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Fig. 3 Relationship between charging time and battery voltage,
temperature and internal gas pressure
Thermistor
Thermostat
Timer
Battery voltage
(Overcharge range)
Battery temperature
Charging time
Battery voltage, temperature and
internal gas pressure
5-3-2. Overcharge protection system
The Model UC 24YJ is equipped with a 4-way overcharge protection system ( , dT/dt, battery surface
temperature sensor and timer) to protect overcharging.
(1) Stops charging after full charging by means of both overcharge protection system and dT/dt overcharge
protection system:
As shown in Fig. 3, voltage and temperature of a battery increase suddenly near the end of charging.
The overcharge protection system detects such a sudden rate of change in the battery voltage and stops
charging just before the overcharge range (*). The dT/dt overcharge protection system detects a sudden rate
of change in the battery temperature and stops charging just before the overcharge range. Normally the
charging stop position by the overcharge protection system is almost the same as that by the dT/dt
overcharge protection system. However, when the battery is inactive due to extensive non-use periods or
near the end of the service life, the battery voltage does not change suddenly and charging may not be
stopped by the overcharge protection system. The Model UC 24YJ is equipped with the dT/dt overcharge
protection system as well as the overcharge protection system in order to prevent overcharge even in
such cases. The Model UC 24YJ always stops charging just before the overcharge range. Thus the charging/
discharging cycles of a battery is increased.
Charging/discharging cycles of a battery (ambient temperature 20˚C)
Ni-MH: about 500 cycles
Ni-Cd: about 1,000 cycles
Battery
internal gas
pressure
(*) In the overcharge range, the battery internal gas pressure rises rapidly due to generation of gas and it
causes high temperature, oxidation of atmosphere that promote degradation. If charging is continued in
such conditions, the safety valve will be activated and the electrolyte will be leaked from the battery.
Summary of Contents for UC 24YJ
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