LiFePO4 cells in use since 2020. Bloating? Capacity?

[upnorthandpersonal]

As some of you may know, I'm in the process of moving my batteries into a new enclosure. Reasons: it's more organized, space is better optimized, and I can add more batteries more easily later if needed. This is the first time I took these apart since I built them somewhere early 2020. I bought the cells (LF280N) in 2019, and they have a manufacturing date in 2018, so 5 year old cells. These were bough from Haomi (long gone seller) and definitely not EV grade.

Here they are, still in their fixture with the BMS removed. That's right: no spacers between the cells, and my DIY flexible bus bars in all their glory



No bloating what so ever - and this battery was 100% full:



Didn't want to remove all bus bars, so only took of the positive terminal side where the BMS connects to while moving cells.


















































I did a quick capacity test (no graph on this device) while I was taking the other pack apart and putting it back together in the new enclosure: 267Ah. I have no idea how many cycles I have on these batteries, but considering that these are 5 years old, have been running the house for the past three years and counting, and cost me 100 Euro per cell shipped, I call that a win.

 

[houseofancients]

you did well, but it also confirms what we've been seeing in age tested cells ..

do show the new enclosures when done

 

[SparkyJJO]

So approx 1% capacity loss per year on average. I wonder if it has been linear or not.

 

[upnorthandpersonal]

I really wish I had time to do a proper capacity test - take that 267Ah as lower limit. It was also the oldest cell of the batch and one that could be considered a runner.

 

[upnorthandpersonal]

do show the new enclosures when done

I might. Once all the rest around it is 'presentable' as well

 

[upnorthandpersonal]

So approx 1% capacity loss per year on average. I wonder if it has been linear or not.

Definitely not linear:

ShieldSquare Captcha

As always, temperature has the biggest impact.

 

[fafrd]

As some of you may know, I'm in the process of moving my batteries into a new enclosure. Reasons: it's more organized, space is better optimized, and I can add more batteries more easily later if needed. This is the first time I took these apart since I built them somewhere early 2020. I bought the cells (LF280N) in 2019, and they have a manufacturing date in 2018, so 5 year old cells. These were bough from Haomi (long gone seller) and definitely not EV grade.

Here they are, still in their fixture with the BMS removed. That's right: no spacers between the cells, and my DIY flexible bus bars in all their glory

View attachment 147058

No bloating what so ever - and this battery was 100% full:

View attachment 147059

Didn't want to remove all bus bars, so only took of the positive terminal side where the BMS connects to while moving cells.

View attachment 147060
















































I did a quick capacity test (no graph on this device) while I was taking the other pack apart and putting it back together in the new enclosure: 267Ah. I have no idea how many cycles I have on these batteries, but considering that these are 5 years old, have been running the house for the past three years and counting, and cost me 100 Euro per cell shipped, I call that a win.

Had you capacity tested when you first got your cells? Over the time you’ve been using them, did you ever do full charge / discharge cycles or even some lower reference like 15% to 90% to have any idea of actual % capacity loss since the cells were first broken in?

 

[upnorthandpersonal]

Had you capacity tested when you first got your cells? Over the time you’ve been using them, did you ever do full charge / discharge cycles or even some lower reference like 15% to 90% to have any idea of actual % capacity loss since the cells were first broken in?

Not really. I've done so with other cells in the past, but these just had to get to work. I tend not to go below 3V per cell, but in summer do go to 3.55V per cell on a regular basis. Not in winter though. It's very hard to come up with any numbers when these cells are supposed to power the house 24/7. I hadn't even looked at them (as in, physically opened the box) until yesterday.

 

[upnorthandpersonal]

That said, I do consider this to be a real world case where the cells are not in a controlled situation: going without being fully charged for half a year, being fully charged often during the other half. Sometimes sitting at negative temperatures when we're not present during winter, but never really at anything over 30C. And of course, various loads and different states of discharge throughout the year.