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    This NiCd baterry charger circuit schematic can charge 6 volts as well as 12 volts NiCad batteries. It uses a transformer which can deliver 4 to 5 A current between 12.6 and 15 V. Ordinary chargers select the charging voltage through a swith but the circuit featured here uses an automatic current regulator.

    The charging current is automatically regulated to 4.2 amperes. Once the charging current reaches 4A, the voltage drop at R1 will be 600 mV. In this case the transistor T1 will conduct and supplies current to T2.
    Transistor T2 in turn, shorts the base of T3 to ground thereby reducing or totally cytting off the base bias current of T4. The voltage difference between the collector voltage of T4 and the actual charging voltage of the NiCad battery is dissipated by T4. The power dissipation of T4 is therefore the product of the voltage difference and the charging current. In charging 6 volt batteries, the power dissipation can reach up to 40 watts, therefore you must mount T4 with a cooler.

    NiCd battery charger circuit diagram

    nicad battery charger schematic

    Printed circuit layout for battery charger

    battery charger pcb

    Parts placement for NiCd battery charger

    battery charger parts placement

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    12 Responses to "NiCd Battery Charger Circuit"

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    1. sujana md says: on June 2, 2009 at 4:07 am

      i try your projec for my home

    2. only thank you

      best regard
      kazem

    3. Areaman says: on July 9, 2010 at 10:58 am

      This site has very helpful information

    4. sir this kind of diagram can we consider this as a fast charger? Tell me please….

    5. alireza bagherian says: on December 30, 2011 at 3:21 pm

      Tr1 is inverse (colector and emitter), why?

    6. caesar.tabriz says: on April 26, 2012 at 12:33 pm

      thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you

    7. Tr1 is inverse (colector and emitter), why?

      Because you need that voltage drop on R1 to lower the voltage on T1′s emitter. So the T1 emitter will have lower voltage than the base and it will conduct. (this is a verry short explication but this is the main ideea)

    8. what is F1??

    9. thank you sooo much P.MARIAN

    10. can i modify this to charge a 3.6V NiCd battery?

    11. can i modify this to charge a 3.6V NiCd battery? if so, what part will I change?

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