Bulges on side of cells during top balance

[Gurusi]

Holy shit you basically blanched your cells, man I am sorry that happened but I can see exactly how it occurred.
A few pictures and explanation should be added to the top balancing explanation that apparently is around here somewhere.

I would rather not be made a case of!

it’s unclear to me as regard the exact cause. Perhaps because I didn’t bolt my extended bus bars together, maybe because the degree of SOC between the individual cells was too acute, maybe because I didn’t leave the pack in parallel for a period of time settling before charging, maybe a glitch with the charger.

 

[Gurusi]

There is definitely less swelling the father away from the charge point. Cells 16,15,8 and 7 are packed up for recycling.

I’m unsure about packs 1,2,3,4 they have the least swelling as they were the furthest away. Cells 9-14 have no swelling

A flat pack of 4 cells is 11” 1/4 and the four swollen is 13”

 

[Quattrohead]

Were your voltage sense cables at the opposite end to the charging cables ?
That would have done it for sure with those poor connections between cells.

And I am not saying calling you out personally, just a couple of pictures and explanation of what can go wrong if the connections are not good.

 

[Gurusi]

Were your voltage sense cables at the opposite end to the charging cables ?
That would have done it for sure with those poor connections between cells.

And I am not saying calling you out personally, just a couple of pictures and explanation of what can go wrong if the connections are not good.

Sensing cables were the next cell along.

I get it, just a joke as it is tough posting failures for all to see.

 

[featherlite]

This. How are these bus bars connected??? Looks like heat shrink is the only thing bonding them together???

Op, Say it ain't so!

 

[justgary]

LiFePO4 “charged” status is a combination of voltage and current. ie: if you reach 3.65V at 0.05C current the cell is 100% charged. If you approach 3.65V at a lower current, or hold a lower voltage for a longer time, you can overcharge the cell.

This. 0.05C cutoff for a 280Ah cell is 14 Amps, not 1 Amp.

 

[Nobodybusiness]

Hey, just in the process of a 16S. 280ah top balance. Using the ZKEEBCA 40 L. They are Configured in parallel and a under compression.

I had previously been using the cells with the inverters but found imbalance at the higher range of 3.4v when charging via the charge controllers

I noticed a spike in voltage on the test software at about 3.35 V. And when examining the cells I noticed bulges in the first two cells so have stopped the balance. I’m unsure what the cause is or how I should proceed….

Have I done something wrong in the process? Is it too much compression?

Edit added better cell bulge photos

If you really wanted to do your busbars that way, I’m sure Weber would make ones long enough for you.

Otherwise probably not a good idea to use shrink wrap.

 

[hwse]

Underway discharging now. Charge settings were 3.65V C-CV, 40amps with a cutoff current of 1.amp.

I noticed the bulged end of the cells where my charger was hooked up was warm and noticeably cooler the other end.

Cells are compressed based on lots of reading on the forum and are variable for give (spring system). I can’t recall my spring in-lb settings right now!

I’m hoping I haven’t damaged them. but don’t know how to move forward. I could top balance each cell individually I guess

You said "where my charger was hooked up." Does that mean that the + & - connections were both to the same cell? If so, given that you were charging with 40A, you likely had significant voltage drop from the charge end to the non-charge end. where did you have the voltage probes for the tester? if it was not in the first cell nearest the charge connection it if very likely that you went over the 3.65v on that cell.

 

[bogi]

@WindWizard in #8 you've mentioned active balancer. Could you tell me which one you are using? Can it be used together with JKBMS?

 

[WindWizard]

With my 128 cell pack, (48 volt) the overkill solar BMS's do not have enough capacity to do the active balancing. I use two active balancers because my cells are divided into two 64 cell packs.

Amazon.com

I only top balance at the top end. I turn the active balancer's on at 55 volts and then off at 53.5 volts. It keeps the cells balanced within 10 mv. I don't do the compression and after 3 years, my cells are still looking great with no bloating.

The balancers work great with any BMS.

I run the cells up to 55.2 volts and then float them at 53.7 volts. For the low end, I run them down to 48 volts and then shut off the inverters. When charge gets up to 51.2 volts then I turn on the inverters again.

I am putting up another 12 panels making the total of 54 solar panels. The winter months are difficult to generate enough power. Last year I was short 24kwh in November, and 107kwh in December. This year I was short 191kwh in January and 19kwh in February. I am going to see how this winter goes with the extra panels and then I can be totally off grid.