Minimum charging current for 50AH 12V LiFePo4 battery?

I'm looking at building a modest solar battery-backup system based on:

100W flexible Renogy solar panel

12V / 50Ah Renogy LiFePo4 battery

Rover Li 20A Renogy MPPT charge controller

What is the MINIMUM safe long-term charging current for a 50AH / 12V LiFePo4 battery?

The 100W panel is rated for about 5.3A under ideal conditions which would be 0.1C, but in winter / cloudy conditions the 100W-rated panel might put out only 0.5 to 1A for extended periods.

Is it OK to charge a 50AH / 12V LiFePo4 battery at only 0.01 to 0.02C for extended periods?

(For example, days to weeks during extended bad weather in the winter months?)

  • I don't believe there is a minimum. depending on usage, you may need to stop or limit usage to prevent over discharg as very low charge rates may result in nearly nil usable charge. 

  • I called Renogy tech support & asked them this same question --

    They said that there's no issue with trickle-charging at very low currents, per se. For example they've heard of a customer using a 30-watt solar panel with a 100 AH battery for a computer-network backup power supply without any problems.

    It basically comes down to "amount of charge going in" vs "amount of charge being consumed", keeping those balanced. If (due to too-low charging current) the battery gets over-discharged, in the case of the Renogy LiFePo4 batteries, the BMS (battery management system) will activate, physically disconnecting the internal LiFePo4 cells from the external battery terminals until a proper charge-up cycle can be completed.

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