Help me in figuring out my system

InankaInanka Registered Users Posts: 2
edited August 2017 in Solar Beginners Corner #1
Dear all,
I am not electrician, not either mechanical Engineer, but someone who has a passion for the Solar system and I have bought recently, 
1. Inverted 5000w/48v
2. MPPT Charge control 12 - 24- 48 
3. Solar Panel 300w/36v x 6pieces
4. Batteries 6pcs/12v/200ah.
Can anybody, advice me about the best way to install this system, secondly do i need more panels/Batteries/ etc.? 
I am residing the Horn Africa, Somaliland. the Sun is from 6am to 6pm.



  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Welcome to the forum Inanka.

    A 5,000 Watt (inverter) on a 48 volt battery bank is a relatively large solar power system. While somebody that is handy around the home/shop can do it--You really need to plan ahead (tools, materials) to make sure that you do not paint yourself into a corner.

    The way to design a cost effective/reliable solar power system is to start with your loads. How many Watt*Hours per day (or Amp*Hours at 48 volts per day) do you plan on using? Do you have any large loads (i.e., well pump) that need high starting surges. With this information, you can define/design your battery bank. Then specify the rest of the supporting equipment (solar array, charge controller(s), AC inverters, etc.).

    Another way is to start with something--Battery bank, solar panels, etc. that you already have (or can obtain locally for a good price), and figure out how much power/energy it can support--Then design the rest of the system in support of that key element.

    In my humble opinion, the battery bank is the "heart" of your electrical power system. The battery runs your loads (at night, during cloudy weather), and the solar panels+charge controllers are just sized to keep the battery bank "happy" and refill the batteries the next sunny day.

    In your case, you have (useful battery configuration) 4x 12 volt @ 200 AH battery bank. That is not a large bank, but can run enough electricity to make for an easier life in a cabin, or during afternoon power outages (if you have unreliable grid/utility power). So, let us start with that.

    A 48 volts @ 200 AH battery bank (your 4x batteries in series) can support around (assuming you only use 50% of the battery bank's capacity, for longer battery life, and 2 days of "no sun" storage):
    • 48 volts * 200 AH * 0.85 AC inverter eff * 1/2 days storage * 0.50 maximum discharge = 2,040 WH per day (2 day, 50% max discharge)
    • 48 volts * 200 AH * 1/20 hour discharge rate * 0.85 AC inverter eff = 408 Watt load for 5 hours per day/night for 2 days
    The above is what I would suggest would be a good off grid cabin or home.

    A ~1,000 WH per day system will supply a laptop computer, some LED lighting, a small water pump (Recreational Vehicle/Caravan), a small DC fan quite nicely.

    A 3,300 WH per day will support the above plus an energy efficient refrigerator, a clothes washer, and a well pump--Pretty close to a "near-normal" electrical existence for a full time off grid, very conservation minded off grid home.

    Your ~2,000 WH per day system is somewhere in-between the two examples above (based on your battery bank).

    Next, to keep the battery bank "happy" you need around 5% to 13% rate of charge. 5% works well for a weekend/summer cabin. 10%+ rate of charge for full time off grid (9+ months residence). For your battery bank, the suggested solar array Wattage would be:
    • 200 AH * 59 volts charging * 1/077 panel+controller deratings * 0.05 rate of charge = 766 Watt array minimum (5% rate of charge)
    • 200 AH * 59 volts charging * 1/077 panel+controller deratings * 0.10 rate of charge = 1,532 Watt array nominal (10% rate of charge)
    • 200 AH * 59 volts charging * 1/077 panel+controller deratings * 0.13 rate of charge = 1,992 Watt array "cost effective" maximum (13% rate of charge)
    And then there is the amount of power (energy) you use per day, and how many hours per day of sun you get... Using a solar calculator, we see with a fixed array (guessing your location):

    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 88° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    Jul Aug Sep Oct Nov Dec
    You get a good 5 hours of sun minimum for this region, a 2,040 Watt*Hour (AC energy) system per day would need a minimum array of:
    • 2,040 WH per day * 1/0.52 typical off grid AC solar system eff * 1/5.0 hours of sun per day minimum = 784 Watt minimum solar array (for July)
    Now--This is the back of the envelope calculation before we really have thought about any hardware. And my assumptions may be completely wrong for you needs (i.e., you are on grid and need afternoon/evening power to ride through local random blackouts for 4-8 hours a day). The assumptions on power usage would be different.

    When you start looking at a system... Details do matter. For example, you need 4x 12 volt  batteries at a time for a 48 volt battery bank. You have 6x batteries... The extra 2x batteries are not helpful unless you get more batteries or change your bank voltage to 36 or 12 volts.

    The charge controller, need to know more about it (how many amps on the output, what is the Vpanel maximum input voltage).

