User Manual

– 25 –
Temperature Compensation
As the temperature rises, electrochemical activity in a battery
increases and conversely decreases as temperature falls.
Therefore, as the temperature rises, the charging voltage
should be reduced to prevent overcharge and increased,
as the temperature falls, to avoid undercharge. In
general, in order to attain optimum service life, the use of
a temperature compensated charger is recommended. The
recommended compensation factor for NP batteries is
-3mV/°C/Cell (for float/standby) and -4mV/°C/Cell. (cyclic
use). The standard centre point for temperature
compensation is 20°C. Figure 29 shows the relationship
between temperatures and charging voltages in both
cyclic and float/standby applications.
In practice where there are short term temperature
fluctuations between 5°C and 40°C, temperature
compensation is not absolutely essential. However, it is
desirable to set the voltage at a value shown in Figure 29
which, as closely as possible, corresponds to the average
ambient temperature of the battery during its service life.
When designing a charger equipped with temperature
compensation, the temperature sensor must sense only
the temperature of the battery. Therefore, consideration
should be given to thermally isolating the battery and
temperature sensor from other heat generating
components in the system.
CYCLE USE
STAND-BY USE