication occurs with the
battery installed, then the constant current source is producing
more than the equivalent of 350mV/cell when off and there is an
open connection between the charger terminals and the battery.
Check wires, connections, battery terminals, and the battery itself
for an open circuit condition.
ICS1702 and ICS1712 charge controllers have temperature
termination methods for equipment that randomly or periodically
draws significant current from the battery during fast charge.
Charging sources that produce decreasing current as fast charge
progresses may also cause a voltage inflection that may result in
termination before full charge. For example, if the charge current is
supplied through a resistor or if the charging source is a constant
current type that has insufficient input voltage, the current will
decrease and may cause a termination before full charge. Other
current source abnormalities that may cause a voltage inflection
that is characteristic of a fully charged battery are inadequate ripple
and noise attenuation capability or charge current decreasing due to
thermal drift. Charging sources that have any of the above
characteristics need evaluation to access their suitability for the
application if the use of the voltage slope termination is desired.
If the MMN and CMN indicators are alternately flashing, the likely
cause is no battery with the ICS1722 programmed in the
discharge-to-charge auxiliary mode. If the battery is present, check
wires, connectors, battery terminals, and the battery itself for an
open circuit condition.
If the MMN indicator is active at the initiation of fast charge, check
the external pull-down resistor from OPREF to ground. A voltage
at OPREF that exceeds 2.3V will prevent the start of fast charge.
The controller soft start stage, built-in noise filtering, and fast
charge timer operate optimally when the constant current source
charges the battery at the rate selected. If the actual charge current
is significantly less than the rate selected, the conditioning effect of
the soft start stage and the controller noise immunity are lessened.
Also, the fast charge timer may cause termination based on time
duration rather than by the battery reaching full charge due to
inadequate charge current.
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GALAXY [ GALAXY POWER, INC. ]
