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A Single Transistor SS Charger for Small Laods

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  • A Single Transistor SS Charger for Small Laods


    I built a solid state charger for small batteries like AA, AAA, C, D, 9v, 6v, small 12v and I thought I would share the build with the group.

    It is wired normally for as an SG circuit except moving the trigger to make it run SS.

    I learned how to do that from Patrick’s videos a long time ago and he deserves credit for teaching many of us how to do it, so thanks Patrick you have really shared a lot over the years and it is appreciated.

    Some details about the charger:

    The diodes are both 1N4007
    Transistor is MJL211194
    Base resistance is 750 Ohm (two quarter watt 1.5k in parallel)
    The pot is about 1k
    The wire is 21awg for both 75ft.
    The hookup wire is 18Awg braided.

    Here is a picture of it.

    Click image for larger version

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    The first chart is of a 9v Ni-MH. This charge was pulling about 200ma from the primary.

    Here is a video I shot while doing these sample runs:

    Click image for larger version

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    Next we have a AA battery. It is a 3000mah 1.2v Ni-MH. This charge pulled about 50ma from the primary.

    Click image for larger version

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    I finished up with the 5AH 12v that was the primary in the first two charges, just topping it off. This charge was pulling between 600 – 700 ma from a different primary.

    Click image for larger version

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    The charger is intended for small loads, versatile enough to charge multiple sizes. Flashlight batteries, meter batteries & stuff like that mostly.
    Last edited by BobZilla; 11-01-2015, 07:46 AM.

  • #2
    Looks great man! This would be really useful...lots of stuff around the house to power with AA's and 9V.


    • #3
      Thank you Bob Z, for sharing, esp. the charts for the AA and the 9v. If I might ask, in which chg. mode are you set up? I currently use one similar for the same job. 28ga.X3 at @80',with one 3055. It is strategic in that I use it to rechg. my coll. silver kit. I use a 5.3v wall wart as a primary mostly. However, with a gen mode option on board I have been able to cycle my 4 9v batts through using the two modes and increase the over all chg. level. at least enough to make some more silver. Thanks for the charts


      • #4
        Thanks for the feedback guys.

        Dennis that one is running in mode1.

        I should mention that this is not the first one of these I have built. It is based on one I made about two years ago where the specs are the same but I laid out the components differently. I can say that with the 9v they DO last a long time with repeated use. I use those batteries on all of my multimeters. I purchased the batteries over a year ago from a china supplier and have been charging them up very day or two without any issues. They are basically in constant use but of course the meters do not put a heavy load on them. I have not had the AA's nearly as long but so far they have charged right back up and I use those in my tv controller and flashlight. I was concerned originally if the Ni-MH would work well or not but they do work nicely. They sem to be more available these days than the old Ni-CD.

        Anyway that is my experience with this system, Ni-MH cells in mode 1 charging works very well and does not fail in a few months. I'm pretty sure if I had used an off the shelf charger for those meter batteries I would have had to replace them by now but I do not know that for sure.

        By the way this charger has been tested with 6v primary and it does work but I really designed it for 12v source since that is much more common.