off grid, questions

cocomitch
cocomitch Registered Users Posts: 17 ✭
in Off Grid Solar & Battery Systems #1
Hi Guys/Gals,
I am writing this for my brother in law, as he is off grid, and no computer, so PLEASE bear with me. He has 8 kyocera solar panels, 4 are 125 and 4 are 120's, rated at 7.6amps , he has a whisper 200 wind genny, 6 l16 395 amp deep cycle batteries set up for 12 volts, he has a trace inverter 2500 12v inverter, and a xantrex c60 charge controller.
He is totally off grid, no power lines for 4 miles, he has a 24x24 cabin, running compact flourescent lights, a tv using minimum watts, a fridge taking 1.1 amps, a freezer using 2.5amps, an energy efficient washer and propane dryer using 1.5amps, not all at once mind you. He has sunlight from 8am till 4pm, he has on average 20-25hr wind, on the lake, the genny furls quite often.
Having said all that, he will have max charge in the batteries during the day, at night, he still has to put the generator on to charge his batteries, they go down to 11.8. we have checked all the wiring, electrician, and everything is connected properly, no ghost loads.

I know that all you solar guru's must have had someone with this same problem throughout the years, can you please help him, his wife is wearing his ears off, hehe.

Thanx for your attention,
Mike
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: off grid, questions

    Welcome to the forum - by proxy, as it were. :D

    Can we just confirm that battery bank? 16 6 Volt 395 Amp hour batteries configured for a 12 Volt system? I sure hope not, because that would be a 3160 Amp hour bank which would never, ever charge properly off 980 Watts of panel. In fact, a bank that size would need 5600 Watts of panel!

    Also, with eight parallel battery strings there would be difficulty keeping current flowing evenly through all batteries.

    So let's check and make sure of the size/configuration of that battery bank. After all, that's the heart of the off-grid system.

    EDIT: re-reading, that could say "6 L16 batteries", which would be 3 * 395 = 1195 Amp hours, which also will not charge well off 980 Watts. It would need 2100 Watts. 980 Watts is really only enough for 531 Amp hours.
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #3
    Re: off grid, questions

    they are 6 (l16) batteries, and 8 kyocera solar pannels, 4 are 120watts, and 4 are 125watts
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #4
    Re: off grid, questions

    sorry 6 volt batteries
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: off grid, questions

    So that's three parallel strings of two each; 1185 Amp hours. A bank that size wants 118.5 Amps charging rate. Since they are L16 ("tall case") they really need the higher current to fight stratification as well as sulphation.

    Let me guess; it worked at first, but now the batteries go dead pretty quick?

    I'm guessing the panels produce about 50 or so Amps?

    I don't suppose he's had a Kill-A-Watt meter to get a daily Watt hour consumption figure?
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #6
    Re: off grid, questions

    your guess is right on the money, no he does not have a kilowatt meter, but he does not use much, especially right now, they are re-building the cabin, so just the freezer, and a small trailer at night. are you telling me that the battery bank is too big for the panels?
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #7
    Re: off grid, questions

    Yea, that's a lot of battery.

    Also, 8 hours of sun is not the same as "8 hours of full sun directly on the solar panels causing them to put out full power". Most static mounted solar (no tracker mount) will only get 4-6 hours of "good sun" per day.

    Also, any shade at all - even on only one small corner of a panel - can be enough to drop that panel's output virtually to nothing.

    He needs a battery monitor. Lots of folks around here know and love the Bogart:

    http://www.bogartengineering.com/products/TriMetric
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #8
    Re: off grid, questions

    he has the pannels set up on towers that he can move the panels toward the sun, no electric tracker, but he is retired and always at home, so he moves them. there is no shade except the clouds, clear from east to west. what will a bogart do to improve his problem? would it be more advantageous to him to just use 2 of his batteries to get them fully charged instaed of all 6 and only get a partial charge?
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #9
    Re: off grid, questions
    cocomitch wrote: »
    he has the pannels set up on towers that he can move the panels toward the sun, no electric tracker, but he is retired and always at home, so he moves them. there is no shade except the clouds, clear from east to west. what will a bogart do to improve his problem? would it be more advantageous to him to just use 2 of his batteries to get them fully charged instaed of all 6 and only get a partial charge?

    The battery monitor would give him a fairly accurate measurement of how much is going in/out of the battery. Armed with that knowledge, he could determine how much he uses/day and thus how much battery bank he really needs, as well as whether or not his current PV+wind is adequate for his needs.


