LiFePO4 what should be the setting on my charge controller/inverter for LBCO?

round4round4 Registered Users, Users Awaiting Email Confirmation Posts: 1
Schneideer/xantrex has a default setting of 48 volts for the LBCO. Will discharging to this voltage level hurt my LiFe PO4 Fortress battery, or reduce the life cycles? Fortress recommends 50.5 volts, but that is not an option on my equipment.

Comments

  • mcgivormcgivor Solar Expert Posts: 3,437 ✭✭✭✭✭
    Welcome to the forum.

    And welcome to the club, the LBCO is an issue I'm sure will be addressed sooner or later by Schneider as they are working in conjunction with other battery manufacturers which require a higher value. Perhaps there will be a firmware update in the near future to address this, but for now it appears 48V is the maximum. The value is still safe, what voltage dose the BMS cut off discharge? Actually I'm in the same boat but never get so low to be of concern.......yet.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mvasmvas Registered Users Posts: 382 ✭✭✭
    edited August 2019 #3
    Please, post a URL to the datasheet of the exact model battery.

    50.5 volts / 16 cells = 3.1 volts per cell = shallower but more cycles,
    48.0 volts / 16 cells = 3.0 volts per cell = deeper but fewer cycles

    Total Energy = sum of all ( kWhrs per cycle x number of cycles )

    What is the net difference in total ( sum of all ) kWhrs generated between the two depths of discharge?
    Contact Fortress and ask them exactly how this deeper discharge will affect the number of cycles and net kWhrs generated.
  • dehvdehv Registered Users Posts: 5
    Not sure about your LiFePo4 cells, but my old a123 cells can be safely discharged down to something in the neighborhood of 2v without damage (according to mfg.) when the current drops off essentially - something around 95percent discharge.
  • ElectricLoveElectricLove Registered Users Posts: 11 ✭✭
    With all LFP cells 3.0V per cell isn't really a damaging low-point, unless fortress isn't using LFP chemistry or they are being extremely particular so they can make some warranty commitments.  LFP cells are spec'd with 2.80V or 2.85V as their "0% SOC" point, reality is they still have a little juice left at that point all the way down to 2.5V, some manufacturers even throw 2.0V on a graph (A123) but if you really discharge to 2.0V per cell often it will lead to some long-term damage of the cell.  Manufacturers are all making the same batteries with very little differences between cells but each company decides how they want to manage the customer expectations and features/benefits and warranty/lifespan issues so you get a lot of variation...

    You should not worry at all that your LBCO is 48.0V, your system will hardly ever see it (unless you didn't spec it properly) and when it does it will result in approximately zero damage to the battery cells.  The BMS in your Fortress battery most likely has 2.5VPC as its low-voltage cut-off (40.0V) so at 3.0VPC (48.0V) LBCO you won't even come close to that number.

    I have toured many Lithium battery factories and have many years of experience in this field working with LFP technology.  
    Xantrex XW 4548 + Xantrex XW 6048 (10.5kW)
    Xantrex MPPT 60A x 2 + MidNite Classic MPPT 250V x 2
    Ohmmu 100Ah LiFePO4 Group 31 Batteries x 20 (25kWh)
    Sharp 170W x 27 + YingLi 230W x 16 (8.3kW)
Sign In or Register to comment.