Ok, this one is simple for you guys, I hope..

Himins
Himins Solar Expert Posts: 54 ✭✭✭✭
in Solar Beginners Corner #1
I used 3.8kw in 54 hours and 45 minutes. My math says something like 1.6 kw per day. If so, I'm still underpowered with 4 panels reporting 1.5kw today. Did I do this right? I may be way underpowered if I lose 30% or more to the battery and inverter.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Ok, this one is simple for you guys, I hope..

    Where and how did you measure?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Ok, this one is simple for you guys, I hope..

    Simple math: 3800 Watts / 54.75 hours = 69.4 Watts per hour average * 24 hours = 1665.75 W hours in a day.
    So if you're only getting 1500 Watt hours per day from the panels you will indeed fall short.

    In AC terms that 1.7 kW hour usage means a need for more than 800 Watt array @ 4 hours of good sun.
    Your 1380 Watt array should yield (1380 * 4 * 0.52) 2.8 kW hours per day.
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  • Himins
    Himins Solar Expert Posts: 54 ✭✭✭✭
    #4
    Re: Ok, this one is simple for you guys, I hope..

    Ok, I was afraid of that. I only have 4 panels installed with 2 strings of 2. I will get 3.5 hours of good sun this time of year, but what puzzles me is this. When I first connected I made one string of 3. All my logging stats appear to be roughly the exact same after I added the 4th panel and used 2 strings of 2 when I was expecting to see a slight increase. earlier this week I shaved 28 linear feet of #6awg wire and moved the batts into a warm/vented room....the end result is about the same or barely less than with 1 string of 3. My panels are delivering about the same amps with 2 strings of 2 as they did with 1 string of 3...somewhere around 5 amps...with 2 strings, I assumed the amps from the panels would run near 10 amps and the voltage would drop by 1/3...which it did.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #5
    Re: Ok, this one is simple for you guys, I hope..
    Himins wrote: »
    Ok, I was afraid of that. I only have 4 panels installed with 2 strings of 2. I will get 3.5 hours of good sun this time of year, but what puzzles me is this. When I first connected I made one string of 3. All my logging stats appear to be roughly the exact same after I added the 4th panel and used 2 strings of 2 when I was expecting to see a slight increase. earlier this week I shaved 28 linear feet of #6awg wire and moved the batts into a warm/vented room....the end result is about the same or barely less than with 1 string of 3. My panels are delivering about the same amps with 2 strings of 2 as they did with 1 string of 3...somewhere around 5 amps...with 2 strings, I assumed the amps from the panels would run near 10 amps and the voltage would drop by 1/3...which it did.

    The only reason that the output from the panels would stay more or less the same is that if that is all that the batteries are accepting. If this is the case, then the problem may be in the voltage setpoints of the CC rather than in your panel setup. Are you using an MPPT controller? If so, then if the batteries are the limiting factor, the product of the current and the voltage going into the CC should be independent of the panel configuration.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Ok, this one is simple for you guys, I hope..

    These panels are around Vmp 30 Imp 7.5?

    If so, the single string of 3 should have had a Vmp of 90 and Imp of 7.5, 690 Watts.
    The two parallel strings of 2 should have a Vmp of 60 and Imp of 15, 920 Watts.

    Output of the FM80 with the first string should be a maximum around 44 Amps on a 12 Volt system.
    Output on the 920 Watts should be around 59 Amps.

    If you've seen an over-all decrease in power it is quite likely there is something wrong with the panel wiring. If possible, switch between one string and the other and see what output you get at any given time.
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  • Himins
    Himins Solar Expert Posts: 54 ✭✭✭✭
    #7
    Re: Ok, this one is simple for you guys, I hope..

    Yes Inetdog, an outback fm80, I could reset, but you have a very interesting point, perhaps my batts are puke which actually makes some sense.
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  • Himins
    Himins Solar Expert Posts: 54 ✭✭✭✭
    #8
    Re: Ok, this one is simple for you guys, I hope..

    My voltage seems quite close to the specs, if anything consistantly higher, the amps didn't change, but Inetdog may have pinpointed the problem...without real batterys like you rich guys!!! I may be getting all these things can take. I'm thinking Inetdog, if I understand this, is suspecting a little too much resistance in the battery.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Ok, this one is simple for you guys, I hope..

    The problem could well be having eight 12 Volt batteries in parallel, as that is almost 100% certain not to work. Especially if they are not connected via equal length wires to common points for (+) and (-).

    These batteries: 90 Amp hour RV/Marine units by any chance? If so, try disconnecting half of them and see if it doesn't work better.
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  • Himins
    Himins Solar Expert Posts: 54 ✭✭✭✭
    #10
    Re: Ok, this one is simple for you guys, I hope..

    I have not tryed just one battery, I have tryed 3, 4, and currently have 5, only because its getting the job done barely. I've touched on this before and never answered the person, but I run a window fan on low into the crawl space under this old farm house. Its pulling 48 watts and if I have sun, the 5 battery solution makes the trip somehow. By creating a slight positive pressure under this house, the floors warm up enough to walk around barefoot, and cuts my wood pile per day in half, don't ask me why, but it works when I used heating oil too.
    When I have some help here...I'm going to connect one battery at a time and determine which battery's have the most resistance by reading the amps from the CC. I'll try to determine which battery has the most resistance with this idea Inetdog dropped in my lap...by the way, THANKS YOU GUYS...ITS COMING...and I just pulled off a 20 below zero night with only 1 hour of generator, last night at 10 below...no generator!
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #11
    Re: Ok, this one is simple for you guys, I hope..
    Himins wrote: »
    ...ITS COMING...and I just pulled off a 20 below zero night ...

    I hope it's not coming this far south, the once a year 10 below, is about all I can handle...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #12
    Re: Ok, this one is simple for you guys, I hope..

    Have you banked the foundqtion of the house with straw oe hay bales? (or snow?). A trick I learned long ago was to freeze the outside of the house with water sprayed from the hose. It may seem counter intutitve, but a layer of ice over the side of a poorly insulated house does wonders to seal out the draft,, most especially at eh crawl space and the rim joist area.

    Depending on the wind, the ice can sublimate pretty quickly, (in a matter of days) but if you have a source of outside water a spray every day or two can keep the crawl space, and the exposed walls sealed up pretty well.

    (snow piled up against the foundation is a big help too, as it is a a very good insulator.

    Tony
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