Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to power 375 watt 12vdc motor ?

  1. Sep 24, 2011 #1
    Hi all.
    I am new to this great forum but have perused it many times past picking up some great knowledge.

    I have a rather heavy trailer dolly fitted with a 375 watt 12vdc motor (30amps???).

    I know I can mount a 12vdc battery to drive the unit but adding a battery would make the dolly unbearably heavy.

    Can I use a 240vac battery charger (in lieu of a 12v battery) to power the dolly?
    I do have an "automatic" 6v/12v, 2A/6A/12A charger which also has a battery start switch.

    Please, I am not "electrically" minded so your input here will be welcomed.
    [Have searched previous posts but nothing found relating to my motor spec]
  2. jcsd
  3. Sep 24, 2011 #2


    User Avatar
    Gold Member

    No, you cannot operate the 375 watt 12 Volt motor (30 Amp) with a battery charger.

    The charger will not provide the power needed. It only "trickle charges" batteries, that means only a small amperage is delivered for a long time period to charge the battery. It does not have the capacity (power) to provide all those amps!
  4. Sep 24, 2011 #3
    Thank you Bobbywhy.

    Is there some other device I could use ?
  5. Sep 24, 2011 #4
    You could use a computer power supply. The yellow wires supply 12 vdc.

    Some lighter models may not be able to produce the 31 Amps that you need. Usually this specification is printed on the side or (if you haven't bought it yet) found on the package or the internet.
  6. Sep 24, 2011 #5
    Thank you.
    PC Power Supply is worth a try but, sorry, I just don't know what P/supply to specify.

  7. Sep 24, 2011 #6
    This one would run it. Under the details tab it says the 12v lines will run 53A (and is the cheapest I seen) for <$100. Be careful on what you buy, just because the wattage is over what you need doesn't mean the 12v line will run at that power rating. Good luck!

  8. Sep 24, 2011 #7


    User Avatar
    Gold Member

    I recommend that you do not buy a computer power supply to drive your 12Volt 30 Amp motor. Will you always have your motor near the 120/240 volt mains? Or do you need it to be portable...that is, operate on batteries alone? Then, find out how others operate this motor on the trailer dolly. See




    Google is your friend. Learn to use it for your questions and doubts.
  9. Sep 24, 2011 #8

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    what about a lawn-mower battery? less than half the weight of a car battery and around $23 at Wal mart. Lawn-Garden-Tractor battery they're called, LGT....
    i use one in my little boat.

    okay for runs of a minute or so at your 30 amps.
    use a 4 amp charger to top it off before you leave home, recharge it when you get back. dont store any battery discharged.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook