How to Setup Off Grid Solar System for Home Use

peacemakerpeacemaker Registered Users Posts: 2
Dear Experts,

I need to install a off grid solar system. I am not much aware about this product. I would appreciate if any one guide me regarding load calculation, battery capacity, charger controller, charger regulator, Inverter (theoretically and practically).

Load Calculation: 3 x 75 Watts Fan 220 AC Volts (15 hours), 3 x 24 Watts Energy Savor 220 AC Volts (8 hours)

Region: Karachi, Pakistan (Summers: Day time 12 to 14 hours with 35 to 40 Degree Temperature)
(Winter: Day time 08 to 10 Hours with 10 to 30 Degree Temperature)


Kashif Usman


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: How to Setup Off Grid Solar System for Home Use

    Welcome to the forum Kashif.

    Based on your information, here's is what you're looking at supplying:

    Three 75 Watt fans is 225 Watts. Over 15 hours that's 3,375 Watt hours. Already that's quite a bit of power.

    Three 24 Watt 'energy saver' (? lights) is 72 Watts. Over 8 hours that's 576 Watt hours.

    Total: 3951 Watt hours daily.

    This would be a 48 Volt system for best results.
    Converted to DC you get 4648 Watt hours, plus the inverter consumption of probably 300 more so you can call it 5kW hours DC. If you are lucky the battery bank would need to supply 4.8 kW hours, the rest coming from the panels during the day.

    That means the battery bank would be (4800 Watt hours / 48 Volts nominal) 100 Amp hours * 4 (to limit the Depth Of Discharge to 25% average) or 400 Amp hours @ 48 Volts.

    The next part is what batteries you have available to you where you are; you have to come close to that specification and they need to be real deep cycle batteries for best results.

    Where I am it would be sixteen GC2's which are pretty cheap for the power given. Wired as two parallel strings of eight giving 440 Amp hours @ 48 Volts.

    The battery bank must be determined before the solar for recharging them can be worked out. Using the above battery bank the solar would then be based on 44 Amps peak current @ 48 Volts: 2112 Watts plus the efficiency factor of 77% = 2743 Watt array, adjusted +/- to suit available panels.

    Your long daylight hours will work for you: probably 6 hours of direct sun available. You could see 8 kW hours AC from that size array in such a long day. Better to have too much than too little.

    Your high ambient temperatures will work against you: PV Voltage will be lower than expected due to higher than normal operating temperature losses. This needs to be factored in when configuring the array, and can only be done when the panels are chosen which will depend on what is available to you there.

    The same goes for the charge controller and inverter: we can give approximate specifications but you may not have the equipment available we do so the final choice will depend on what you can get. Clearly the controller should be an MPPT type and capable of >50 Amps @ 48 Volts (such as an Outback FM60). The inverter needs to be 48 Volt input, able to handle the 300 Watts output load (no trouble there as most 48 Volt inverters will be very high capacity), and have the Voltage and frequency to match power systems there (I think you have European spec 230 VAC 50 Hz power in fact).

    Anyway, that's a start.
  • peacemakerpeacemaker Registered Users Posts: 2
    Re: How to Setup Off Grid Solar System for Home Use

    Thanks for Detailed Reply.....
  • mike95490mike95490 Solar Expert Posts: 8,763 ✭✭✭✭✭
    Re: How to Setup Off Grid Solar System for Home Use

    Also, remember, with each power plant, you need a plant engineer. Someone to check water levels in the batteries, make sure things are working right, and that the generator starts properly (in case of cloudy weather, if you drain the batteries to 0, you destroy them)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

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