Voltage Inverter Questions

Discussion in 'Lawn Mowing' started by dobehap, Feb 6, 2004.

  1. dobehap

    dobehap LawnSite Senior Member
    Messages: 292

    For my enclosed trailer, I want to have onboard 110 volts.

    I have two options.

    1st. Generator. Will be installed on trailer tongue.
    4000watt continued power, and like 8000watts surge. 9hp engine. about 14hr run time on 6 gallons of gas. About $500.

    Pros: Pleanty of continuos power for all my needs.
    Cons: BIG!!!! and LOUD!!!!!!!!!!

    2nd. Power inverter. I have a 600watt power inverter, and I have realized that this thing is useless. It cant even power a 4.5amp drill. I have no clue how many watts is 4.5 amps. Sure it will run battery chargers, lights, small stuff. But I need to run power tools, lights, 3/4 hp 15amp GRINDER.
    Question, how many watts do I need?
    Ebay has a 5000watt for around $500 and 3000Watt for around $300

    Pros: Cheaper than generator if 3000watt is enough...is it enough?
    Pros: Small!!! Compact, will go inside the trailer.
    Pros: Quite!!!!- very important.

    Cons: How much batteries do I need to power this thing and how long will it last? I'm thinking about putting two truck batteries in parralel inside the trailer.

    Question, can I run two wires from the trailers run away battery so these batteries will get charged with the run away battery, or does the run away battery doesnt get charged? I dont know...

    What are my other methods of charging these batteries AUTOMATICALly, basicly from the truck power source.
    Is 2 batteries enough, or do I like need 4?

    Thanks for all the help.
  2. LawnPerfect

    LawnPerfect LawnSite Senior Member
    Messages: 318

    Aside from extra batterys to power that inverter, you will need a switching system or isolator system for the batterys. Then you will need a he11 of an alternator to charge them (between 400-900 bucks). I would go with a gen or even a cord to power everything. On a past enclosed trailer I used a retractable cord reel inside the trailer with a door on the outside to pull the cord through. Just pull out the cord and plug it into the wall and you have your power.
  3. NickN

    NickN LawnSite Bronze Member
    from Alabama
    Messages: 1,009

    To find how many watts anything puts out,multiply I(current) x E (Voltage) = P(power)
    I x E

    So a 4.5 amp drill at 110 volts is pulling 495 watts RMS.

    To find current(I),divide P(power in watts) by E(Voltage)
    To find voltage(E),divide P(power in watts) by I(current,ie amps,milliamps)

    Go with the generator.There's a reason why we still rely on fossil fuels.Power!
  4. dobehap

    dobehap LawnSite Senior Member
    Messages: 292

    Retractable chord will be used when I'm stationed, I need power when I'm on the road, and no plug anywhere.

    Ok, if the batteries dont get charged....how long will they last, on the inverter it shuts down when the voltage drops below acceptable level, so the batteries wont be over drained.
    Say I'm drawing 15amps (grinder), what is the run time before the batteries die... say two batteries in paralel. ~700amps each.
    There must be a formula to figure this out.
    If I trickle charging them wont be enough from the truck, I can just charge the batteries next time I'm parked by the plug.
  5. dobehap

    dobehap LawnSite Senior Member
    Messages: 292

    I'm really trying to see if I can get away with an enverter.... I know generators are great, but the NOISE, I dont like the noise...size to, but not as big deal as the noise.
  6. dobehap

    dobehap LawnSite Senior Member
    Messages: 292

    15amps X 115 volts = 1725 watts.

    It seem that a 3000watt should be enough. I think.
  7. ProMo

    ProMo LawnSite Bronze Member
    Messages: 1,468

    theres plenty of sound insulating material availabe to build a box for a gen. look at motor home setups they use gens and are not that loud
  8. LawnPerfect

    LawnPerfect LawnSite Senior Member
    Messages: 318

    Are you really going to be running your grinder while going down the road?
  9. NickN

    NickN LawnSite Bronze Member
    from Alabama
    Messages: 1,009

    You can't go by cold cranking amps.That is only the amps available over a 30 second period when starting.Look at the amp hour on the battery.(Deep cycle of course)
    Batteries AH(amp hour) is based on a 20 hour rate of discharge.So a battery with 30AH rating has a discharge rate of 1.5AH.(30AH/20 hours = 1.5) Which means you could run a 1.5 amp motor for one hour before the battery is drained.
    Just FYI.A deep cycle Optima battery is 65 AH peak.65/20 = 3.25 Amps per hour.So your 15 amp grinder is going to run about 13 minutes before your battery is drained ( one battery).For an hour of running time,you'll need 5 batteries wired in parallel.
  10. dobehap

    dobehap LawnSite Senior Member
    Messages: 292

    not when I'm driving, just when I'm parked away from an outlet.

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