This following circuit diagram is a diagram to make a simple solar cell NiCad charger. The charger is using max 639 and solar panel. Many electronic devices such as the camera or mobile phones use this kind of battery as their power supply. This circuit can be used as a charger for those devices.
R1 = 820K, 1%
R2,R3 = 75K, 1%
R4 = 1M, 5%
D1,D2 = 1N5817, Schottky diode, or NTE585
L1 = 100uH, coil
U1 = MAX639, integrated circuit
C1 = 100uF/40V, Electrolytic capacitor
C2 = 47uF/40V, Electrolytic capacitor
The max639 has its own current limiter built in set for 200 mA. This is to make sure that charging the NiCads able to handle the continuous current of 200 mA, let’s see the example : NiCad battery packs of 1700+ mA used for electronic aircraft and Radio Control cars.
source : Tony Var Roon’s Circuit Collections