Ni-Cad Battery Charger with LM317

A simple circuit used to charge old Ni-Cad cells for your electronic project. A solar version of the battery charger included. (3/3/2008)


ni-cad battery charger.

Simple Ni-Cad Battery charger

A LM317 regulator is used to regulate the voltage and current for this circuit. This battery charger should be used only for Ni-Cad cells. Other type of batteries (li-ion, NiMh, Lead and Li-ion polymer) needs special care so it cannot be used.


The four cells are charged with a current of approximately 50 mA. For smaller batteries, the resistor can be changed to 24 or 30 ohms.


I'm using this circuit to charge a Ni-Cad battery pack and use it for some electronic projects. I even can use solar cells to make a charger, here is the circuit:


Solar Battery charger The Solar cell provides about 12 Volts and 60mA. The LM317 regulates the current for the batteries and keeps a constant current. I already tested this circuit with my Sun Tracker with good results.


The main component of this charger is a LM317. It's an integrated three-terminal adjustable linear voltage regulator. It supports input voltage of 3V to 40V and output voltage between 1.25V and 37V. It has a current rating of at least 1.5A although lower current models are available.


LM317 Here are the specifications according to the manufacturer:


Vout range: 1.25V - 37V
Vin - Vout difference 3V - 40V
Operation ambient temperature: 0 - 125�C
Output Imax: >1.5A
Minimum Load Currentmax: 10mA


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