RV battery care and feeding

Shadowcatcher
Shadowcatcher Solar Expert Posts: 228 ✭✭✭
in Advanced Solar Electric Technical Forum #1
Our teardrop trailer has a185W high voltage panel feeding into Morningstar MPPT and then into a Lifeline 150 AH AGM. I keep it for the most part at 100% SOC. This is also what many/most RV owners do leaving the RV plugged in and the converter on float.
The question is would it be better to cycle the battery.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: RV battery care and feeding

    The issue is value: it's going to die over time anyway, so not making optimum use of the cycle life is money lost. What constitutes "optimum use" is debated frequently. And of course with an RV you really can't cycle it daily.

    On the whole I wouldn't worry about it too much. Not cycling them doesn't do any significant harm to lifespan that I can see.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: RV battery care and feeding

    i kind of differ in that opinion as i believe cycling will help a tad with the life of the batteries as long as it is not too deep or too shallow.

    now as to a converter constantly feeding it a float voltage, this is not good imo. solar is almost ideal because nightfall gives the batteries a rest from the charge process as such to relieve some positive plate migration and other possible things from occurring. if one only has such a choice as to leave it on at all times and it's possible that you can vary the float voltage that you should put it at the lowest recommended float voltage possible. i think this would be the same range as for a sunxtenders for your lifeline at 13.2v to 13.4v for a 12v battery. that means placing it at 13.2v and i doubt it would hurt at 13.1v if not to be left alone for too long of a period of time like in months. this also means that one should have the temp compensation as well to get a better handle on the proper voltages for the battery due to temp variations. i view the bts as a must.
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  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    #4
    Re: RV battery care and feeding

    This has been helpful in really understanding what is happening. One option, since it is an AGM is to disconnect it during winter or periods of inactivity and let it sink rather than keeping it at 100% SOC. It has temperature compensation and is monitored by a Victron battery monitor Cariboocoot has a point in that it will age out before damage will be a factor. niel has a point for those that do leave their rigs plugged in (I do not), but then the big RV's tend to have a number of vampire loads even when the batteries are "disconnected" i.e. radio memory/presets or the perennial "I have no idea why my batteries go dead in a couple of weeks". When I turn the 12V disconnect switch the only thing still connected is the battery monitor.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: RV battery care and feeding

    those loads, even though small, will take away from the battery over time if no other charge source is connected of sufficient current capacity. with phantom loads it would be better to leave the float charge on all of the time to compensate. batteries must be at 100% soc before reaching a float condition which means it must go toward the 14.3v area and stay there for quite awhile for an absorb charge before going to float. if your battery is going dead over a few weeks of being totally disconnected with no loads after receiving a full charge then that battery is compromised and is not doing very well. how much the battery is dissipating as opposed to receiving you need to have a better handle on and monitoring the battery with a battery monitor helps. you may want the battery to be load tested to be sure of its condition.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #6
    Re: RV battery care and feeding

    "When I turn the 12V disconnect switch the only thing still connected is the battery monitor."

    Except for federally mandated LP Gas & CO detectors, and possibly the Test panel.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: RV battery care and feeding

    those are loads and are draining the battery slowly over time until dead.
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