Car with 3 12v battries. How do I charge?

Discussion in 'The Projects Forum' started by v194, Feb 4, 2010.

  1. v194

    Thread Starter New Member

    Feb 4, 2010
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    0
    I'm very green at electrical issues and could use some advice of how to figure this out. Some facts:
    • I have a vehicle with a standard 12v battery connected to the factory charging system. It works fine.
    • I also have two 12V deep cycle marine batteries in the trunk used to power some 24v and 12v electric motors. They have no charging system unless I take them out and charge them separately.
    Now to the questions:
    • Can I create or buy a system that will charge all three batteries based off the existing vehicles alternator system?
    • Can I create or buy a system that will allow me to run all of the electric motors (not at the same time) from a standard 120-125v wall outlet. In other words can I plug the car "in" and run what I need while the car is on display.
    I appreciate your time and recommendations.
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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    How much current do you need to run the 12-24 volt motors?
    Are the batteries in the trunk connected in series?
    Do the batteries in the trunk have anything to do with the cars electrical system (are they connected to the cars wiring anywhere)?
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Google for "Battery Isolator" I know they make ones with two spigots, maybe you can find one with three. During charging off the alternator, the three batteries will have to wired in parallel, probably using a high-current, multipole switch.

    Since you need both 12V and 24V at the same time, which implies running two batteries in series, you just need two 14V 2A "smart-chargers" wired across the two batteries, with both sets in series. That way, the charge in the two batteries will remain balanced, even though the current drawn from them is not balanced. To reconfigure the batteries for this operation, two that were in parallel during alternator charging will have to be switched to the series configuration for operation and AC charging.
     
  4. v194

    Thread Starter New Member

    Feb 4, 2010
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    0
    Thanks for the reply.
    Like I said I am green to this so please pardon my ignorance in electrical matters.
    The car has several 24V and 12V motors none are run at the same time. The all take their power from the dual 12V batteries in the trunk. Taking the respective voltage for respective motor (It has been wired to work this way)
    The batteries are connected together to provide the 24V
    The trunk batteries have nothing to do with the charging system. They are just wired to the motors. In order for mt to charge them I have to take each out and charge separately, which is getting tiresome.

    I forgot to mention that the 12 system that would run a vehicle normally is in fine shape and runs all of the normal systems of the vehicle. The trunk batteries run only the motors.
     
    Last edited: Feb 4, 2010
  5. gerty

    AAC Fanatic!

    Aug 30, 2007
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    I just wanted to make sure one of the trunk batteries wasn't wired in series with the car battery. Like Mike said, you can get two chargers and wire one to each battery. If you want to eliminate the batteries completely you can substitute with power supplies,one 12v and one 24 volt. Of course you'll have to know how much current each motor draws so you can make sure the power supplies can supply enough current.
     
  6. Externet

    AAC Fanatic!

    Nov 29, 2005
    761
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    If you need to recharge the 2x12V batteries in the trunk fron the vehicle generation, you need to buy a DC to DC converter 12VDC in to 28VDC out capable of the desired charging current.
     
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