XW Pro - possible to turn with grid only (no battery)?

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aj164
aj164 Solar Expert Posts: 122 ✭✭✭
in Off Grid Solar & Battery Systems #1
This is not about running with no battery.  This is about reassuring our customers that the system will, in the very least, pass grid power through when various aspects of the system have failed.  Or, more specifically, which failures may result in no output power despite the grid being available? 

More systems use lithium instead of lead-acid batteries these days.  Lithium batteries typically have their own BMS, and they can turn themselves off to prevent destroying the battery.  If the battery turns off, the XW system is flying without a battery. 

I know the XW Pro will continue to operate with no battery if the battery gets disconnected after the XW system is up and running.  We've done service calls at more than one location where the battery is OFF and the XW is running just fine.  I know these systems have run like this for days or even weeks with no issues. 

Recently, we were called out to a site where they had no power.  The grid had gone down for about 15 minutes.  When it came back on, the XW did not wake up.  Upon arrival, we found the XW system dark (no displays; no power), and the battery was off.  As soon as I turned the battery on, the XW powered up and passed grid through. 

Is there a software setting or a wiring configuration that will enable the XW to power up with grid - even if there is no battery? 

Thanks -
Adam

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,749 ✭✭✭✭✭✭
    #2
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    NO ! XW is a battery based inverter! I have been involved with it since inception in 2006.  What you wrote may be true and it is called by engineering non specified operation. It would not be bankable or reliable. The battery is part of the design in XW.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #3
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    Newer hybrid inverters often power their control processor from battery or AC input power so connect relay can be active without battery power.

    Even if inverter has ability to pass-thru AC without battery it is wise to install a bypass transfer switch around inverter in case you have an inverter failure that requires it be taken offline or removed for repair. 
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,749 ✭✭✭✭✭✭
    #4
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    You would see faults and warnings and the warranty might be up also. Even worse if it somehow tried to invert, your loads could be damaged.

    As RC said the PDP's for XW all have bypass to protect your loads for service.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #5
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    I'm with you guys on all of these points.  At the same time, I have to address customers' concerns about the overall reliability of the system.  Ironically, we may be decreasing reliability despite the customer having bought the system to provide a backup power source. 

    I'm referring to the original post, where the batteries have gone off for one reason or another, the XW is off (because it has no battery voltage), and therefore the grid cannot automatically pass through.  Sure, there is a manual bypass switch in the PDP, but one must be present to operate that switch.  It looks like the only answer is an external, automatic transfer switch. 

    I've been installing XW systems since 2008.  I've seen all kinds of cringe-worthy events that would seem certain to destroy the electronics: dead batteries, grid applied to load, nearby lightning strikes...  Yet, the XWs just won't die. 



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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,749 ✭✭✭✭✭✭
    edited January 2022 #6
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    It is very robust. Unless the XW 60 amp transfer has been damaged, it will pass thru AC from a gen or the grid on a dead battery.
    You can test this also! Turn the Battery switch off with grid present or gen running! I would do this with a low load. No need to stress the system.

    Your first post did not state how the xwp was configured. I suppose there could be a grid mode that is stopping the transfer. I would call Schneider on this as there is so much in XWP that was added for all of the new Rule21 and utility requirements.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,749 ✭✭✭✭✭✭
    #7
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    I am working on a project with Schneider and asked them as I was curious. I know this to be true for offgrid but I have never run across this with a grid tie.

    "If LBCO is reached or battery is disconnected, XW will remain in AC Pass Thru. If the grid is lost, battery is needed to restart XW."
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • GXMnow
    GXMnow Registered Users Posts: 2 ✭
    #8
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    This is my experience as well. I had a balance lead in my BMS fail, so the BMS did shut down on me. The XW-Pro stayed in pass through and we did not even notice there was a problem until I logged into to check the system status and saw the fault notice, LBCO. It took 2 days to find and fix the fault. I really thought I was in for another $300 200 amp BMS board. But it turned out to be just a bad crimp on the factory provided BMS wiring harness. It showed as both cells on either side of the bad lead were reporting zero volts. The XW did not complain any more beyond the fault notice. As soon as the BMS was fixed and turned back on, the XW-Pro returned to normal operation with no complaint. 

    Since I had that issue, I have added a second battery bank. If one BMS shuts off now, the system will still operate on just the other bank. The only issue with that is, I might not notice an offline battery bank for a while. I do typically look at the "Battery Summary" graph once a day, and I would certainly notice the charge voltage climbing twice as fast if half the batteries went offline. but I may just add a current sensor on each bank and if one bank is pulling current and one is not, I can have it trigger an alarm. 
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