I've been trying to design a circuit to charge LiFePO4 batteries, I tried with smth small like a 300mA constant current at first and it charges fine. But when charging reaches 3.4V, the voltage of the battery starts increasing rapidly.... I've tried different chargers but get the same response .... How would this be dealt with? Maximum voltage of the LiFePO4 is 3.6V
I heard that LiFePO4 batteries can be charged to 4.2V safely...... but it's sort of risky as it might damage the life of the cell...
any ideas?

 

Lifepo4 cells have to be charged in Two stages, first stage is Constant current upto 3.65V, then Constant voltage, there are deadicated chip chargers that can do this without all the hassle.


https://www.powerstream.com/LLLF.htm

 

Lifepo4 cells have to be charged in Two stages, first stage is Constant current upto 3.65V, then Constant voltage, there are deadicated chip chargers that can do this without all the hassle.


https://www.powerstream.com/LLLF.htm

Yes, I'm aware of that... but the voltage gets very jumpy after reaching 3.4V... is that normal otherwise how do they get it to reach a steady 3.65V... in order to start the constant voltage charging?
I had already read the article you sent actually, it doesn't answer my question but a very good article none the less.
and a dedicated chip might or might now work... I have one and it's somewhat reliable not the best..
but I would like to understand what's happening, if anybody could help that would be great!!

 

he voltage gets very jumpy after reaching 3.4V.

How jumpy is "jumpy"?

I would just change the charger to constant voltage once it "jumps" to 3.65V.

Here's a CC/CV circuit using an LM317 that may be of interest.
Its constant-current value and CC/CV crossover voltage could be adjusted to your needs.

 

How jumpy is "jumpy"?

I would just change the charger to constant voltage once it "jumps" to 3.65V.

Here's a CC/CV circuit using an LM317 that may be of interest.
Its constant-current value and CC/CV crossover voltage could be adjusted to your needs.

Thank you sir, actually my circuit also implements an LM317, but not nearly as complex as yours I'll take a look at it.
Well, jumpy as in jumps from 3.4V to 3.7 in like 20 seconds!! it's really harmful especially to Lithium batteries

 

actually my circuit also implements an LM317, but not nearly as complex as yours

Part of the complexity is so that once it reaches the maximum CC voltage, it permanently switches to the lower voltage CV mode.
It can only go back to the CC mode by being deliberately reset.