Battery Upgrade

nickdearing88
nickdearing88 Registered Users Posts: 100 ✭✭✭
I finally took the plunge and purchased 2 - 12v 100Ah LiFePO4 batteries from Battleborn (via our hosts).

Per the manufacturer's recommendations, I wired the batteries in parallel (12v 200Ah) and charged to ~14.4v with a 30 minute absorb. I set the CC to 14.3 because the meter usually reads the battery voltage a few tenths of a volt lower than actual.

The balancing system is passive (using resistors) and top-balances between 14.2v and 14.6v (max). Battleborn has had really good luck with cell balancing using only the passive system and it saves costs, lowers self-consumption, and complexity.

I then switched to series configuration for 24v 100Ah. I've only played around for the past two days but I'm watching charge and discharge voltages very closely. It's amazing how flat the discharge curve is compared to LA. The OC resting voltage when full is about 13.6v so I set my float voltage at 13.5. Therefore no real charging should occur during float unless a large load turns on. It even took several amp-hours of use after completing absorb before the batteries dropped from absorb voltage to my float setting!

I plan to cycle between 20% - 90% SOC but I figured a full absorb was important for balance purposes during commissioning.

I'll update with my experience as I go, but so far -- I'm happy.
Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter

Comments

  • karrak
    karrak Solar Expert Posts: 326 ✭✭✭✭
    I had a look at the documentation on your battery, looks like a nice battery. I really liked to see the spec saying the battery lifespan in Ah cycled through it rather than in number of cycles!

    It is a shame that the battery doesn't have a way that you can measure the individual cell voltages.

    I agree with your strategy of charging to 14.4 during the commissioning. On a regular basis I would charge a battery like yours to 27.6V (3.45V/cell) and terminate the charge at C/20-C/50 or set the absorb time at 15 minutes and set the float to 26.8V (3.35V/cell), slightly less than your setting.

    Once a month I would do a charge and absorb at 28.8V (3.6V/cell) to balance the battery. If you wanted to automate this process and if your charge controller will allow it you could set the charge controller to do an equilise cycle  at 28.8V (14.4V/cell)

    Simon

    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Is there any information regarding ambient  temperature verses life expectancy? Can't seem to find any on the Battle Born site.
    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.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    edited July 2017 #4
    Warning.  If you are going to top balance this battery, you better keep the EQ amps BELOW the amps the BMS / balance vampire boards can handle, or you will overvoltage some cells
     And same theory about Absorb and Float, don't push more into the cells, than the balancer boards / BMS can handle
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    karrak said:
    I had a look at the documentation on your battery, looks like a nice battery. I really liked to see the spec saying the battery lifespan in Ah cycled through it rather than in number of cycles!

    It is a shame that the battery doesn't have a way that you can measure the individual cell voltages.

    I agree with your strategy of charging to 14.4 during the commissioning. On a regular basis I would charge a battery like yours to 27.6V (3.45V/cell) and terminate the charge at C/20-C/50 or set the absorb time at 15 minutes and set the float to 26.8V (3.35V/cell), slightly less than your setting.

    Once a month I would do a charge and absorb at 28.8V (3.6V/cell) to balance the battery. If you wanted to automate this process and if your charge controller will allow it you could set the charge controller to do an equilise cycle  at 28.8V (14.4V/cell)

    Simon

    @karrak Thanks for the great suggestions. I agree and was thinking along the same line with your suggested voltages and absorb time. Once of the reasons I went this route is to test and experiment. Once I'm more comfortable with the LI characteristics, I would likely make my own "pack" with prismatic cells and a custom BMS/active balancer. But these are very practical for a drop-in LA replacement and perfect for users who don't have a detailed battery background.

    Great idea about the equalization voltage for balancing, I never thought of that but it's perfect!
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    mcgivor said:
    Is there any information regarding ambient  temperature verses life expectancy? Can't seem to find any on the Battle Born site.
    I didn't see it on their website either but they might if you email them. Mine will be in a temperature controlled environment in a few weeks but are currently wired up in the garage. I'm targeting to keep them between 60F - 75F, which should keep them very happy.
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    Update: I did run into a BMS issue but as soon as I mentioned it to Battleborn, they knew exactly what it was. Apparently they discovered a small number of BMS units had an issue and I just happened to get one of them. They are promptly sending me two new batteries with correct BMS system and pre-paid return labels. The customer support seems to be awesome.

