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Paralleling and Series Battery going dead question

  1. Sep 13, 2010 #1

    ISX

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    I attached a pic of what I am trying to do. Now if the alternator is 12V I can charge the 2 batteries on the right but I can't charge the battery on the left without taking the blue wire off. I have a 24V inverter that is 1500watt and was wondering what would happen to the battery on the left if I had the truck running so the 2 batteries on the right stayed charged but the left battery was not being charged. Would it simply discharge and I be back to 12V or what exactly would happen? Is there any way at all to charge all 3 batteries at the same time without sending 24V to the truck and blowing all the circuits up, but still have a connection for 24V hookup?
     

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  3. Sep 13, 2010 #2
    Presuming that all those batteries are 12v and the same type, I believe putting 24v across them, as you show with the yellow line, will charge them all. However I further believe that the two in parallel will not be fully charged -- or conversely -- the single one will over-charge...

    I'm not sure what you are attempting to do, but probably the easiest thing would be to put all the batteries in parallel, charge them, and then switch one out into the series connection to get your 24v. A DPDT switch with the necessary current rating would do nicely.
     
  4. Sep 13, 2010 #3

    ISX

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    The yellow lines were just to show where I could get 24V from, not the charge voltage. I want to charge it with my truck so it has to be able to charge with 12v and not send 24v back into my truck. I want to charge all 3 batteries but also have a spot to hit off of for getting 24V for the inverter. The blue line is where the batteries go into a series. I have read about the switch but just wonder if there was a way to do it without them. I also still wonder about the scenario of running the inverter with the truck charging the 2 batteries on the right and not the one on the left, would it kill the battery on the left or what?

    Thanks
     
  5. Sep 14, 2010 #4
    The yellow wires are also where you would have to connect a 24v charger.
    To charge a 24v battery you need a 24++v supply, can't be otherwise... So I think your best option is to do what I said before and switch them all into parallel, charge, then switch one into series to use.
     
  6. Sep 14, 2010 #5

    ISX

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    Dang! Thanks for the help!
     
  7. Sep 16, 2010 #6
    In general it's not a good idea to have batteries of different capacity in series....that's what you have with the two batteries on the right in series with one on the left. As Schipp implies, over time you'll over charge the single battery on the left.

    If you want to power a 24 volt inverter on a regular basis, use two similar batteries in series rather than the arrangement of three you have pictured.
     
  8. Sep 16, 2010 #7

    ISX

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    I guess I will just get rid of it and get a 12V one. You guys have been a great help!
     
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