Ni-MH Ni-Cd Adjustable Constant Current Charger

Ni-Cd Ni-MH Adjustable Constant Current Battery Charger

Ni-Cd Ni-MH Adjustable Constant Current Battery Charger Circuit

This is a Adjustable Constant Current Ni-MH or Ni-Cd battery charger circuit. It can be used to get a constant current power supply. Here is the schematic diagram of the circuit:

Ni-MH Ni-Cd Adjustable Constant Current Battery Charger circuit

R1 100Ω
VR1 500Ω Preset
C1 0.1µF
C2 0.01µF
D1 1N4001
Q1 BC140
IC1 LM317

This circuit can be adjusted to any value from a few milliamp to about 500mA. The max current is 500mA because it is the limit of the BC140 transistor in the current-limiting part of the circuit.

The input voltage has to be 5.25v above the required output voltage, because of 1.25v across the current-limiting section and Approximately 4v is dropped across the regulator.  The LM317 3-terminal regulator will need to be heatsinked.

LM317 pinout configuration

the LM series of regulator is suitable for this circuit because they have a voltage differential of 1.25v between “adj” and “out” terminals.

BC140 NPN transistor pinout

For example, to charge 4 Ni-Cad cells, just connect them to the output and adjust the 500Ω preset until the required charge-current is obtained. The charger will charge 4 Ni-Cad cells at the same current. But, don’t forget to turn off the charger before the cells are fully charged or the battery will be over-charged.

LM317 Regulator Adjustable Constant Current Charger LM317 Adjustable Constant Current Ni-Cd Ni-MH  Battery Charger

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7 comments on “Ni-MH Ni-Cd Adjustable Constant Current Charger
  1. cerebro says:

    muy buen diseño,gracias

  2. Lahiru says:

    Can I Use BC 547 instead of BC140? if not what Can I Use?????

  3. Ramana Madishetty says:


    Very well explained.
    Need a suggestions. Can i replace Diode with 1n4007 and 0.001uf with 0.1uf? Hope there will be no big changes with capacitors. Sorry, Correct me if i am wrong.

    Reply will be appreciated 🙂

  4. pauspam3 says:

    Equivalent transistors can be found via a link on

  5. How can charge to 6 cells with this, and volt out capacity (normal and discharge) thanks

  6. Lyon Bassey says:


    Please can one use this charging circuit to charge Lithium Ion Batteries? I have a 4,200mAh,3.8V(15.96Wh)Li-Ion battery for my android phone,I was thinking of using this circuit to charge it but with current of about 870mA-1000mA initially then when the voltage approaches 4.2V,I then adjust it to maybe 300mA or less

    • Alejandra says:

      Hi, no. You can not use this circuit to charge a li-ion battery. When charging li-ion batteries you need to limit the charging current.

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