DCW20
User Manual rev. 5
Page 9/34
3.1.3 Battery charger
The battery charger supports
various chemistries
such Lead-Acid, Nickel, Lithium and
Supercapacitors. The charging algorithm for each chemistry is given below. Other charging algorithms
can be implemented by request (contact factory).
The battery charger automatically reduces the current to avoid exceeding the maximum input current
(§4.2.21) in case of high current load.
The user must set the following parameters to allow the charger to perform correctly:
Battery type (§4.2.5).
Battery charge voltage (§4.2.6)
Battery charge current (§4.2.7)
Battery float voltage (§4.2.8)
The battery charge terminates in case at least one of the following conditions are satisfied:
Low current:
The measured battery charge
current is lower than 10% of the “
Battery
charge current
” while the measured voltage is at least 98% of the “
Battery charge voltage
”
.
Timer:
the charge is terminated after the battery has been charged for a predetermined
amount of time. The value is automatically calculated by the device.
For Nickel batteries only, the following conditions are also checked:
Temperature Cutoff (TCO):
The batter
y temperature if higher than the “Battery maximal
temperature” (§4.2.14) minus 3°C for more than one minute. For example, if the maximal
battery temperature is set to 60°C, the charge terminates in case the temperature is higher
than 57°C.
Rate of Temperature Increase (
ΔT/dt):
The battery temperature is rising at a rate equal or
superior to 1°C/min. To avoid unattended end of charge do not place the system on an
ambient with rapid changes of temperature (for example exposed to direct sunlight).
The charger voltage is independent on the input voltage (power supply), and is user settable.
Lead acid and lithium batteries share the same 3 stages charging algorithm as shown on Figure 5.
Time
Current
Voltage
Constant current
Constant voltage
Maintenance
Charge current
Charge voltage
Float voltage
Figure 5: Lead acid and Lithium charging algorithm
For nickel batteries, during maintenance, the DCW20 gives pulses of 3s every 30s with a maximum
current of 1/10 of “
Battery charge current
” and maximum voltage equal to “
Battery charge voltage
”.
DCW20_040-02-700-005-EH-1117