How to keep NiFe Batteries Charged?

midijeepmidijeep Registered Users Posts: 77 ✭✭
I have a bank to 40 NiFe 200Ah batteries.  I only use 38 due to my solar setup.  I keep rotating two batteries but would like to at least keep a charge on the two 1.2 V NiFe batteries that I am not using.  The manual states to fully charge the battery needs 1.7 Volts. I just want to keep them charged (1.2V - 1,7v) so I don't have to keep rotating them in and out.  The other option, which I don't want to do is remove the electrolyte.
What equipment would you recommend to "trickle charge" the two 1.2v NiFe batteries e.g. solar panel with charge controller, battery charger, etc...... .
Thanks in advance!


  • Raj174Raj174 Solar Expert Posts: 557 ✭✭✭✭
    edited March 13 #2
    It might be possible to use a LiFePO4 charger on 2 cells in series. I read, the maximum charge voltage is 1.8V per cell, so 2 in series would be 3.6V. The LFP charger is 3.65V. I don't know for sure if the 5 mV over recommended voltage would be a problem, if not, maybe a charge current of about 3% or 6 amps would be enough to keep them in a charged state. NiFe are not that efficient so it may take a little more current. Just an educated guess.

    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH HI Power LiFePO4 no BMS, 4000W gen.
  • mike95490mike95490 Solar Expert Posts: 7,505 ✭✭✭✭
    I went the route with a charger that has programmable set points and can use all cells. TristarMPPT-60
    But it looks like the LFP charger, applied 1x a week, would keep the 2 cells in  shape.  Too much voltage just boils off a bit more water
    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

    gen: ,

  • BB.BB. Super Moderators Posts: 27,133 admin
    For your stored cells... You generally want them to be somewhere around 1/2 charged (around 3.0 volts for typcial LFP... As always check the specifications)... Keeping them at 100% state of charge will age them pretty fast (lose significant capacity in 1-2 years).

    Also, the cells need to be disconnected from any loads or Battery Management Systems. If you cannot disconnect the loads, then you will need to check/recharge occasionally.

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