Outbacks default setting for inverter shutdown is 10.5 volts...

softdown
softdown Solar Expert Posts: 3,896 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
It seems that is the default setting in the majority of inverters. Well...10.5 volts is too low in my humble opinion. Leave your batteries at 10.5-10.7 volts while you are away for awhile? Get ready to buy new batteries pretty soon.

It takes a few minutes and a surprising amount of navigation to change this setting. Opinions will vary but 11.5 volts is an arguably good shutdown point. Your batteries will quickly bounce back to 11.7 volts and that is likely not in the realm of true danger.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Just remember if you want 11.5 volts at the battery, typically the wiring is designed for a 0.5 to 1.0 volt drop (12 volt -- I suggest 0.5 volt wiring harness drop for 100% rated output; 1.0 volt drop for 200% surge output power).

    Some inverters allow you to set something like 11.5 volts for 1 hour, or 10.5 volts for 2 minute before shutdown and/or generator autostart (as examples)... It helps a bit to prevent early shut downs when you have surge current (starting a well pump) vs light loads that are slowly taking the battery dead.

    Add that battery output voltage (and capacity) are voltage dependent--The automated shut down voltage set points are not great ways of "saving the battery bank"--Mostly, they were there to prevent inverter damage and AC load brown outs (low battery voltage, inverter has to compensate by drawing more current. And low DC input voltage can cause low AC output voltage).

    I am surprised at times at how well lead acid batteries actually work when there are so many ways of murdering them. Better Battery Manage Systems even for lead acid batteries would be nice--But the complexities of per cell BMS and generator autostart add for more chances of failure(s) too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    softdown wrote: »
    It seems that is the default setting in the majority of inverters. Well...10.5 volts is too low in my humble opinion. Leave your batteries at 10.5-10.7 volts while you are away for awhile? Get ready to buy new batteries pretty soon.

    It takes a few minutes and a surprising amount of navigation to change this setting. Opinions will vary but 11.5 volts is an arguably good shutdown point. Your batteries will quickly bounce back to 11.7 volts and that is likely not in the realm of true danger.

    It will depend on your load and even type and size of your battery bank.

    I can see 1+ volt voltage drop/sag when running above 1/15th of my battery capacity, even with a near full battery. That If I was running 50 watts vs 1500 watts, I have in essence no voltage sag. I can draw down to 10.5 volts and see a near dead battery. I thought Outback had a voltage over time cutoff? This helps start motors and such...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Photowhit wrote: »
    I thought Outback had a voltage over time cutoff?

    Outbacks do have a low voltage, based on a period of time, cutoff.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #5
    Alright...so we have a voltage over time cutoff...somewhere. I was surprised at how many steps were involved in changing the cutoff from 10.5 to 11.5. Seems that a voltage over time setting would involve even more.

    FWIW....this is a 48 volt system so an 11.5 volt setting is really 46 volts.

    To be honest, changing settings on the Outback MATE makes me uncomfortable. I have done it but prefer that my far more experienced friend change the settings. Last time I did significant work, the inverter made pulsing noises for a couple hours, and produced no power, while I sweated out finding the cause.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Yess and to be clear, I was talking 1 volt drop on a 24 volt system.... Though I have seen worse!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #7
    And keep in mind - - low voltage cutoff for many if not most inverters, is to protect the inverter from damage, not to protect the battery from over-discharge.
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #8
    Makes sense. Damaging a $3000 inverter vs ruining $3000 worth of batteries?

    Why not just set the cut off at 11.5 volts. A bit of inconvenience once in a while vs tragedy?

    I don't respond well to true tragedy. Just sit there and lick my wounds until time has done its healing.
    waynefromnscanada wrote: »
    And keep in mind - - low voltage cutoff for many if not most inverters, is to protect the inverter from damage, not to protect the battery from over-discharge.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #9
    p. 11 of the Outback Inverter Programming Manual: "A built in five minute delay eliminates nuisance FX shutdowns,"
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
    · Share on Twitter

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