Possible BMS Issue?

tjurgensentjurgensen Registered Users Posts: 2
I am just putting together my first system with two 24v 8s BYD batteries, connected in parallel, from techdirect. These came with preprogrammed chinese BMS's: Better Shenzhen Better New Energy BT.25M2020-MWJ115152. I had previously connected these to my step down converter and ran some 12v appliances/lights w/o a hitch. Today I was ready to connect my solar through my EPever Tracer 10415AN cc, had all four leads connected, battery plugged in with the breaker turned off, and the solar isolator switch in what I mistakenly thought to be the off position. After making the PV connections on the roof I see the cc on and after about 10 sec. I realized it shouldn't have been and quickly flipped the breaker, connecting the batteries. The cc was indicating all was well but after a few more seconds the warning light appeared and showed there was no battery connection so I disconnected the solar. Now the batteries show ~26v (what they were @ before) until they're connected to any sort of load: cc, or converter after which I read a volt or two. I attempted to make the PV connections again this time in the correct order and got the same ~10 sec. of green status until it switched to show no battery connection. When connecting the cc w/o PV, the screen flashes on for a split second before going back to blank. I have also tried jumping the b- and p- on the BMS to possibly reset but to no avail. Does anyone have a clue as to what issues I could be running into? Any help/suggestions are much appreciated.
Thanks for reading,


  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Disconnect all loads then unplug the sense wire connector from the BMS then reconnect, this should restore the BMS.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • tjurgensentjurgensen Registered Users Posts: 2
    Thank you this was a big help. Here is an update to my situation. https://diysolarforum.com/threads/possible-bms-issue.22220/#post-262438
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