Exercising my battery bank while away

Hairfarm
Hairfarm Solar Expert Posts: 225 ✭✭✭
in Off Grid Solar & Battery Systems #1
Greetings,

I have a question for those that have an off-grid system and are not at their cabin full time. I have a 12 volt system @ 674ah. Sometimes I'm away from my cabin for 5-6 weeks or more. I've heard that batteries need to be discharged at least 5-10% every few days or they can die early (?)

Is this true? If so, does anyone have any suggestions to keep my batteries "exercising" while I'm on extended leave from the 12v system? Any tips from those who also have to take extended leave from their off-grid systems? I was thinking putting some loads on a timer and leaving my inverter in load-sensing mode.

thanks,
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
    Hi Hair farm,
    If you'll only be away for 5 or 6 weeks at a time, all you need do is ensure the battery bank is fully charged before you leave, then disconnect all loads, even the input. All will be fine as long as they're fully charged adn have no loads. After 6 weeks I would suggest they get a top up charge to replace what was self-discharged within the batteries themselves. They do not need to be discharged every few days and I most definitely would not do that. The key is to keep them charged by doing a top up charge every month or so. What you were told was probably derived from the belief some have that in normal use and being cycled every day, they should be cycled 5 or 10% instead of only 2 or 3 %. However, that does not apply to batteries in storage for 5 or 6 weeks or longer at a time. In that case, don't discharge them, just ensure they stay charged.
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #3
    If you'll only be away for 5 or 6 weeks at a time, all you need do is ensure the battery bank is fully charged before you leave, then disconnect all loads, even the input.

    Are you saying that I should also disconnect the charge controller too while I'm away too, and just come back every six weeks to do a top up. Is there a downside to leaving the charge controller on while I'm gone to keep the batteries charged? Obviously I would disconnect all loads.

    thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    For flooded cell batteries in a relatively warm climate stored more than 30 days... It would probably be best that you disconnect your loads and leave the solar panels and charge controller connected (and properly configured/programmed).

    Self discharge of the flooded cell batteries will make for a sulfation problem--Especially if longer than ~1 month (flooded cell batteries can lose 25% of their charge in a month--depending on lots of things).

    More or less, if you trust your charge controller, leave the panels connected. If you don't trust your controller--You may have other issues (or it is simply a new install).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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