Over Current Protection Needed for LiFePo batter bank?

st4rgut
st4rgut Registered Users Posts: 36 ✭✭
in Off Grid Solar & Battery Systems #1
Hi, I have a 48V battery bank consisting of 4 100AH flooded lead acid deep cycle batteries in series. I am considering upgrading to LiFePo batteries since my bank appears to have degraded significantly in less than a year (voltage drops and rises too fast). My solar system produces more than 2000 Watts on a sunny day. On researching LiFePo batteries I see there is a maximum charging current of 1C for a 100AH LiFePo battery. Since my controller can output as much as 60 Amps to the battery bank, should I be worried of overcharging the LiFePo? What kind of damage could it cause if I already have a good BMS in place? I am kind of ignorant of how batteries work. Does it act like a load and only draw current that is needed or will it attempt to use all the power it's getting from the solar system?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    st4rgut said:
    Hi, I have a 48V battery bank consisting of 4 100AH flooded lead acid deep cycle batteries in series. I am considering upgrading to LiFePo batteries since my bank appears to have degraded significantly in less than a year (voltage drops and rises too fast). My solar system produces more than 2000 Watts on a sunny day. On researching LiFePo batteries I see there is a maximum charging current of 1C for a 100AH LiFePo battery. Since my controller can output as much as 60 Amps to the battery bank, should I be worried of overcharging the LiFePo? What kind of damage could it cause if I already have a good BMS in place? I am kind of ignorant of how batteries work. Does it act like a load and only draw current that is needed or will it attempt to use all the power it's getting from the solar system?
    1C would be 1/1x the battery bank capacity or 100amps... 

    Have you equalized your Flooded batteries to regain capacity? Are they "marine" batteries? In general FLA (Flooded Lead Acid) are pretty bomb proof, if you have lead calcium/Marine batteries a year is not unexpected. But if you have true deep cycle batteries, I'd try taking Specific Gravity (SG) readings and do some corrective equalizing. As apposed to maintenance equalizing.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • st4rgut
    st4rgut Registered Users Posts: 36 ✭✭
    #3
    Yes, they are marine batteries. I have 4 in series, one is almost a year, the other 3 are a few months old. 
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