Overdischarge protection using SMA Sunny Island

Hi all there, hopefully there are somebody can help me.
I have an off-grid system with SMA Sunny Island 5048, SMC 8.0, 42 Evergreen panels @205Wp, 1 bank battery Suneom 48V 600Ah.
By utilizing parameters setting in the Sunny Island, we try to protect the battery at SOC 50%, as follow :
- ExtSrc = PVOnly, GdSocEna = Enable
- BatPro1Soc = 60%, BatPro2Soc = 55%, BatPro3Soc = 50%
When the battery capacity reach 50%, the Sunny Island turned off automatically. But when it goes up again manually, the battery capacity info shown in the Sunny Island display is 21%.. It mean when it goes off, the battery keep drained from 50% to 21%. How can we overcome this ?
Anybody experiencing similar thing? Thanks.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,523 admin
    Re: Overdischarge protection using SMA Sunny Island

    I am sorry I cannot help you with the setup... But some questions.

    Do you think the system shut down at 50% state of charge?

    When the battery was showing 21% on the Sunny Island, was the battery discharged from 50% to 21% (somehow) during that time?

    Or was the 21% a false reading?

    Did you try measuring the battery Specific Gravity during this time for an indication of state of charge?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Overdischarge protection using SMA Sunny Island
    psidharta wrote: »
    Hi all there, hopefully there are somebody can help me.
    When the battery capacity reach 50%, the Sunny Island turned off automatically. But when it goes up again manually, the battery capacity info shown in the Sunny Island display is 21%.. It mean when it goes off, the battery keep drained from 50% to 21%. How can we overcome this ?
    Anybody experiencing similar thing? Thanks.

    I am sure that Stephendv, our experienced and very helpful SMA poster, will be by to help.

    But first, to clarify: When you say that "it goes up again manually" do you mean "when the Sunny Island turns itself on 'manually,'" or when YOU as a user turn the Sunny Island back on manually.

    Stephen was just helping me with a friend's Sunny system and he said:

    One of the problems with AC coupling is that the sunny island is the only way to charge the batteries, so if it shuts down completely because of low SoC, and then the next day there is full sun, the batteries won't charge unless someone physically goes and resets it. So be very careful about what you set that final SoC limit to.

    Perhaps you are expecting the system to restart itself in order to start charging the batteries again, when it cant??

    Anyway, my "stab" at an answer.:cool:
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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