Finally System is done

Zakarume
Zakarume Solar Expert Posts: 143 ✭✭
My system is done. Last Night i drain the batteries down to a 75% SOC by what the Midnite Kid said along with Whizbang Jr. Today had full sun and it charge my bateries to full. What i would now like to do is add more to my system

1. Have 4 6v batteries in series for a 24v system (225AH).

2.Would like to add 4 more 6v batteries (8 total @450AH) PLUS

3. Take the 4 -100 watt panels i did have and reinstall in series/parellel for 24v and get a PWM Charge Controller for the extra charging of the 8 batteries.

Will this work at charging the 8 6v bateries at 450AH?
1460 Watts Solar @24v. 675 AH Battery Bank using 12 6v Trojan T-105. 1 Midnite Classic 150. 1500 Watt 24v Samlex Pure Sine Inverter

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Finally System is done

    Total Wattage--Assuming 5% to 13% rate of charge:
    • 450 AH * 29 volts charging * 1/0.77 rate of charge * 0.05 rate of charge = 843 Watt array minimum
    • 450 AH * 29 volts charging * 1/0.77 rate of charge * 0.10 rate of charge = 1,695 Watt array nominal
    • 450 AH * 29 volts charging * 1/0.77 rate of charge * 0.13 rate of charge = 2,203 Watt array "cost effective maximum"
    You want to add 2x the battery bank and 400 Watt array to the existing:
    • 960 Watt array + 400 Watt additional = 1,360 Watt array
    You would be at:
    • 1,360 Watt array / 1,695 Watt array (10%) = 0.8 or ~8% of battery capacity
    That is a decent size array... But this depends on how you plan on using your power and how much.

    If your daily power needs are mostly during the night--And, of course, you don't draw too much power, you should be fine.

    If, however, you have significant power needs during the day (irrigation, office equipment, etc.) full time--Then you should look at your average wattage requirements for the loads--I.e., you want a 5% minimum into the battery bank + enough solar panels to support the loads (especially if this is a full time off grid system as opposed to backup/seasonal/weekend system).

    Using PV Watts for Springfield Mo, 37 degree tilt from horizontal, fixed array:




    Month
    Solar Radiation
    (kWh/m2/day)


    1
    3.93


    2
    4.20


    3
    5.18


    4
    5.54


    5
    5.71


    6
    5.80


    7
    5.92


    8
    5.99


    9
    5.44


    10
    4.95


    11
    3.83


    12
    3.29


    Year
    4.99




    Toss the bottom three months (as needing backup genset or simply reducing power needs during poor weather):
    • 1,360 Watt array * 4.2 Hours of Sun average per day (February) * 0.52 end to end system eff = 2,970 Watt*Hours per day of 120 VAC power
    And, if your 100 watt panels have Vmp in the rang of ~17.5 to 18.6 volts or so, then two panels in series with two parallel strings connected to a PWM solar charge controller on a 24 volt battery bank should be fine.

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