1. -Overheat condition
2. -Low temperature condition (below-49 F)
3. -Cell imbalance
4. -Open circuit
5. -Shorted circuit
If the battery charger finds a fault, it turns off and sends a fault signal to the Electrical Load Management System (ELMS). NiCd batteries are capable of performing to its rated capacity when the ambient temperature of the battery is in the range of approximately 60-90 F. An increase or decrease in temperature from this range results in reduced capacity. NiCd batteries have a ventilation system to control the temperature of the battery. A combination of high battery temperature (in excess of 160 F) and overcharging can lead to a condition called thermal runaway. The temperature of the battery has to be constantly monitored to ensure safe operation. Thermal runaway can result in a NiCd chemical fire and/or explosion of the NiCd battery under recharge by a constant voltage source and is due to cyclical, ever-increasing temperature and charging current. One or more shorted cells or an existing high temperature and low charge can produce the following cyclical sequence of events:
1. -Excessive current,
2. -Increased temperature,
3. -Decreased cell(s) resistance,
4. -Further increased current, and
5. -Further increased temperature.
This does not become a self-sustaining thermal-chemical action if the constant-voltage charging source is removed before the battery temperature is in excess of 160F.