Ni-Cd Power Supply Resistor

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  • kodiac
    Senior Member
    • Jul 2010
    • 116
    • Canada

    #1

    Ni-Cd Power Supply Resistor

    I would like to know how to calculate the value of resistor R1 in the enclosed Ni-Cd Power Supply photo.

    Thank You
  • kodiac
    Senior Member
    • Jul 2010
    • 116
    • Canada

    #2
    Re: Ni-Cd Power Supply Resistor

    photo
    Attached Files

    Comment

    • sam_sam_sam
      Badcaps Legend
      • Jul 2011
      • 6037
      • USA

      #3
      Re: Ni-Cd Power Supply Resistor

      Use an online ohm calculator you need
      18 volts @ 500 milliamperes or
      25 volts @ 500 milliamperes the resistor value will a little bit higher
      Use at least 2 watt resistor for this device at a minimum

      If you use this method above do not leave the battery on the charger continuously this will shorted the life of the batteries

      However you would be better off if you used something like a LM317 voltage regulator in current mode this will give you better current control which can also be found on how to use it in current mode in the data sheet for this device

      If you use a voltage regulator in current mode I would recommend that you use 50 milliamperes and 500 milliamperes if you want to leave the battery on the charger all the time use the 50 milliamperes mode and if you want a faster mode charging mode use 500 or 750 milliamperes just make sure that you switch it back to the lower current mode after charging if you leave it on charger

      I hope this helps you
      Last edited by sam_sam_sam; 09-26-2021, 03:57 AM.

      Comment

      • stj
        Great Sage 齊天大聖
        • Dec 2009
        • 31003
        • Albion

        #4
        Re: Ni-Cd Power Supply Resistor

        14ohms
        and it's going to generate 9w of heat!
        (so maybe consider a chinese intelligent charging module instead!)

        Comment

        • sam_sam_sam
          Badcaps Legend
          • Jul 2011
          • 6037
          • USA

          #5
          Re: Ni-Cd Power Supply Resistor

          Originally posted by stj
          14ohms
          and it's going to generate 9w of heat!
          (so maybe consider a chinese intelligent charging module instead!)
          Here is one of these chargers

          https://www.ebay.com/itm/23346573025...IaAq7rEALw_wcB

          One note about these battery charger do not get the idea that you can put a led on the charging board remove all components from the device board and use jumper wires because if you do not do this the charger will not work correctly I have tried this before and the results were that the charger keeps charging the battery instead of lowering the current when fully charged or refuse to charge the batteries

          If this person is building from ground up and designing this charger to charge nicad batteries the same thing will hold true do not add a led at the battery pack you would have the same exact results
          Last edited by sam_sam_sam; 09-26-2021, 04:31 AM.

          Comment

          • sam_sam_sam
            Badcaps Legend
            • Jul 2011
            • 6037
            • USA

            #6
            Re: Ni-Cd Power Supply Resistor

            Here is the website link to the connector for the charger from the same seller

            https://www.ebay.com/itm/23416696459...53.m2749.l2649

            I have bought some of these myself

            Comment

            • stj
              Great Sage 齊天大聖
              • Dec 2009
              • 31003
              • Albion

              #7
              Re: Ni-Cd Power Supply Resistor

              for that money you could get a B6 clone!

              Comment

              • kodiac
                Senior Member
                • Jul 2010
                • 116
                • Canada

                #8
                Re: Ni-Cd Power Supply Resistor

                My diagram is of a Jobmate Ni-Cd charger
                Board # KW14-V0
                R1's outside coating has burned away,leaving no color code bands
                In circuit R1 measures 3.9 ohms

                Are these formulas correct

                VR1=1.17 x Battery Voltage + 3.3v

                R1 = 3.3 / (1/4 of Battery Voltage)


                Thanks to everyone for your information.

                Comment

                • sam_sam_sam
                  Badcaps Legend
                  • Jul 2011
                  • 6037
                  • USA

                  #9
                  Re: Ni-Cd Power Supply Resistor

                  Originally posted by kodiac
                  My diagram is of a Jobmate Ni-Cd charger
                  Board # KW14-V0
                  R1's outside coating has burned away,leaving no color code bands
                  In circuit R1 measures 3.9 ohms

                  Are these formulas correct

                  VR1=1.17 x Battery Voltage + 3.3v

                  R1 = 3.3 / (1/4 of Battery Voltage)


                  Thanks to everyone for your information.
                  Okay

                  Like what was mentioned earlier in this post if just replace the resistor the same exact thing will happen again because this is the cheapest way to charge a battery which has all kinds of issues

                  Comment

                  • kodiac
                    Senior Member
                    • Jul 2010
                    • 116
                    • Canada

                    #10
                    Re: Ni-Cd Power Supply Resistor

                    Thank You

                    Comment

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