Opinions on install, 2x250w and xantrex C40 cc

tayronachan
tayronachan Registered Users Posts: 3
in Solar Beginners Corner #1
Before I get ahead of myself (or have I already?), I thought it better to ask some questions. Any suggestions are appreciated.

My main goal is to have a little backup power for my laptop, internet connection and a couple of lights during power outages, while still having my bedroom circuit (isolated) running off an inverter connected to batteries. The laptop, internet connection and a light would be run off/in the bedroom circuit. I figure I need about 816Ah in batteries for 2 days x 5 hours usage a day. And I’ll be looking to add another two cs6p-250p panels in the future.

So far I have two 250W CS6P-250P / Vmp 30.1v / Imp 8.3A solar panels, and a xantrex C40 charge controller. The run from panels to charge controller is 40ft. Would it be better to connect the panels in parallel or series?

For batteries I’m looking at buying 4 Duracell GC110 6v 215Ah batteries to make a 12v system, and buying the Xantrex PROWatt SW2000 inverter. Yes, I am trying to "over build", planning for expansion.

My boss who is a licensed electrician is going to help me, although he has no experience with solar installations. He is actually getting a little excited about the project. I would also consider this a test bed to learn with. Thanks.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    #2
    Re: Opinions on install, 2x250w and xantrex C40 cc
    tayronachan wrote: »
    My main goal is to have a little backup power for my laptop, internet connection and a couple of lights during power outages, while still having my bedroom circuit (isolated) running off an inverter connected to batteries. The laptop, internet connection and a light would be run off/in the bedroom circuit.
    If this is your goal, drop solar, solar is good at providing small amounts of energy over a long period of time, rather than, a lot of energy over a small amount of time, It would be better to just have a battery bank charged from the grid or a small generator, if indeed you will be using the system for 5 hours a day.
    tayronachan wrote: »
    I figure I need about 816Ah in batteries for 2 days x 5 hours usage a day.
    amphour without knowing the battery voltage is useless information. How did you calculate this? Is this to 50% of the battery bank's capacity? There is good info in the BATTERY FAQS
    tayronachan wrote: »
    And I’ll be looking to add another two cs6p-250p panels in the future.

    So far I have two 250W CS6P-250P / Vmp 30.1v / Imp 8.3A solar panels, and a xantrex C40 charge controller. The run from panels to charge controller is 40ft. Would it be better to connect the panels in parallel or series?
    These panels and Charge Controller(CC) are not very compatable, the panels are designed to make best use of their area, and not to charge 12, 24, 48 volt systems, you will loose 40% of their output using them in combination with the C40 CC. There are MPPT type charge controllers that will give you optimum charging from these panels, but they are a bit more expensive.
    tayronachan wrote: »
    For batteries I’m looking at buying 4 Duracell GC110 6v 215Ah batteries to make a 12v system, and buying the Xantrex PROWatt SW2000 inverter. Yes, I am trying to "over build", planning for expansion.
    In series the amperage adds in parallel the voltage, so 2x2 this will provide a 12 volt 430amphour battery bank, of which we would suggest not using more than 50%
    tayronachan wrote: »
    My boss who is a licensed electrician is going to help me, although he has no experience with solar installations. He is actually getting a little excited about the project. I would also consider this a test bed to learn with. Thanks.
    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: Opinions on install, 2x250w and xantrex C40 cc

    Welcome to the forum.

    You already have a problem. The C40 PWM controller is not a good way of connecting 30 Vmp panels to a 12 Volt system. Almost half the power will be lost due to the Voltage difference. You need an MPPT type controller any time "grid tie" panels are used with battery systems if you want to get the maximum power from them.

    I don't know how you figured 816 Amp hours of battery, but that isn't going to charge from 500 Watts of panel. As-is you will get about 16 Amps current maximum or <2% peak charge rate. It would maintain but it would not charge. Even with an MPPT controller the rate would be about 4% which is still below recommended minimum.

    In short, that's not going to work.

    Then you talk about four 215 Amp hour 6 Volt batteries. That isn't 816 Amp hours @ 12 Volts, it's 430 Amp hours. With those batteries you have a chance providing you switch to the MPPT controller and get the full 32 Amps out of the panels (7% charge rate). This would mean a 45 Amp or larger charge controller, so you should increase the panels as well: three in parallel would give you 750 Watts, 48 Amps peak current, and 11% peak charge rate. That's just about perfect. Unfortunately it requires a charge controller that costs in the neighbourhood of $500.

    BTW you should consider going to 24 Volts to begin with, even though this is an experiment. It's more efficient and allows for expansion more easily, although it requires a different array set-up (the panels must be in series as the Vmp is too low to properly charge a 24 Volt system).
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  • tayronachan
    tayronachan Registered Users Posts: 3
    #4
    Re: Opinions on install, 2x250w and xantrex C40 cc

    Thx for replying guys. Ok, so it looks like I've already got myself in a bind, seeing as how I've already purchased the C40 cc and the 2 x 250P Canadian panels.

    Cariboo, can't afford a 24v inverter.

    I found this calculator today, http://www.batterystuff.com/kb/tools/solar-calculator.html , inputting 500w usage x 2hrs for 2 days, 12v system, using 3.5 hrs direct sunlight, got me closer. And that would be with two 6v 215Ah batteries. I'm shrinking here :cry: ,my bad tho, and that might not be such a bad thing, I can save on batteries and hopefully still learn.

    I also have 2 x 215w Evergreen ES-A-215-fa3 panels (18.4 Vmp/11.69 Imp), hooked up to a Sun 500w gti inverter (yes gents, I now know I should have bought panels with the same voltage.) Would these work better with the C40 cc and 2 batteries? The 2 x 250P Canadian will run the Sun 500 gti.

    But I am stuck with the 2 x 250Ps and the C40 cc. Wishing I'd done better research. Off to mow the lawn and take my mind off this little dilemma.
    Thx for any help gents.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Opinions on install, 2x250w and xantrex C40 cc

    The Evergreens' Vmp of 18.4 is on the high side of "normal" for a 12 Volt system. They would work much better through the C40 as they will pass all their current and have no large amount of power loss due to Voltage difference. So you'd get 23+ Amps peak. A good current for 215 Amp hours.

    Look at the input specs on that 500 Watt GTI and see if it doesn't have a broad enough range to accept the 30 Volts from the 250 Watt panels.
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  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    #6
    Re: Opinions on install, 2x250w and xantrex C40 cc

    Adding to what Cariboocoot posted, the 18.4 Vmp of the Evergreen panels would help offset Voltage losses due both to wiring between the panels and the charge controller and to high panel temperatures in summer.
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  • tayronachan
    tayronachan Registered Users Posts: 3
    #7
    Re: Opinions on install, 2x250w and xantrex C40 cc

    The 500w GTI DC input specs are 24v to 52v, so yes the 250w panels would work, and I have tested it successfully with those panels.

    So, it's the 2 x 215w Evergreens, the C40, 2 x 6v-215Ah batteries, and a 12v inverter.

    Cariboo, you mentioned going to a 24v system, the C40 cc does have jumpers so it can be set at 12v, 24v or 48v. So there is that option. I do have a lot to learn. I'll come back to update my progress. If there are any more suggestions fire away. Thank you and everyone else again.
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