Recommend a LiFePo4 charge controller?

Fingers
Fingers Registered Users Posts: 19 ✭✭
in Off Grid Solar & Battery Systems #1
Can anyone recommend a lifepo4 charge controller?

It's an odd thing, there seems to be a lot of lifepo4 batteries, but I have only seen one specific lifepo4 controller, and it looks like a steaming pile.   
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,634 admin
    #2
    What voltage/AH rating of Li Ion battery bank? (link to cells/batteries?)

    What size (solar array) are you aiming at for your array?

    Does your Li Ion battery bank have a BMS (battery management system) too? What are the details of BMS (link to battery/bms will probably help).

    There are different methods of inverterfacing to Li Ion batteries... There is the "dumb" method. Just make sure your charge controller does not exceed the charging voltage for your bank/bms requirements (having a low voltage shutdown for AC inverter and/or warning alarm to avoid "killing" your Li Ion bank is good too).

    Newer/more sophisticated BMS can have "protection". Ranges from some sort of alarm to a High/Low voltage cutoff switch (to protect battery bank) to active communications between BMS and Solar Charger (larger/more expensive battery systems generally).

    My two cents--If you have a BMS with "battery cutoff"--You do not want your system to routinely/randomly hit high/low voltage limits and trigger the battery cutoff switch. For various reasons, cutting battery bank connection to battery bus will cause issues with the rest of your DC system (solar chargers can over voltage/shutdown without battery, cause damage to loads, "confuse/damage" charge controller). The BMS battery cutoff should be an "emergency shutdown" use only--Your Charging (and discharging) should never hit those hard Li Ion limits in normal operation.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Fingers
    Fingers Registered Users Posts: 19 ✭✭
    #3
    48 volt system. 8x 200aH batteries with bms. 
    About 2 kilowatt of solar panels, south. Maybe a further 1.5 to 2 kw in another array, east (I'm still not sure how to use 2 arrays for one battery bank). I haven't got those panels or batteries yet, just using 1kw of grid tie for now.


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  • Horsefly
    Horsefly Registered Users Posts: 476 ✭✭✭✭
    #4
    I think the reason you don't find many solar charge controllers that are specific to LiFePO4 is because it generally isn't required. Just set the bulk / absorption voltage to a bit less than 3.5V per cell, the absorption time to something really short (15 minutes is fine), and if you can set the tail current, set it to 1 or 2 amps.  LiFePO4 cells don't need a float, but you can use one to harvest solar for loads while the battery is full. Just set the float to something like 3.3V/cell or 3.35V/cell.

    The voltage ranges on LiFePO4 are very picky compared to lead acid, so you can't really trust that the voltage setting on the SCC is right. You'll need to measure the voltage at your battery and may have to make some adjustments.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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  • Fingers
    Fingers Registered Users Posts: 19 ✭✭
    edited January 2022 #5
    Horsefly said:
    Just set the bulk / absorption voltage to a bit less than 3.5V per cell, the absorption time to something really short (15 minutes is fine), and if you can set the tail current, set it to 1 or 2 amps. Just set the float to something like 3.3V/cell or 3.35V/cell.

    Thanks for your reply.
    How do I do this, at the charge controller, or is this something the bms does via blue tooth?

    I have old and cheap charge controllers but nothing fancy, so I'm unsure of how the new expensive kit operates.

    I have been looking at the Epever 50 and 60amp, would you recommend one?
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  • Jades
    Jades Registered Users Posts: 42 ✭✭
    #6
    Renogy and Victron are all comptible with Lifepo.
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