C n C my System

emcc
emcc Solar Expert Posts: 44 ✭
in Off Grid Solar & Battery Systems #1
I had started a thread a long back regarding a off grid 6kW system. After a lot of research. I am planning to go for a Local Made Inverters/CHargers rather importing that gives me a peach of mind in case I need to get anything replaced.

The one I selected is 3000VA rated at 95% Efficiency HyBrid Inverter Charger. With input of 500Voc with an MPPT system.

I am planning i installing two of them. Battery voltage rated at 48V. I don't need any backup as I am having a 40KVA DG which will serve in case of no Sun.

So I will be only installing 4 (@12v) or 2 (@48v) batteries each to up the voltage at 48v.

Since the max is 450 to 500Voc, I am planning to install panels, which are 64.5Watt rated at 22Voc, with three strings of 20 each (440Voc)

20 x 64.5 = 1290Watt (in series)

1290W x 3 = 3870Watt at 440Voc. (in Parallel)

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: C n C my System

    Even if you don't need reserve power storage in your batteries their capacity is important. If they are too small they will not be able to handle the on-demand current of large loads. If you're putting in two 3kW inverters you must be expecting some very large loads, which automatically means you would need a significantly sized battery bank to back them up with.

    Three strings of 1290 Watts for 3870 total can support a lot of battery: like 620 Amp hours @ 48 Volts.
    That would manage about 3kW load at any given time, but not 6kW (total of the two inverters). How did you come to pick two inverters?

    It is also enough battery for about 7kW hours AC @ 25% DOD. How well does that fit with your planned usage?
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  • emcc
    emcc Solar Expert Posts: 44 ✭
    #3
    Re: C n C my System

    Two inverters bcause I am not getting a 5kw or 6kw inverter here. The largest I saw was 5000VA which is 4.5kW at best. And way too expensive.
    620Ah battery means 3 strings of 4 150Ah batteries Right?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: C n C my System
    emcc wrote: »
    Two inverters bcause I am not getting a 5kw or 6kw inverter here. The largest I saw was 5000VA which is 4.5kW at best. And way too expensive.
    620Ah battery means 3 strings of 4 150Ah batteries Right?

    Nope. Three parallel strings of 150 Amp hour batteries is 450 Amp hours.
    I'm think of L16 size which are in the 300+ Amp hour range: two parallel strings would be over 600 Amp hours. I was just looking at some "no names" that were 310 and it stuck in my mind. Trojan, for example has 320 and 390 (plus others) in that size and Crown has got 305, 330, et cetera.

    I still don't see why you want/need 6kW inverter unless you've got that much in load. If it's got to be "all at once" then they'd have to be stackable. If not it can be divided up.
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  • emcc
    emcc Solar Expert Posts: 44 ✭
    #5
    Re: C n C my System

    I have 6kW Load. 18 PCs rated at 300W. Rest is reserve. No other equipments are planned at the moment to power from solar. The largest battery we available is 200Ah rated @ 12v

    So 4 in series = 200Ah @ 48V
    3 in series = 600Ah @ 48V
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: C n C my System
    emcc wrote: »
    I have 6kW Load. 18 PCs rated at 300W. Rest is reserve. No other equipments are planned at the moment to power from solar. The largest battery we available is 200Ah rated @ 12v

    So 4 in series = 200Ah @ 48V
    3 in series = 600Ah @ 48V

    Nope.
    Batteries in series: Voltage goes up, Amp hours remain the same.
    Batteries in parallel: Voltages remains the same, Amp hours go up.

    So you need to construct strings of batteries in series to get the base Amp hours @ higher Voltage:

    (-) 6 Volts @ 300 Amp hours (+)---(-) 6 Volts @ 300 Amp hours (+) = 12 Volts @ 300 Amp hours

    Then you parallel the higher Voltage strings to increase the Amp hour rating:

    (-) 12 Volts @ 300 Amp hours (+)
    (-) 12 Volts @ 300 Amp hours (+)

    = 12 Volts @ 600 Amp hours.

    I realize these are not the actual numbers you'll be dealing with; just siting as an example.
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  • emcc
    emcc Solar Expert Posts: 44 ✭
    #7
    Re: C n C my System

    Ahem.. Sorry

    200Ah batteries at 12v connected in series 4 = 200Ah @ 48V

    To get 600, 3 strings in parallel.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: C n C my System
    emcc wrote: »
    Ahem.. Sorry

    200Ah batteries at 12v connected in series 4 = 200Ah @ 48V

    To get 600, 3 strings in parallel.

    By George you've got it! :D
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  • Sun Dog
    Sun Dog Solar Expert Posts: 115 ✭✭
    #9
    Re: C n C my System

    You mention that the PCs are rated at 300W. Is this based on the power supply in each PC? You be well served to measure the actual power consumption so that you have a real number to work with. Also measure the monitors you are using. I'm guessing switching over to laptops or low power consuming PCs is not possible? No doubt there are others but the Lenovo M92P Tiny is one I am considering getting.
    http://www.lenovo.com/us/en/PDFs/intel-tiny-desktop-whitepaper.pdf
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  • emcc
    emcc Solar Expert Posts: 44 ✭
    #10
    Re: C n C my System

    We actually measured the power. With the configuration we have, at any give point of time, the power is being consumed is 300Watt more or less 20Watts. Hence 6kW syste with a PV system of around 8kW to handle any high demand for a shorter period of time.
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  • emcc
    emcc Solar Expert Posts: 44 ✭
    #11
    Re: C n C my System

    Just for my information, are the Tracer MPPT Chargers real MPPT?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: C n C my System

    Real, yes. Good?

    Like any of the inexpensive controllers they have limitations. I think one of the problems is a limitation on the charging set points. Look at the trouble this fellow is having: http://forum.solar-electric.com/showthread.php?19521-24v-solar-system-question-from-Greece!
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