ICS1712M GALAXY [Galaxy Power, Inc.], ICS1712M Datasheet - Page 14

• Manufacturer Part Number: ICS1712M
• Description: Charge Controller for Nickel-Cadmium and Nickel-Metal Hydride Batteries
• Manufacturer: GALAXY [Galaxy Power, Inc.]

ICS1712
For example, a battery was monitored as it charged at a 1C rate in
25 C ambient. In the final minute of charge, the battery
temperature rose from 29.8 C to 31 C where full charge was
detected. With this data, the typical 10k
in the example above is checked to determine if its characteristics
satisfy the 4% decrease in resistance required for the last minute of
charge. The thermistor measures 8.37k
31 C. For a 1C charge rate, the resistance must decrease at least
4%/min. or more between 29.8 C and 31 C. The percent decrease
in resistance for the thermistor is calculated as:
This thermistor meets the 4%/min. requirement and will result in
termination at full charge at 31 C. The thermistor must be checked
for a 4%/min. decrease in resistance for the last minute of charge
near the hot and cold battery thresholds.
The battery in the example above was charged in a 25 C ambient
with its temperature rising 31 C - 25 C or 6 C. The temperature
rise was 31 C - 29.8 C or 1.2 C in the last minute before full
charge occurred. This information is used to check the thermistor
characteristics at the ambient extremes. If the selected 1C charge
rate is initiated at 12 C, the thermistor resistance change must
decrease 4%/min. between 16.8 C and 18 C. The thermistor
resistance at 16.8 C is 13.68k
resistance is 13.06k .
The thermistor meets the 4%/min. requirement and will result in
termination of fast charge at 18 C. If the selected 1C charge rate is
initiated at 37 C, the thermistor resistance change must decrease
4%/min. between 41.8 C and 43 C. The thermistor resistance at
41.8 C is 5.48k
The thermistor meets the 4%/min. requirement and will result in
termination of fast charge at 43 C.
13.68k
8.37k
5.48k
and at 43 C the thermistor resistance is 5.25k .
8.37k
13.68k
5.48k
- 8.01k
- 13.06k
-5.25k
(100)
(100)
(100)
and at 18 C the thermistor
@ 29.8 C and 8.01k
=4.30%
@ 25 C thermistor used
=4.19%
=4.53%
at
14
The 4%/min., 3%/min. and 2%/min. decrease in thermistor
resistance for the last minute of charge for the selected charge rate
are applicable for NTC thermistors other than 10k
provided that the following requirements are met:
A thermal switch that opens at about 45 C is recommended. The
thermal switch must be connected between the THERM pin and
ground. When the thermal switch is closed, the voltage at the
THERM pin must be below 0.5V for normal operation. When the
thermal switch opens (see Figure 12), the internal pull-up at the
THERM pin will raise the voltage above 4.2V and the ICS1712
will shut down and will not restart unless reset. Table 5 contains
the internal voltage thresholds used with a thermal switch.
Table 5: Thermal Switch Voltage Thresholds
Open Thermal Switch
Voltage
Closed Thermal Switch
Voltage
An external pull-up resistor to 5V is used to provide a
thermistor voltage of 1.67V @ 25 C.
The thermistor resistance at 25 C does not exceed 20k
that accuracy and adequate noise immunity are maintained.
The thermistor resistance increases by a factor of about 1.8
from 25 C to 10 C and the thermistor resistance decreases by
a factor of about 2.1 from 25 C to 45 C.
Using a thermal switch for hot battery detection:
Figure 12: Thermal switch to connection to
THERM pin
V
Parameter
DD
R = 75k
pu
ground at the THERM pin
normally closed thermal switch
opens at 45ºC
Voltage
>4.2
<0.5
Temperature
Battery
>45 C
<45 C
@ 25 C
so