Cell 2 about .150 over the others at top of Charge cycle

[Watch Me Build]

So I built a 4 cell 280ah LifePo4 with the eve cells I got from dongguan lighting. While I still had a house, and electricity I had done the top balancing with a 10a charger. And I did it 3 days in a row until the cells rested at 3.5v. then I drained them to 3.3ish and packed them into the bus.

I moved a week later, and it took another 9 days to get the solar components hooked up. (Mppsolar 1012 aio, DGJBD bms, 600w panels.)

Now when it charges the cell #2 is peaking out faster than the other 3 at the end of the bulk cycle. By about .150 v.... they all settle back down after a bit of rest and are within .015 or so.

So is this a huge issue? Will it correct itself over time hopefully? Or is my only course of action to top balance again, which is going to be nearly impossible since I'm 100% off-grid.

Here are some screenshots.

 

[snoobler]

Not ideal, but not a big concern.

Ensure you have the balancing set to only occur during charge, 30mA deviation and above 3.3V.

It will take awhile, but it will equalize with regular cycling.

If you had balancing active at all times, balancing during discharge or idle can actually un-top balance them.

EDIT: to ensure it's performing as intended and moving in the right direction, consider keeping a daily log of the balance process trying to capture your peak voltages. Also a good idea to log your low voltage before charging occurs in the morning.

You should see the top end converging and no change or slight divergence at the low end.

 

[Watch Me Build]

Not ideal, but not a big concern.

Ensure you have the balancing set to only occur during charge, 30mA deviation and above 3.3V.

It will take awhile, but it will equalize with regular cycling.

If you had balancing active at all times, balancing during discharge or idle can actually un-top balance them.

EDIT: to ensure it's performing as intended and moving in the right direction, consider keeping a daily log of the balance process trying to capture your peak voltages. Also a good idea to log your low voltage before charging occurs in the morning.

You should see the top end converging and no change or slight divergence at the low end.

I'm not sure if I can set it to only occur during charge. Do you have experience with overkill solar/DGJBD bms and know where the setting is?

Here's a screenshot of the setting. I had it at 3.2 and a deviation of .015... So I updated it. Look right?

 

[snoobler]

https://github.com/FurTrader/OverkillSolarBMS/raw/master/Overkill_Solar_BMS_Instruction_Manual.pdf

 

[MisterSandals]

I moved a week later, and it took another 9 days to get the solar components hooked up.

Did you disassemble the battery and reassemble with cells in a different order?

Or did any of the bus bar connections become loose during the move?

 

[Watch Me Build]

Did you disassemble the battery and reassemble with cells in a different order?

Or did any of the bus bar connections become loose during the move?

Nope. I marked each cell, and reattached them 1 through 4.

They were unhooked and wrapped back in their foam cocoons for the move. I put the pack back together the same way I had it on the counter top at my old place except this time securing it with hose clamps and end blocks.

 

[Watch Me Build]

https://github.com/FurTrader/OverkillSolarBMS/raw/master/Overkill_Solar_BMS_Instruction_Manual.pdf

View attachment 25211

Yes I see that, but have no idea where to enable or disable it... I'm on the android bluetooth app.

Possibly this?


Where it says charge balance?

That's the closest thing I can find to that parameter. And that's under the "function setting" menu in the app. There's nothing under parameter view and parameter setting.

I believe it is only doing it while charging though because I don't see the green "B" icon near the cells in cell view otherwise.

These are my cells now after resting for a bit.

 

[snoobler]

Might be the difference between the iphone and android apps.

The 3rd decimal hurts my brain, so I just round to .XX. You have 3.32 to 3.33, which is great. Unfortunately, you may see divergence at full charge until it gets fully top balanced. Daily discharges with charges to full will help.

 

[Denis]

So I built a 4 cell 280ah LifePo4 with the eve cells I got from dongguan lighting. While I still had a house, and electricity I had done the top balancing with a 10a charger. And I did it 3 days in a row until the cells rested at 3.5v. then I drained them to 3.3ish and packed them into the bus.

I moved a week later, and it took another 9 days to get the solar components hooked up. (Mppsolar 1012 aio, DGJBD bms, 600w panels.)

Now when it charges the cell #2 is peaking out faster than the other 3 at the end of the bulk cycle. By about .150 v.... they all settle back down after a bit of rest and are within .015 or so.

So is this a huge issue? Will it correct itself over time hopefully? Or is my only course of action to top balance again, which is going to be nearly impossible since I'm 100% off-grid.

Here are some screenshots.
View attachment 25197View attachment 25199

So I built a 4 cell 280ah LifePo4 with the eve cells I got from dongguan lighting. While I still had a house, and electricity I had done the top balancing with a 10a charger. And I did it 3 days in a row until the cells rested at 3.5v. then I drained them to 3.3ish and packed them into the bus.

I moved a week later, and it took another 9 days to get the solar components hooked up. (Mppsolar 1012 aio, DGJBD bms, 600w panels.)

Now when it charges the cell #2 is peaking out faster than the other 3 at the end of the bulk cycle. By about .150 v.... they all settle back down after a bit of rest and are within .015 or so.

So is this a huge issue? Will it correct itself over time hopefully? Or is my only course of action to top balance again, which is going to be nearly impossible since I'm 100% off-grid.

Here are some screenshots.
View attachment 25197View attachment 25199

I have two banks of 16 cells parallel 280ah without a bms, but I did add an active balancer on each bank that I can monitor with my phone.
Since adding the balancer I've noticed that not all cells are equal in some form or another.
Capacity, resistance and chemical reactions within are not all the same for each cells.
All my cells are grade A, to a point, but not all cells are.
They vary in voltage while being charged, I've noticed up to .150v or 150mv, and my cells are balanced.
With that kind of fluctuations between cells, a bms would always be triggered.
I control charge bulk at 56.8 volts, and this one cell has reached 3.62v while the others are around 3.53v and some a bit lower.
And as soon that I apply a heavy load on the bank, that same cell is at the lowest of the bank.

I thought for sure I had a bad cell, so I contacted Amy at Xuba, and she replied back that they had heard of the same problem and the solution was to change the cell place with another.

So I did, I took cell number 16 and swap it with #1, and voilà no more problem. Now my cells are all the same within.005v most of the time and don't need to balance.

So maybe if you try to swap cells with another, would work out.
I've done this swap about 40 days ago and everything is still very good.

 

[snoobler]

Denis, your description is different from the OP's.

Assuming you have good connections everywhere, your example of a cell being BOTH the high voltage and the low voltage indicates one or both of the following:

1. Reduced capacity
2. High internal resistance

 

[Denis]

Denis, your description is different from the OP's.

Assuming you have good connections everywhere, your example of a cell being BOTH the high voltage and the low voltage indicates one or both of the following:

1. Reduced capacity
2. High internal resistance

Yes connection are good and tight, capacity is the same as the other cells and also the resistance check is the same. And yes the swap of cells were recommended by Xuba and the battery pack test is without any issues now.

 

[Mtour]

You might be surprised how small of a difference in capacity there is from for a 150mv at the top and bottom of the charge curve... I bet your talking less the 5ah, if that..

 

[Watch Me Build]

Hmmm. Strange. Although I don't believe we are having the same issues. Mine is only at the very top of the charge range. But good info for when I set up my other 16 cells into a 48v configuration.

 

[Craig]

Denis, your description is different from the OP's.

Assuming you have good connections everywhere, your example of a cell being BOTH the high voltage and the low voltage indicates one or both of the following:

1. Reduced capacity
2. High internal resistance

or it indicates some sort of bad connection which I am willing to bet was resolved when he swapped cells around.