Solar NiCad battery charger
This circuit is designed for low power or low Ampere hours Nickel cadmium battery chargers. Up to 12 solar cells are used in this project to charge battery. This circuit can be used to charge small NiCad batteries. Charging current of battery should not be greater than 200mA. I have already posted many articles on high power or current solar charge controllers. You may check following articles:
- Smart solar charge controller using pic microcontroller
- 15A solar charge controller without microcontroller
If you want to design solar controller to charge high power batteries I recommend you to check above mentioned articles. This circuit is designed to charge low Ampere hour batteries.
List of components for solar NiCad battery charger:
Resistors,”R1″,820k,
Resistors,”R2″,75k,
Resistors,”R3″,75k,
Resistors,”R4″,1M,
Capacitors,”C1 / 16 volt,47uF,
Capacitors,”C2 /40 volt”,100uF,
Integrated Circuits,”U1″,MAX639 Integrated circuit
Diodes,”D1″,1N57117,Zener diode
Diodes,”D2″,1N57117,zener diode
Miscellaneous,”L1″,100uH, coil type inductor
 Circuit diagram of solar NiCad battery charger:
Circuit diagram of solar charger for NiCad battery chargers is given below. At the right side of circuit diagram, 12 solar cells are used to charge battery. Integrated circuit MAX639 is used to regulate charges from solar cells to NiCad battery.

 MAX639 function and working:
MAX639 is switching regulator which is used to step down voltage. It provides a wide range of output current. It can provide maximum output current of 200mA in safe range. It has a very high-efficiency due to pulse frequency modulation function. Input voltage range to MAX639 is 4-12 volt. It can provide output voltage from 1.5 volt to maximum input voltage.
 Applications of MAX639:
It can be used in various configurations in many projects. But some of the major application of MAX639 is given below:
- Battery chargers
- Solar chargers
- Voltage regulator
- Dc to dc converters
1N57117,Zener diode is used to provide constant voltage to battery. Share this article with your friends by clicking on social media icons shown below thanks 🙂
how you design solar panel in proteus?
How to design Solar panel in proteus and max 639?
I’ve been looking to build your design but I am having trouble locating the Zener Diode with the number you provided and you do not define a specification or rating on the Diode. Could you please provide additional information on components?
Thank you in advanced.
Best regards,
Paul
The diode is either 1N5117 which is a Zener Diode or a 1N5717 which is a Variable Capacitance Diode.
The diodes are 1N5117 Schotky diodes