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hobbssb's avatar
hobbssb
Explorer
Feb 17, 2014

Recharging house batteries with generator

We have 2 6v deep cycle batteries and a 2500w LP Onan generator. About how long will we need to run the generator to recharge the batteries from "empty"?

We usually keep the batteries charged with daily driving. However, this last trip was spent with several days parked with no hookups. We ran the generator to recharge the batteries. We are thinking that maybe the control panel which shows the charge of the battery gives inaccurate info. The control panel showed the battery charge as "full" after running the generator only about 30 minutes. The battery indicator read "empty" by the next morning with minimal usage (refrigerator on propane and LED lights and movie for about two hours). We tried running the generator again for 30 minutes, the indicator again read "full", but over the course of about three hours the indicator dropped down to empty.

We are guessing that the batteries really aren't full after running the gen for such short time and that for whatever reason, the indicator panel can't be used to judge how full the batteries really are after running the generator?????

We need your expert advice! Thanks
Class B

17 Replies

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  • mlts22's avatar
    mlts22
    Explorer II
    Feb 17, 2014
    hobbssb wrote:
    Our converter is a Parallax 7355


    Chuck that converter whenever you have the ability to. A replacement three stage converter like pictured above will be cheaper than battery replacement after a boiled battery or two.
  • time2roll's avatar
    time2roll
    Nomad
    Feb 17, 2014
    7355 is a fixed voltage converter supplying 13.6 volts. :(

    I recommend a Progressive Dynamics 4655 replacement.

  • pianotuna's avatar
    pianotuna
    Nomad III
    Feb 17, 2014
    Hi Since you are in a 2012 RV you may have a 3 stage converter. But--we need to know the make and model to give better advice.
  • darsben's avatar
    darsben
    Explorer II
    Feb 17, 2014
    Buy a good battery charger and plug it in while generator is running.
    Will significantly reduce charging time but you may have to replace batteries a little more often.
    Also check electrolyte levels at least monthly.
    It is what I do and I have had no adverse affects
  • time2roll's avatar
    time2roll
    Nomad
    Feb 17, 2014
    Even with an excellent converter to do the charging, it will take 2 to 4 hours to charge a low battery to 90%. Another 6 to 8+ to get 100%.

    You need to be charging in the 14.3 - 14.8 volt zone for a fast recharge. Most oem converters charge slow at 13.6 volts.

    The indicator just shows the instant voltage is above 12.6 and calls it full. It is not full in 30 minutes.

    You may want to upgrade your converter. Post what you have for best recommendations. If you will be doing this off-grid camping more in the future consider 100 watts to 250 watts of solar.
  • mlts22's avatar
    mlts22
    Explorer II
    Feb 17, 2014
    Charging batteries have a curve, and depending on your RV's converter, 30 minutes likely won't add much. You likely will have to run the generator at least for a few hours to get back to a decent charge level (~60%). To get back to 100%, it will need to be plugged in to shore power for a day or two.

    The indicator will read "full" when the generator is on, and briefly afterwards. Then it will drop back to the "real" value. That is normal.

    The indicator lights are OK, but I personally recommend installing a voltage readout (Trimetric is the best brand for this), so you know exactly where you are, and not relying on a set of idiot lights.

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