12v batteries/48v solar array?

alright71alright71 Registered Users Posts: 15
Quick question...some of you know my situation, some don't. I live in a very remote part of DRC without utilities. Here we have to make things work...even though it may not be ideal.

One group here has a 48v outback FX inverter, Outback 60 CC, 4 North Star 170 batteries and 12-12v panels. One of the batteries is dying a long slow death and is killing the other batteries. as it is a 48v system, with 4 12v batteries the system will no longer function once that battery is removed.

Does anyone see a problem if i take the inverter out of service, remove the dying battery, wire the batt array for 12v and use a small, 12v inverter until the batt array can be replaced? I would also change the set points on the CC for 12v settings but would leave the PV array at 48v.

Anyone see any issues?

thank you!

Blake

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: 12v batteries/48v solar array?
    alright71 wrote: »
    Does anyone see a problem if i take the inverter out of service, remove the dying battery, wire the batt array for 12v and use a small, 12v inverter until the batt array can be replaced? I would also change the set points on the CC for 12v settings but would leave the PV array at 48v.

    Depending on the rating of your smaller inverter you may be drawing more current (between battery and inverter) than your fuses and wiring can handle.

    Same concerns apply to the wiring between charge controller and battery. You may have four times the current running between the controller and the battery.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • alright71alright71 Registered Users Posts: 15
    Re: 12v batteries/48v solar array?

    Yes, i can see your point...thankfully the small inverter is just 500 watts connected directly to the battery bank.
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: 12v batteries/48v solar array?

    The only other comment would be the size of the array--The MPPT Outback controller can only manage about ~1/4 the amount of power with 12 vdc output vs 48 volt output (still 60 amp maximum at 12 or 48 volts -- P=V*I).

    Otherwise, the MPPT controller will be fine. It will safely/reliably limit its maximum output current to ~60 amps.

    The maximum "cost effective array" at 12 volts and 60 amps would be:

    60 amps * 14.5 volts charging * 1/0.77 panel+controller derating = ~1,130 Watt array 'cost effective' maximum

    So--if you have a larger array for the 48 volt system, you will find that the amount of solar power you can draw from the system at 12 volts reduced.

    You need to also check the wiring from the controller to the battery bank to make sure it can handle the maximum current (60 amps) at 12 volts (if it was sized for a smaller 48 volt array before). You can reprogram the MPPT CC with a Mate for less current if wiring is not available.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 12v batteries/48v solar array?

    You don't need the MATE to program the charge controller.
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