    He'd be better off with less battery as long as it would be enough to supply his loads. If it would just cause him to drain those two excessively (more than 50%) then he'd need the generator anyway.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: off grid, questions

    The Bogart meter will do a good job of keeping track of how much current is actually flowing in to and out of the batteries.

    He should definitely try to fully recharge the batteries, and check the Specific Gravity on every cell. Some equalization charging may be in order, and if this has been going on for long there is the possibility that some or all of the batteries are ruined.

    In terms of "panel harvest" he's probably looking at about 3 kW hours per day. The loads you mention could easily exceed this, efficient units or not.

    Don't count on the wind generator for much; even if it produces well, it would only be a minor contributor to a system that size.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    Re: off grid, questions

    First,

    Here are some good Battery FAQs:

    Battery Connections
    www.batteryfaq.org
    Deep Cycle Battery FAQ

    Second, he should be monitoring the batteries (specific gravity, resting voltage, electrolyte levels, charge/discharge currents, etc.).

    Usually, the first thing we say is to get the batteries under control... Basically, the battery should operate between 100%-75%, can run from 75%-50% but should be recharged > ~75% within a day or so. Also he should never run the bank below 20% state of charge--Or some battery cells can be permanently damaged.

    Storing a battery for days/weeks/months below 75% state of charge is an invitation for sulfates to harden and a short battery life.

    For tall batteries, getting them a 10% rate of charge (with the genset is fine) can help stir up the electrolyte (re-mix stratified layers).

    When we look at loads--we need to know if the amps is at 12 volts or 120 volts... 1 amp * 12 volts = 12 watts; 1 amp * 120 volts = 120 watts--A 10x difference in power used.

    Once the battery situation is under control (probably running the AC charger off of the genset until the batteries are at least 80-90% charged)--then we can start to visit the other questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #12
    Re: off grid, questions

    ok thanx for your advice, i will let him know about the battery meter, and let him decide!
    For the loads that he is using, what would be your recomendation? I appreciate this!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: off grid, questions
    cocomitch wrote: »
    ok thanx for your advice, i will let him know about the battery meter, and let him decide!
    For the loads that he is using, what would be your recomendation? I appreciate this!

    It's difficult to say without a specific Watt hour usage figure.
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #14
    Re: off grid, questions

    ok, i will definately get that from him, i will make sure he knows about the battery meter, i will be getting back to you!
    Thank you so much for your expertise, and help!
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  • zeuspaul
    zeuspaul Solar Expert Posts: 59 ✭✭✭✭
    #15
    Re: off grid, questions
    i will make sure he knows about the battery meter,

    I think a battery monitor is a great idea. However I wouldn't wait as the batteries need attention now.

    Use a volt meter if that's all you have. Rested 11.8 volts is totally discharged. Rested 12.0 volts is 75 percent discharged and I wouldn't go below that. Do whatever it takes to stay above 12.0 volts until you get a better handle on system. If the loads have been cut to the minimum then run the generator to maintain the batteries above 12.2 rested voltage which is fifty percent discharge. I would rest the batteries at least four hours with no load before taking a volt reading.

    What size is the generator?

    http://www.kyocerasolar.com/solar/batteries.html
    By comparing voltage readings to hydrometer readings, shutting off various charging sources or loads and watching the resulting voltage changes, the system owner can learn to use indicated voltage readings with good results.

    Zeuspaul
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  • zeuspaul
    zeuspaul Solar Expert Posts: 59 ✭✭✭✭
    #16
    Re: off grid, questions

    Temperature compensated state of charge using voltage.
    http://www.rpc.com.au/products/batteries/car-deepcycle/carfaq4.htm#ocv_soc

    State of charge using voltage and battery under unknown load
    http://www.marxrv.com/12volt/12volt.htm

    Zeuspaul
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  • cocomitch
    cocomitch Registered Users Posts: 17 ✭
    #17
    Re: off grid, questions

    It is a honda 5500watt, put into his trace inverter charger
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  • peterako
    peterako Solar Expert Posts: 144 ✭✭
    #18
    Re: off grid, questions

    Hi there i have also a whisper 200 you can find some off my comments in this forum for this one. The 1000W ( 80A for 12V ) is a dificult one if your brother has still the orig. tail, then it is furling to early update it to double size using a wheather proof plywood. then your brother wil see that it is more stable.

    The battery is a big oversize for the charging system.
    The problem is that it takes more time and energy to fill up the last 15%.

    greetings from Greece
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