Unusual solar power problem

oldandslowoldandslow Registered Users Posts: 2

Greetings,

I recently ordered a prewired setup from Wholesale Solar which included two 24volt 220ah Discover lithium ion batteries for $7,100. They were shipped to me in Montana where I have an off-grid cabin. Each has an integral computer called a Battery Management System (BMS). I unboxed the batteries and hit the power button to turn them on. No problem. Next I hit the power button to turn off the BMS but it would not turn off no matter how long or short the time I pressed the power button.

I contacted WS multiple times by email and they said it had never happened before. Their suggestions were--# 1. keep pressing on the power button and maybe it will turn off and #2- download a program to my laptop and then to the BMS and maybe that would work.

I told them that option #1.didn't work and that option #2 had some problems for me. First I shouldn't have to reprogram two brand new and never hooked up batteries with the "hope" that it would fix them and also that my lawyer said any self-reprogramming would muddy the waters for any warranty claim. I asked for service by a field-tech or to have the option of returning the new batteries for repair. WS said that this wasn't covered by the Discover warranty and it was my responsability to fix them.

So this means that by the next time I visit my cabin (it's a 7,000 mile trip each way) my latest high-tech Li batteries will have self discharged themselves to a permanently damaged state.

So my questions to the group are-- 1. Has any else had this problem with Discover batteries? and-- 2. Any suggestions on resolving this issue with Wholesale Solar?

best wishes- Don

Comments

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭

    Can describe the prewired system, usually LFP batteries are shipped in a partial state of charge, needing a charging source, be it solar or other means, to bring them up to a fully charged state. The purpose of the BMS is to protect the batteries from overcharge, over discharge, short circuit, temperature, overload and so forth. The notion that BMS itself caused damage to the batteries themselves seems highly unlikely, it's sole purpose is to protect, theroritically speaking.

    As far as problems with Discovery batteries themselves, I've no comment, how to deal with the vendor would involve how the batteries were installed, charging voltages, charging current values etcetera , nothing so far has addressed these questions, which the vendor will surely ask.

    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.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭

    Don Discover has been excellent me and my customers. This forum/windsun store is in competition with Wholesale Solar so I would say you really should have bought them here.

    So, start a claim with Discover. Forget about the people you bought this from for now. Also keep in mind that cold temperatures will kill LFP and Montana has them. If the battery is not on it will not log temperature. If it was on, it would.

    Good Luck

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • oldandslowoldandslow Registered Users Posts: 2
    Thanks for the input.
    Mcgivor-  I believe it is a Battery Management System problem and not a battery problem.  However having the BMS turned on will discharge the batteries to such a low state of charge that they will become permanently damaged (if I understand correctly).  So the problem was how to turn off the BMS on each battery.

    Dave- good to know that Discover has good customer service.  I may have to contact them directly after I return to my cabin in late summer.  I also understand that cold temps damage Lithium ion batteries but it has never been charged or discharged at any temperature-- only taken out of the shipping boxes and powered "on."  It has not been stored below the -4 degree F temps recommended by the manufacturer.
    I also was unaware that Wholesale Solar was a competitor of this forum.  My mistake and apologies.

    I checked the voltage of the two batteries before I left and they were both at 26.4 volts.  I don't know what state of charge that signifies.

    So it looks like my only plan is to see how the batteries are in late summer when I return to the cabin.  If permanently damaged they are of no further use and I'll try to hook up my system to run daytime power to the well pump and storage tank and forego replacing another battery bank.  If the batteries are still rechargable I can try to download a repair program onto my laptop and then to the BMS to reset the system as recommended by WS and Discover.  Seems like a lot of trouble for two very expensive, brand new and never used batteries.

    best wishes-  Don
     




  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    My understanding is one of the primary functions of a BMS is to prevent damaging overdischarges, not cause them.  IMHO, the BMS should also prevent charging/discharging in temps outside viable range, and the BMS itself should have a very low idle self-consumption.

    Assuming 8 cells in series (24v nominal), 26.4v pack voltage would be ~3.3v/cell, which seems about right for a resting lifepo cell.  Voltage isn't a great state of charge indicator AFAIK though, as voltage is pretty flat except at the very high and low ends of the SOC curve.

    FWIW...Others here with more lithium experience may differ.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    As long as you left them off you are fine. One of the first things said in the manual is to charge the battery. Good Luck
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭

    The voltage, 26.4V represents a state of charge in the 90-95% neighborhood, they have a very low self discharge, so long as there is no load they should be fine. The voltage as a state of charge is, in the case of LFP, difficult to estimate with such a low resolution, the difference between 26.400V and 26.450V can be quite significant in terms of ampere-hours, by observation, the difference between 2700V and 28.800V can be close to 2Kwh on my 400Ah bank, but for extended life expectancy it's best not to charge to 100% on a regular basis.

    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.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    I do not believe that is accurate what the OP said. The battery is hazmat # 9 and not supposed to be shipped at more than 30% Soc.
    The statement that he could not turn them off also seems weird. It is a pretty simple switch but it is a constant 30 watt load if they are on.
    I would make the 7,000 mile trip and take an Iota 24v battery charger and a genset.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    Wow, the BMS takes 30w just being on? 
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    Some do !  Iron Edison and LG. I do not know the 24V ones but the 48 volt AES is around that. I think when you get past the "night" system inverter business you have to accept the load for a home. A cabin probably is not going to leave the system on unattended.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    I had imagined a sort of arduino-like milliamp range self consumption.  720wh/day is a big enough (for me) load that it would be material in planning charging capacity etc.

    I wouldn't leave it on unattended (as I do with FLA), as partial SOC is no problem.  I'd have to rig up heat for charging, and probably wouldn't want that going on unattended anyway.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    From the specifications of my BMS 
    Current consumption ≤25uA
    Would take a long time to discharge 400Ah 
    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.
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    That's more like what I had assumed.  30w is something like a million times more?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    A million???  The Discover is also talking with the Schneider inverter, protecting from over charge, discharge currents, generating a warning for hi/lo temp and then shutting down from hi/lo temp to protect itself, and finally logging all of this for warranty.

    In large installations, only one battery is using that much during discharge, the rest are on the AES bus and probably not using much at all.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    I think a microamp is 1/1,000,000th of an amp, so 25uA wouldn't be quite a millionth of 30w, but roughly that order of magnitude.

    A rPi zero w/wifi could probably do a lot of measuring, logging, and comms, using ~120mA, ~0.7w.  An arduino could be much lower. Obviously more if heating resistors for cell balance, if non-latching relays stay energized, etc.  Maybe it's like modern software... we don't need to worry much about resource limits on modern computers, so we don't :wink:


    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Also, if it is an active BMS--It is taking energy from one part of the system to another part to equalize cell voltages. That may only happen when the battery is "charging" -- One would hope. 5 amps across an ~4 volt Li Ion cell would be 20 Watts (actively charging).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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