ICS1700A Datasheet, PDF (16/24 Pages) List of Unclassifed Manufacturers – QuickSaver Charge Controller for Nickel-Cadmium and Nickel-Metal Hydride Batteries

ICS1700A
Maximum Temperature Termination
Maximum temperature termination is best suited as a safety back-
up feature. Maximum temperature termination requires that the
thermal sensor be in intimate contact with the battery. A low
thermal impedance contact area is required for accurate
temperature sensing. The area and quality of the contact surface
between the sensor and the battery directly affects the accuracy of
temperature sensing. Thermally conductive adhesives may have to
be considered in some applications to ensure good thermal transfer
from the battery case to the sensor.
The thermal sensor should be placed on the largest surface of the
battery for the best accuracy. The size of the battery is also a
consideration when using temperature termination. The larger the
battery, lower the surface area to volume ratio. Because of this,
larger batteries are less capable in dissipating internal heat.
Additional considerations beyond the basics mentioned above may
be involved when using maximum temperature termination where
sudden changes in ambient temperature occur or where forced air
cooling is used. For these applications, the surface area of the
thermal sensor in contact with the battery compared to the surface
area of the thermal sensor in contact with the ambient air may be
significant. For example, bead type thermistors are relatively small
devices which have far less thermal capacity compared to most
batteries. Insulating the surface of the thermistor that is in contact
with the ambient air should help minimize heat loss by the
thermistor and maintain accuracy.
Charging System Status by Indicator
The Indicator Description List in Table 1 contains displays that are
caused by charging system abnormalities. At power-up or after a
reset is issued, one flash of the CMN indicator followed by a
continuous PFN indication results from a 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 a PFN fault 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
PFN fault indicator is active immediately after power-up or after a
reset is issued 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.
If the CMN and OTN indicators are active together, this is an
indication that the battery temperature has dropped to below 10°C
after a fast charge was initiated with the battery temperature
normal. If this condition is observed and the battery temperature
did not drop after fast charge was initiated, check the thermistor
circuit mechanically for poor contact and electrically for excessive
noise.
Enhanced Performance Characteristics
The ICS1700A is an enhanced performance, pin-for-pin re-
placement for the original ICS1700. Improved internal features
provide additional capabilities. The charge sequence, voltage slope
termination method, and analog-to-digital converter resolution
allow the ICS1700A to charge either NiMH or NiCd batteries. The
ICS1700A accepts either a thermal switch or thermistor input for
temperature sensing. The polling mode for battery detection
responds quickly to the removal of the battery throughout the
charge sequence. The reset input debounce eliminates sensitivity to
field effects and ground bounce when the PC board design
recommendations cited in this document are employed. The
temperature sense input debounce eliminates sensitivity to shock
and vibration associated with the use of a thermal switch.
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