A NiCD (nicad) charger can be a simple voltage supply and a power resistor as Thunderchild mentions.
But there are things to consider:
NiCD (and NiMH for that matter) is most happy to be charged in about 1 hour. If the battery to be charged is rated 2000mAh, then the charger should output 2000mA of charging current.
The charge termination (when to stop charging) is a very important matter to consider. This can be done in several ways:
- The user terminates the charge by removing the battery either after the 1 hour charge period or when the battery becomes warm to the touch.
- A timer terminates the charge after 1 hour.
- A temperature sensor terminates charge when the battery temperature is around 40˚C.
- A deltaV peak detector terminates charge (when a NiXX battery is fully charged, then voltage drops 10-20mv per cell, this can be detected and used to stop the charging).
- A deltaT detector terminates charge (the battery temperature rises when the battery is fully charged and when the temperature rises 1-2˚C per minute, the charge should be terminated).
Some usefull links on battery charging:
http://www.batteryuniversity.com/
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Proper battery charging is not easily archieved :roll:
I hope this helps :wink:
Regards,
Futterama