[TUTORIAL] How to build your own LiFePO4 Replacement for a Group 24 Battery

dexter12353dexter12353 Registered Users Posts: 19 ✭✭


The only thing missing is connecting up to an inverter, but we are working on making that tutorial/guide right now.

Comments

  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited March 11 #2
    Explaining the importance of top ballancing the cells prior to assembly would be a useful addition to the tutorial, relying on the BMS to achieve ballance could take weeks or more, depending their individual SOC, this requires holding at maximum voltage for extended time.

    Typically in offgrid applications the charge voltages are set below maximum cell thresholds to improve cycle life expectancy, so ballancing would never occur, I only bring this up because this is a solar forum, EV or other grid charging really doesn't apply, although not specifically mentioned.

    Additionally accurate top ballancing is critical when assembling a large capacity prysmatic cells to create a cell block, this prevents potentially damaging cascading current to lower SOC cells, this is not applicable to series connected  single cells, but worth noting for the benifit of those who are considering building a large capacity parallel series prysmatic bank.

    This comment  is intended to be constructive, not negative, please do not misconstrue the intent. 

    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.
  • wellbuiltwellbuilt Solar Expert Posts: 636 ✭✭✭✭
    I’m headed in to my 3rd season with my golf cart battery’s and they still seam to be working 
     like new , except for one cell on one battery the sg seams to stay low 12.65 or so.
      If I’m charging them hard and giving them a lot of float time the one battery will keep up with the rest . 
      So I’ve been looking at the LiFe battery’s for my next set . 
     They sure seam expensive 
     but the video above makes it look like a regular guy could assemble a set of battery’s ? 
       Lucky for me I have a few years to figure all this out . 
     I’m in a very cold area my utility room dose stay above freezing I’ve seen some 31.5 temps 
      But in my battery box it stays warmer .
     When charging my lead acid battery’s every day they stay warm 45o 
       I have a friend looking to power up a travel trailer and he has perked my interest 
       Any thoughts
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • jtdiesel65jtdiesel65 Solar Expert Posts: 223 ✭✭✭
    mcgivor said:


    Typically in offgrid applications the charge voltages are set below maximum cell thresholds to improve cycle life expectancy, so ballancing would never occur, I only bring this up because this is a solar forum, EV or other grid charging really doesn't apply, although not specifically mentioned.


    If I read this correctly, you are saying that absorb voltage will be less than the balance set point on the BMS and so the BMS will never enter balance mode? From what I read, some BMS allow you to adjust the voltage in which balance starts. But perhaps its that no significant balance can occur at the absorb voltages.
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    With the focus on top ballancing, regardless of where the trigger point for balancing is set to start, it would be impossible to achieve top ballance if the ultimate voltage is set below the aggregate of all cells combined 3.650V value, the result would be a ballance point somewhere other than top.

    Generally speaking it's unnecessary to ballance on a regular basis, an initial ballancing before assembly is all that is required, this reduces the stress associated with doing so and results in extended life expectancy, this is explained in the manual for CALB cells.


    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.
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