Mixing old and new LiFePo4 in system?

[B.T.]

I currently have a 24v system with 4 LiFePo4 batteries in a 2s2p configuration. I am thinking of getting a 48v system. I would also like to get 4 more batteries for a 4s2p configuration. My current batteries are a bit shy of a year old with moderate use. If I get the same brand/model of batteries and make sure not to mix the old with the new series, do you expect that I will have any issues because of the age difference? Presumably the cells and BMS of all batteries would be the same, so it seems that the charge/discharge cycles would work fine. I have considered isolating one from the other with a switch, but I would rather the operation be seamless and I would not have to be present to (e.g.) charge one and then switch to charge the other. Any knowledge or experience on this subject would be appreciated, thanks.

 

[Forbisher]

It's strange that you don't mention what brand of battery that you have?

 

[B.T.]

Is that a statement or a question? Thanks for your helpful reply?

 

[Forbisher]

Is that a statement or a question? Thanks for your helpful reply?

It was both.
The brand of LFP matters when combining them.
Is the brand and Ah of your LFP a secret?
You could just ask the brand manufacturer.

 

[fafrd]

I currently have a 24v system with 4 LiFePo4 batteries in a 2s2p configuration. I am thinking of getting a 48v system. I would also like to get 4 more batteries for a 4s2p configuration. My current batteries are a bit shy of a year old with moderate use. If I get the same brand/model of batteries and make sure not to mix the old with the new series, do you expect that I will have any issues because of the age difference? Presumably the cells and BMS of all batteries would be the same, so it seems that the charge/discharge cycles would work fine. I have considered isolating one from the other with a switch, but I would rather the operation be seamless and I would not have to be present to (e.g.) charge one and then switch to charge the other. Any knowledge or experience on this subject would be appreciated, thanks.

You’ll just have overall battery capacity of your lowest-capacity cell (probably one of the older cells).

Since you have 2P, pairing up old with new cells might get average pair capacity better-aligned...