    For the solar panels... Need to know their Vmp and Imp ratings (Voltage maximum power, Current maximum power). A Vmp~36 volt panel cannot charge a 48 volt battery bank. You need an array of >=72 Volts Vmp-array to properly (quickly, reliably) recharge a 48 volt lead acid battery bank. And the maximum array voltage depends on the max input voltage for your MPPT charge controller (is it 100 VDC, 140-150 VDC or what?).

    Notice the "average output power" of your battery bank (20 hour discharge rate, long term off grid cabin/home). A 5,000 Watt AC inverter may be way oversized for the loads that the battery bank can support. Roughly, a flooded cell lead acid battery bank like your would support an AC load of:
    • 48 volts * 200 AH * 0.85 AC inverter eff * 1/20 hour rate = 408 Watt "nice and easy" load (10 hours to 50% discharge)
    • 48 volts * 200 AH * 0.85 AC inverter eff * 1/8 hour rate = 1,020 Watt maximum continuous load (for 3-4 hours)
    • 48 volts * 200 AH * 0.85 AC inverter eff * 1/5 hour rate = 1,632 Watt maximum load (minutes to 1 hour or so)
    • 48 volts * 200 AH * 0.85 AC inverter eff * 1/2.5 hour rate = 3,264 Watt maximum surge load (seconds to minute)
    For a 4x 12 volt @ 200 AH battery bank, somewhere around 1,000-1,600 Watt AC inverter would typically be the maximum AC inverter that bank could reliably support.

    Too large of AC inverter can waste a lot of power (just turning on the AC inverter could draw 20-40+ watts before you turned any AC loads).

    Anyway--Lots of guesses and back of the envelope calculations. Ask questions and correct my guesses--Details matter here. And we are designing a system for you--Not for me. :)

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • InankaInanka Registered Users Posts: 2
    edited August 2017 #3

    Thanks Bill, for you useful insight and valuable advice.
    regarding to your concern of my load, I will be only be using not max 3000watt load per day, my no large load items in home, except Iron, which is 1100watts, but that can also be used once may in every week or otherwise, in peak hours.

    with this design, i intend to keep at least 1000watt spare, in case for blackout the grid will be available. My deep concern, having 6 batteries of 12v/200ah, plus 6 panel of 300watt/36v, in order to obtain and maintain the quality of the battery bank. what design is the best to implement and maximizing its output?

    for your panel concern, the number of panels are 6pcs of 300wat and
    1 MPPT and Batteries 6pcs
    1 Invert of 5000watt/48v
    with the location and sun efficiency



  • mike95490mike95490 Solar Expert Posts: 8,764 ✭✭✭✭✭
    I think to get 48V DC , you need Eight, 6V batteries, or  Four, 12V batteries

    4. Batteries 6pcs/12v/200ah.  

    will not work properly

    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: ,

  • Raj174Raj174 Solar Expert Posts: 751 ✭✭✭✭
    Notice that these are 200 amp hour solar gel batteries at 10 hr. rate. Probably closer to 240AH at the 20 hr. rate.
    Could not find any charging information on them. Was this information provided with the batteries? Need maximum charging amps and recommended absorb voltage. No EQ on these so 2 panels in series should work ok. 6 panels should produce about 30 charging amps. That's a 12% rate on a single string of 4 batteries and 6% for 2 strings of 8 batteries total. From what I've heard gel batteries do not take a high charge rate.  
    Comments? Corrections?

    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 195AH LiFePO4, Kohler Pro 5.2E.
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    And a question... "...using not max 3000watt load per day...".

    There is Watts, which is a "rate" (like kilometers per hour). And there is Watt*Hours (like kilometers driven--Specifically if you drive 100 kph for 1.5 hours, you will drive 150 kilometers).

    So--Is your load 3,000 Watt*Hours per day? Or is it a maximum of 3,000 Watts (and how many hours per day)?

    Once we better understand your energy needs, we can make better suggestions for your battery bank (i.e., 4x or 8x batteries in series strings of 4 each). And with the known loads and battery bank configuration, we can configure the array.

    In general, GEL batteries do support very high discharge rates (better than flooded cell). But the ability to discharge a GEL battery to zero charge in 1 hour is generally not great (not very useful) for an off grid/solar home. GEL batteries (at least those in the US) tend to accept only low charging current of ~5% rate of charge.

    However, it may be possible that this brand/model of battery will accept higher charging currents (and higher charging voltages than the GEL batteries in the US). I did not find a manual, but here is a link with some basic information:

    Here is a 2 page specification for a "similar" GEL battery... It appears that the charging voltage is similar (and relatively high for a GEL battery) for cycling. You should ask your battery supplier for more details (manual) so you can follow the manufacture's instructions.

    Another question--Are you looking to save money with using solar energy? Or are you looking to ride through local power outages? Will you have/need a backup genset?

    In general, it is difficult to save money with off grid solar power if you have utility power available. Between the initial costs for hardware/electronics/battery bank/solar array/etc... And that you may need to replace the battery bank every 3-5 years (or more often)--Sometimes it is just better to pay for utility power and just size the battery bank for a few hours of backup power (and use a genset if longer periods of backup are needed).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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