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

PARTS LIST
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:

    Hello,

    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 http://alltransistors.com/transistor.php?transistor=22314

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

  6. Lyon Bassey says:

    Hello,

    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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