1. drummondislebsd

    Thread Starter New Member

    Dec 4, 2008
    I have a seasonal house that is off the grid, meaning no power connection. We have a gravity feed water system. Charging the water system requires operation of a 15 amp/120v pump for about 30 minutes. This is currently done with a 2500W generator.

    We are considering purchase of a 2500w/5000w power inverter as a generator alternative.

    I read a bit about dc/ac conversion, ohms etc, and my eyes glazed over.

    ....recognizing the inverter will supply the power to operate the pump....

    My questions are;

    a. Should I be concerned about the inverter draining all the battery power out of the vehicle's battery during the 30 minutes of run time?

    b. Is there a potential for the inverter to over tax the car alternator during the run time and burn it up or cause other electrical problems to the vehicles's electrical system?

    c. If I run additional batteries in series, will that "insulate" the car battery from drainage?

    d. Are there other solutions or other concerns that I am not smart enough to even think about?

    I appreciate any assistance.

  2. mik3

    Senior Member

    Feb 4, 2008
    The pump needs 1800W to work according to the current/voltage values you gave. Thus the current will be drawn from the battery equals 150 Amps. Thus it must be a big battery as not to get overheated and get damaged (or maybe explode). Also, if you run the inverter while the car is on, the current will be drawn from the car's alternator (if the voltage does not drop below the battery's voltage) will be 150 Amps. I do not think the alternator is capable of providing such a large current.

    Its better to use two large car batteries (200Ah each) to power the inverter and then charge them with a charger. My opinion, is to stay with the generator.
  3. SgtWookie


    Jul 17, 2007
    The largest alternator that GM makes is rated 130A (roughly 1800W). Most vehicles have alternators rated much less than that.

    Stay with the generator for the time being. You would need a very large bank of batteries to power such a pump motor, and then a way to charge them back up within 12 hours.