LiFePO4 does not need a multistage charging profile.
The manufacturer of our 100 ah cells, and the MFG of the common 280ah cells specifies charging at a rate of 0.5c up to a maximum voltage limit of 3.650 per cell.
Based on the LiFePo4 charge curve the cells will reach nearly 100% charge at 3.500v per cell, so this is our recommended target voltage (14.0v per 4-cell battery, 28v per 8 cell battery).
Note that there is no mention of “float” charging. This is only applicable to lead acid yet most charger designs include a float setting for LiFePo4, usually 13.2v for a 4 cell battery.
Why is this a problem? Because at 13.2v the battery will be significantly discharged, and so you will observe the battery going through a deep cycle after every full charge, even though it remains plugged into shore power.
Therefore the ideal charger for LiFePo4 batteries (in our opinion) is a current limited power supply set to 14.0 to 14.2 volts.
6 thoughts on “How to charge LiFePo4”
Does C rate of charge matter other than how long it takes to charge? I have a 16S/48V setup with 280Ah batteries, and it is not easy to charge at 0.5C, which is 140A. Is there an issue if my C rate of charge is, say 0.1 or less? I haven’t any panels yet and I’m using a power supply. Your BMS is also just 100A. Must I charge them in groups of 12 volt or 24 volt? Thanks for any help.
A slower charge rate is always acceptable. The quoted C-rate is the upper limit.
You will need a charger for a 48v system. The upper limit voltage should be set to 56.8v.
Generally a charger will stop charging at .05C (5%). That would be 14 Amps for a 280Ah battery. What happens if my solar panels are only charging @3-5 amps, won’t this overcharge the battery?
Do you mean “under charge” the battery?
Since you said the charger would stop at 14 Amps and then you stated your panels only produce 3-5 Amps. Since 3-5 is less that 14, wouldn’t that mean the charger would not charge… “Generally a charger will stop charging at .05C (5%)”
Thanks, just learning this stuff and a bit confused
I was previously going to set my BMS to 3.55 volts for the 60280 LiFePo cells i purchased from BH. i read this and was curious as to the possible differences
When should the charge be terminated? i.e. when would I be finished charging? Let’s make this concrete: suppose I use a CC CV charger and set it to the 14.0v that you recommend and start the charging process. Do I let it run until the charge current is effectively zero, or do I cut off the charging process at some other point? If so, what point? i.e. what is the charge termination criteria?