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REC-BMS / Sunny Island not charging

  • H
    I installed the REC-BMS some time ago. Recently, I wanted to add two additional battery strings, necessitating a change in configuration to a master with three slaves from a single REC Q BMS. This took some time to prepare, but before I flashed a bunch of firmware. This would take down my critical load. To deal with a prolonged outage on my critical load, my electrician installed a transfer switch where the output of the SI could be replaced with grid power allowing me to take the SI offline without a critical load impact.
     
    By the time, I was ready to make all the changes, the current battery pack has discharged down to 10%. When I connected the power to the SI along with the REC Q BMS, the pack started charging. The pack charged as expected, stopping at around 90% capacity. All good to this point.
     
    The battery is now down to 46% and yet the charger is not starting. What perplexes me is: Why isn't the SI charging the batteries? 
    • Is the BMS not asking for charge current?
    • Is the SI ignoring the request for charge current?
    The SI is talking with the BMS. If it wasn't the SI shuts down, I've been there. The SOC shown on the SI matches the SOC from the REC BMS display showing the SI and the BMS are successfully communicating with each other in real time. In the SI architecture, the BMS asks for current and the SI complies.
     
    Here is the REC-BMS configuraiton:
     
    "cmin":2.8,"cmax":3.7,"tmax":55,"bvol":3.58,"bmin":3.45,
    "tbal":55,"tmin":-10,"capa":280,"char":3.65,"ioff":0,"chis":0.25,"razl":0.25,
    "maxh":0.25,"minh":0.1,"bmth":5,"ioja":0.019531,"soch":0.05,"chac":0.6,"dchc":1.5,
    "maxc":70,"maxd":100,"clow":2.95,"socs":0.466269,"cycl":10,"chem":3,"sisn":2,
    "cfvc":0.8,"err":{"p":0,"num":0},"nnc":{"bms":1,"cell":2},"vnc":{"bms":1,"cell":5},
    "toor":{"bms":1,"cell":3},"baud":{"lcd":56000,"com":56000},
    "bms_name":"1Q-4702","addr":32,"tunit":1,
    "Ah":149,"cur":-0.986328,"new_log_every_midnight":true,"out":false}
     
     
    Here is a screenshot from my system right now.
     
    Current Home Page
     Thoughts?
     
    Thanks,
     
    Hank
     
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  • R

    Hey Fred, we don't currently have an SMA demo set up here.  Do you have any ideas for this gentleman?

    Thanks, Rick

    @Fred Egelston 

  • H

    Is there a method to determine what the REC Q BMS has requested of the Sunny Island 5048U?

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  • F

    Hi Hank,


    Sorry for the delayed reply. Are you still having issues? I have a few systems setup SMA and REC products.

     

    What is your incoming source of electrons? Are you DC coupled with a charge controller or do you use string inverters with your Sunny island? 

     

    Do you see the Lithium BMS charge flash on the display screen on the sunny islands?

     

    Thanks,

     

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  • F

    Also your SOC calculation may be incorrect, to me it appears your SOC should be greater than 60% assuming you are using lifepo4 chemistries 

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  • H

    Fred,

    No problems. I finally figured out what was wrong. I don't  know how the parameter changed on the SMA, but we changed the start parameter from null to auto and then to start which did the trick. The SMA started charging and the pack has reached 95%.

    I will post the exact solution when I get back next week. 

    Hank

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  • F

    Hi Hank,

    I am happy to hear you reached resolution. I am very interested in more details, as you know these SMA can be querky if parameters are off. Let me know if you have any other issues.


    Thanks,

    Fred

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