    During specific discharge parameters (after 20 minutes, between 25-50 amps), the BMS would cut the voltage to 9.5v for a second, then back to normal. Under 25 amps or over 50 amps discharge, the issue doesn't occur.
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    Here are is the discharge curve chart from Battle Born if anyone's interested.
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    mike95490 said:
    Warning.  If you are going to top balance this battery, you better keep the EQ amps BELOW the amps the BMS / balance vampire boards can handle, or you will overvoltage some cells
     And same theory about Absorb and Float, don't push more into the cells, than the balancer boards / BMS can handle
    Shouldn't be a problem......so far they're down to only about .02C by the time they are anywhere near the Absorb voltage.
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • karrak
    karrak Solar Expert Posts: 326 ✭✭✭✭
    Once I'm more comfortable with the LI characteristics, I would likely make my own "pack" with prismatic cells and a custom BMS/active balancer.
    When you say active balancer, do you mean a balancer that shifts energy from one cell to another?

    Personally, I can't see much point in doing this as the amount of energy that is lost in just passively balancing using resistors is negligible. In the last twelve months I haven't had to balance my battery at all, in the twelve months before that I would have wasted about ~10Wh to balance my battery. I also can't see much point in having automatic balancing unless you want a "set and forget" system or it is operated by someone who didn't have enough technical expertise to do the balancing manually.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • karrak
    karrak Solar Expert Posts: 326 ✭✭✭✭
    mike95490 said:
    Warning.  If you are going to top balance this battery, you better keep the EQ amps BELOW the amps the BMS / balance vampire boards can handle, or you will overvoltage some cells
     And same theory about Absorb and Float, don't push more into the cells, than the balancer boards / BMS can handle
    Shouldn't be a problem......so far they're down to only about .02C by the time they are anywhere near the Absorb voltage.
    On top of this, if any cell did go outside the safe operating voltage zone the battery BMS would disconnect the battery from the rest of the world regardless of how much current was being taken from or put into the battery.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    karrak said:
    Once I'm more comfortable with the LI characteristics, I would likely make my own "pack" with prismatic cells and a custom BMS/active balancer.
    When you say active balancer, do you mean a balancer that shifts energy from one cell to another?

    Personally, I can't see much point in doing this as the amount of energy that is lost in just passively balancing using resistors is negligible. In the last twelve months I haven't had to balance my battery at all, in the twelve months before that I would have wasted about ~10Wh to balance my battery. I also can't see much point in having automatic balancing unless you want a "set and forget" system or it is operated by someone who didn't have enough technical expertise to do the balancing manually.

    Simon
    Yes, I did mean moving current from one cell to another to balance.
     
    Good to know. I'm still learning the nuances of various balancing. When I first looked at Battle Born's information, I read "Automatic Cell Balancing" and interpreted as "Active Cell Balancing". When he said it was a passive system with resistors, I figured it was a cost savings measure. By the sounds of it, your system is also using resistors for balancing? I just figured most of the systems people installed used active balancing to move the current between cells rather than eat it up via a resistor as heat. But, I was expecting large imbalances based on some posts here.

    Another +1 on your lower Absorb rate and using Equalize monthly at 3.6v/cell for balancing. Really good idea and although it's only been a few days, seems to be working great!
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter
  • nickdearing88
    nickdearing88 Registered Users Posts: 100 ✭✭✭
    karrak said:
    mike95490 said:
    Warning.  If you are going to top balance this battery, you better keep the EQ amps BELOW the amps the BMS / balance vampire boards can handle, or you will overvoltage some cells
     And same theory about Absorb and Float, don't push more into the cells, than the balancer boards / BMS can handle
    Shouldn't be a problem......so far they're down to only about .02C by the time they are anywhere near the Absorb voltage.
    On top of this, if any cell did go outside the safe operating voltage zone the battery BMS would disconnect the battery from the rest of the world regardless of how much current was being taken from or put into the battery.

    Simon
    Absolutely, that's the purpose of the BMS, to protect the battery.
    Current system: 8-100w Renogy panels mono/poly, 2 strings of 4 panels in series - 24v 100Ah AGM Battleborn LiFePO4 batteries - Morningstar MPPT40 CC - 1500W Samlex PSW inverter