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MPT-7210A solar charge controller for charging bike packs from 12v

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    MPT-7210A solar charge controller for charging bike packs from 12v

    Question keeps coming up how to charge an Ebike pack from a 12v source like an automobile. AZguy found this MPT-7210A solar charge controller as a possible option. I got mine today and did some quick tests using a an 18v nicad tool battery and it seems like it may work. I used my bench power supply so I could easily monitor the current draw. Had it set to 12.6v and 5a limit. I had to take apart a dewalt charger to tap into it and see what it did for voltage and current. Turns out 20.7v and 2.8 amps. I set the controller for 12v solar. 20.7 and 2.8. When its pulling the full 2.8 it maxed out my supply at 5a and pulled the voltage down a bit. Seems like the draw on the 12v is about double what its putting out to the battery. I will have to do the same test again with an inverter and regular charger to see how the efficiency compares.

    #2
    Unless I'm mistaken you'll see roughly the same with an inverter.
    The efficiencies are nearly the same for a load this small. You have the same power source do the same amount of work.
    on a step up converter with 12v line and 60v load(52v ebike pack), feeding the load a constant 2.5a requires the line to supply 12.5a before efficiency loses.
    If loads were greater you would likely see a larger difference in efficiency.

    I can't say for sure with ni-cad but with lithium chargers you need a pure sine wave inverter. Chargers for tool batteries hate messy power supply.

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      #3
      I received mine but won't have time to fuss with for about a week most likely

      I have a nice 14V 25-30A supply I'll use to replicate vehicle power for testing on the input to the charge controller and several 48/52V bike batteries I'll try on the output of the controller

      The power supply is a very cute little guy from the guys who do the anderson connectors - I've had a couple for years to test/run equipment normally power from vehicles and they are really nice with a lot of good clean power:

      https://powerwerx.com/ss30dv-desktop...pply-powerpole

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        #4
        Got some time to mess with this and it is limited what it can do at 12V (~13.5V).. couldn't get more than about 1.6A but it worked well to that point

        I hooked it up to a 30V/10A bench supply and then it gave me 2.8A (~141W out with ~147W in so just shy of 88% efficiency)

        Would take a long time to charge from 12V though. If you were doing a long drive maybe

        If you have a diesel with 24V a bit better

        The terminal blocks are too small for thick wire. I tried 12AWG but too big. I think I would remove the panel and connect ring lugs crimped to heavy wire.

        It's pretty simple to use

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          #5
          There is another thread that got linked to this one where the person is asking if there is a way he can use his SURON 60v battery to charge I think he said a 36v pack. I don't think this controller can do that. Seems like when I was testing with my 18/20v tool batteries if I cranked by source up to 30v the output also went to 30v which didn't make sense but I could have missed a setting. IF input was 12ish it seemed to boost up to 20 just fine.

          I thought that was the point of a solar controller that the 'raw' solar input could be all over the place and a controller like this could boost or cut the voltage depending on the conditions? But I also don't know that much about solar so maybe the panels now have some built in regulating? And this specific controller is made to work with those? Anyway my testing was using it in boost mode which it seemed to do fine and it sounds like AZ's testing was the same.

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            #6
            Most solar controllers are "buck" convertors. They maintain the voltage parameters for the battery at a lower voltage than the source. The 7210 and a few others " boost" the voltage.
            They do have limits as to their highest amperage that they can process.
            B
            ​​

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              #7
              I have not had the time or a good reason to do any further testing with the unit. I probably should just so I know it will work or not work but hey its more fun to wait till I really need it and then find out if it will work right?

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              • Gr8fun
                Gr8fun commented
                Editing a comment
                I have been wondering if I could use the 7210a to charge from 52 to 52 volt batteries. This might actually be useful for me.
                As a solar charge controller, it is not a good pick. Cheap and versatile. Slow, but that is good for the battery. When you have 10 or 12 hours of sunlight anything above 1.5 amps will give a good amount of charge.

              • AZguy
                AZguy commented
                Editing a comment
                It will work, just slowly - as mentioned at 12V in I could only get about 1.6A charging current on 48/52V batteries

              #8
              Charging my extra battery at home will allow me to recharge at night. Lots of hours at night
              thanks.....

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                #9
                If a need for faster charge is needed, just use two 7210a controllers in parallel. Even using 12 volt battery and a solar panel. I tried that with the 7210a and a genasun controller o er 3 amps charge rate.

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