barry said:
What i did to check the pack
Charge pack up to 4.1 volt disconnect all the cells and wait for a few days to check for SD, No SD"s
Check for dead/heaters cells, all good
Did IR check all 25 milli ohm
Check for broken fuses, All good
Check for bad connection buspars, All good
@barry,
All 25m??
Are these all the same cells from the same manufacturer? I don't mean to be questioning your measurements but I have yet to find 2 cells that have the same IR readings let alone 56 of them from different manufacturers (I'mgoing by the picture of the packfrom
here)
Of what I can tell you have a mix ofLG (LGDBMG11865), (Samsung)INR18650-29E,(Panasonic) NCR or CGR18650XXand a Sanyo of some kind in the mix.
It does appear that you are mixing high drain and low drain chemistries in a rather small 56p pack.
Again I do not want to question your IR testing results but I do find it peculiar that all these cells have an IR of 25m?.
Now if you meant a max difference of 25m? between the lowest and highest I can go with that.
Question:Is the cell ratio pretty much the same in all your packs?
The only thing I can think of is that the pack in question has a higher percentage of some cell that is causing it to drop more than the others.
Also a few days to check for SD. Takes a bit longer than that for a SD to show up esp if it is a slow leaker. My minimum rest period is 25 days and I like to stretch it to 30 to 40 days. I then wont use a cell in my powerwall with a drop of more than 0.05V.
OffGridInTheCity said:
I bought some 4 cell 18650 holders and popped in some cells. Then used alligator clips to temporarily attach the extra cells to the pack that was falling behind.
This will expand up to 0.05v or 0.06v as it reaches 4.0v/cell and then back to 0.03v max difference as it goes back to 3.5v.
@OffGridInTheCity
I think the 4 cell holder with alligator clips is a brilliant idea to chase down an underperforming pack.
As you know I built my packs with a bunch of specific criteria in mind IR being one of the paramount measurements along with SOH.
It is interesting to see that your voltage per pack deviation is exactly the reverse of mine as my cells reach ?3.4V the max difference between cells is 0.06V and when my pack reaches ?4.0V the deviation is negligible maybe occasionally 0.01V but mostly straight across the board.
This is my batrium system today slightly cloudy and the AC is running.
As you can see past midnight my bank was depleted to ? 3.45V and the variation is obvious but as the system was being charged the packs started to come closer together and at ?3.8V there is only a 0.02V difference which disappears as I get closer to 4V. Peculiar that our packs run in exact opposites.
Wolf
yes my cells are 25/26
m? it took me 1,5 year to harvest all the cells (14s60p) andall themeasurements were taken with a YR1030 andallfrom the same e-bike brand make and model (LG/SAMSUNG/PANASONIC 85% off the packs) it took me a long time to get them exept the sanyo