Off-grid issues after 1.5 years...

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Chris Miller
Chris Miller Solar Expert Posts: 49 ✭
in Off Grid Solar & Battery Systems #1
Hi everyone,

We've been off-grid for about a year and a half now and we're running 2250 watts of panel and 2 strings of Trojan T-105RE's in a 48 volt config.

For this entire time, we've never had to add water to the batteries even once. I checked them as recently as 3 weeks ago and every cell had water covering the plates. But.... this week we started having issues with the system keeping a charge so I checked the batteries again and found several cells with exposed plates.

We went from having a system that held its own thru the night, to a system that needs the generator by 10pm and again by 7am.

Nothing has changed in terms of usage, so I can only suspect an issue with these batteries.

Where should I go from here? I am attempting to equalize the bank using the generator and the Magnum inverter / charger as I type this but it's been 2 hours now and it's only up to 56 volts and for some reason charging at zero amps. I've never used the magnum to equalize before so I am not sure what I should be expecting.

I really should have gone with a better battery setup but this is what we had the money for at the time. Now i'm thinking it's time to look at fork lift batteries and also go ahead and slap up the remaining 6 panels I have to bring us to 3750 watts total.

I'd appreciate any thoughts / feedback. I hate to go on burning 1-2 gallons of fuel a day. It's just not sustainable.

Thanks!
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
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    Re: Off-grid issues after 1.5 years...

    Exposed plates? OH NOOOO :cry: The outlook now for those batteries is not good, not good at all. You can try to recover them, but I wouldn't expect much from them any more.
    And never having to add water even once in a year and a half - - - that's EXTREMELY unusual and my first thought, right or wrong, is that the batteries were not being brought up to full charge.
    One of the problems with multi-string battery banks is that one string can fail and go unnoticed while the other string takes over the whole load - - then suddenly one day serious problems appear. That COULD have been what happened here, and COULD explain the sudden thirst for water.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #3
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    Re: Off-grid issues after 1.5 years...

    Deficit charging, No water use means insufficient Absorbs with little or no gassing. The EQ for the Magnum is controlled on the Remote, it is both Time and Voltage selectable, it probably in the default settings. What ever portion of the plates were exposed are gone, but you'll have some capacity left if you are able to get the SG level back up. I see no mention of the SG level in the post, without that you just shooting in the dark.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #4
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    Re: Off-grid issues after 1.5 years...

    It sounds like you might have been undercharging the batteries (or drawing too much power). So first double check Battery bank AH vs solar array capacities:

    2 strings * 225 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,724 Watt array minimum
    2 strings * 225 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 3,448 Watt array nominal
    2 strings * 225 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 4,482 Watt array "cost effective" maximum

    And if you have a minimum of 5 hours of sun per day this time of year:

    2,250 Watt array * 0.52 system eff * 5 hours of sun = 5,850 Watt*Hours typical useful 120 VAC per day

    Have you measured the specific gravity of your batteries over time?

    And have you kept track of your bank (and 6 volt battery) voltages? Watching them can give you an idea of how everything is working.

    Never having to add water--That usually is a sign that they are not really getting a good charge on them.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #5
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    Re: Off-grid issues after 1.5 years...

    Well id say treat this as your learner pack and having got your moneys worth (theres always a bright way to look at things).

    T105s for a multi kw system were never going to last a heck of a long anyway, but before you invest in a new bank, you had better get your basics sorted, as referenced above.

    Do you have whizbang, or equiv reliable end amps regime in place? Is there a thread here that we can refer to, that outlines your system design?
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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