LifePo4 chemistry reset myth or real?

[tonyg]

Hello fellow solar enthusiasts!
My system is working like a charm.
I charge the pack of 16 Eve lf280k to 55.2V in absorption, and they are all fairly balanced. I've never seen the delta above 0.020 V. Each cell voltage never goes above 3.5, 99% of the time stays in the 3.45V area when fully charged.

This is enough for me, and never triggered the over voltage protection and the amount of stored energy is enough for me. I consider this to be a full battery.

But I've read somewhere - I really cannot find where, sorry for not providing a link - that LiFePo4 chemistry would benefit from a reset from time to time. That is, bring the voltage of each of the cells as close as possible to 3.65 V which would be max of these cells.

Any truth in that?

 

[grizzzman]

Yes it is a fact. But it is recoverable.

 

[timselectric]

Never getting above 3.45v, doesn't give you any balancing. The delta should be very close in the flat part of the curve. Unless you have a defective cell.
You should balance your batteries at least once every 10 days. If you want to get full capacity from them.

 

[tonyg]

The balancing actually does work pretty well in my case as well, and it does start depending on how you program the BMS.

Here is a screenshot of the battery after it went through a short cycle to 100% - it is autumn now - and the bms did some balancing.

 

[tonyg]

My main question was if not bringing the Lifepo4 cells to 3.65 V has a detrimental effect on them over time.

 

[timselectric]

At 3.32v per cell, there's no way to know if your cells are balanced. You are in the flat part of the curve.
One cell could be at 40% , while another is at 70% .

My main question was if not bringing the Lifepo4 cells to 3.65 V has a detrimental effect on them over time.

3.65v is not a damaging voltage for LFP cells.
It's not recommended to go above 3.65v, to provide a safety margin.
Over voltage Damage begins at 4.2v.
But, could be lower in extreme temperatures.

 

[timselectric]

My main question was if  not bringing the Lifepo4 cells to 3.65 V has a detrimental effect on them over time.

Not detrimental
Just decreased capacity available. If you don't balance occasionally.

 

[toms]

My main question was if not bringing the Lifepo4 cells to 3.65 V has a detrimental effect on them over time.

I would say no. My cells are 12yrs old, never been over 3.5V, still cycle 300ah out of a 400ah pack.

When they fail to do this i’ll rebalance and see if it helps - you might be waiting a while to find out though.

 

[tonyg]

Here's a final video from a relevant series that does all this research for us! Andy is great:

I think this sums it up well, but you can check out the other videos for a full journey related to the discussion here.