theoretical order of cell by capacity

[gotbeans]

Is there any studies/testing on this? or theories on it?

e.g. electrons move from pos to neg so should lowest capacity battery be at the negative most of the series?


I organized my many cells in order of capacity and of course these are a set of 16 that are closest together

277.622222222222​

277.830555555556​

278.144444444445​

278.244444444444​

278.511111111111​

278.511111111111​

278.533333333333​

278.833333333333​

279.183333333333​

279.283333333333​

279.311111111111​

279.416666666667​

279.583333333333​

279.588888888889​

279.6​

279.619444444444​

Here's the next series

272.338888888889​

272.888888888889​

273.75​

273.777777777778​

274.177777777778​

274.672222222222​

275.394444444445​

275.661111111111​

275.683333333333​

276.05​

276.55​

276.794444444445​

276.85​

277.1​

277.75​

277.411111111111​

I guess I'll put pos to neg and neg to pos on these and see what happens in 5-10 years?

My other 2 sets of series cells are in random orders so they can be control ones..
I don't have a million batteries to get a real test with the outliers etc though

 

[time2roll]

Not going to matter with all in series. Lowest capacity cell will determine the capacity of the set. That lowest capacity cell will trigger the BMS low voltage shut down first.

Besides I thought the negative post had all the negative charged electrons stacked up and they travelled to the positive. But then I am not sure they move that much as we get into energy and wave theories on how electricity "travels".

 

[gotbeans]

Not going to matter with all in series. Lowest capacity cell will determine the capacity of the set. That lowest capacity cell will trigger the BMS low voltage shut down first.

unrelated

Besides I thought the negative post had all the negative charged electrons stacked up and they travelled to the positive. But then I am not sure they move that much as we get into energy and wave theories on how electricity "travels".

Current flows from positive to negative and electron flows from negative to positive.
I have 4 batteries I'm arranging in different order, guess I'll see what they do in 5 years.
I know generally AA batteries in things like gameboys that used to suck your 4 batteries dry in a few hours the first ones would go bad first almost always.

 

[Spunky]

I staggered my cells high-low-high-low....
My thinking is, the active balancer would move the charge between high and lows?

 

[gotbeans]

I staggered my cells high-low-high-low....
My thinking is, the active balancer would move the charge between high and lows?

Yes.... that's exactly what an active balancer does and is supposed to do lmao
What's there to think about there?
It's best to have the closest cells in the same battery pack, so balancing is minimal

 

[Tulex]

As a person fascinated by social behavior, I love watching people make friends.

 

[Q-Dog]

I would sort the cells from lowest to highest. Then put the lowest cells in one battery and the highest cells in the other battery.

 

[gotbeans]

That's exactly what I did <__<

but with all 4 batteries

2 are randomly ordered within the packs
1 is ordered neg to pos
1 is ordered pos to neg

 

[Q-Dog]

I don't think the order matters. You just want to make it easier for the balancers to do their thing.

 

[gotbeans]

You just want to make it easier for the balancers to do their thing.

yep definitely, that's the main reason I tested them first
didn't want to put my 285amp hour with my 274 amp hour.. (that's highest/lowest)

but now I have an experiment running I'll check in 5 years.. where the 1 cell that has issues is going to throw my conclusion completely wrong since I have such a small dataset

 

[Spunky]

It's best to have the closest cells in the same battery pack, so balancing is minimal

I was going for faster.
Seems having the highest capacity at cell one and the lowest at cell 16 would cause all circuits to shuffle the difference across the pack.

 

[gotbeans]

I was going for faster.
Seems having the highest capacity at cell one and the lowest at cell 16 would cause all circuits to shuffle the difference across the pack.

When a balancer is balancing it takes the cell amps from A -> into the balancer circuitry -> to cell B
It doesn't involve the other cells

If you have say 64 cells, and 4x 16 cell batteries you'd want the 16 cells in each of those sets to be the closest together so they're balancing less often.. Ideally the cells are identical

 

[Spunky]

Here's the cell capacities on my last battery build and cell location. I'd say the cells are close in capacity, but not identical. 301.832 ~ 301.573 (as listed on EVE factory spread sheet). On 1st charge the passive PACE BMS balancer got them to 180mV ∆ at 56V pack charge, 4A Neey took about 30mins to achieve near 5mV.
Efficiency may be lost and/or the BMS could've done the job if arranged correctly?
9) 301.832
7) 301.810
11) 301.792
5) 301.735
13) 301.728
3) 301.709
15) 301.694
1) 301.668
16) 301.664
2) 301.656
14) 301.649
4) 301.643
12) 301.612
6) 301.608
10) 301.599
8) 301.573

 

[gotbeans]

yep that's a lot closer than mine are. You didn't test them yourself though? idk if I'd believe it then

 

[Spunky]

yep that's a lot closer than mine are. You didn't test them yourself though? idk if I'd believe it then

I tested a couple of them and ran a test on one of them three times (all different results). My tests varied a couple Amp hrs and were all less then the EVE test (291 ~ 294), but more than 280Ah.
I paralleled and charged the pack of 16 that had the test cells, but the others were assembled, charged and then assisted at the top with a balancer.

Ok, I'll be listening for the correct theory on cell arrangement too

 

[gotbeans]

Yea that's what I figured, few amps up and down. Well if you only have 16 they're all in the same battery so doesn't matter as much. But if you get more then it might be worth checking to see which set of 16 should go together

 

[MisterSandals]

Efficiency may be lost and/or the BMS could've done the job if arranged correctly?

If you can charge this battery, as arranged, over 3.60Vpc w/o a cell over volt, then they are pretty darn good.

I always found the weird chit alway happened on cell 1 (most) or cell 16 for some unexplained reason.

 

[gotbeans]

If you can charge this battery, as arranged, over 3.60Vpc w/o a cell over volt, then they are pretty darn good.

I always found the weird chit alway happened on cell 1 (most) or cell 16 for some unexplained reason.

Yea that's what I'm curious about, but there seems to be no physicist papers on it or whomever would study it.

Everything says in series they should "all discharge and charge the exact same" however that's not the case, and in every portable device since forever the first or last battery is 99% of the time the one that is the lowest.

 

[LakeHouse]

Everything says in series they should "all discharge and charge the exact same" however that's not the case, and in every portable device since forever the first or last battery is 99% of the time the one that is the lowest.

For me it's cell number 8 in a 16s pack, so I guess that makes me the 1% and there are 99 batteries out there with a first or last bad cell to balance things out.
Or maybe on the typical 4s battery, half of the cells are the first or last and so it seems like those are the ones that fail most often.
All cells see the same current on charge and discharge. There's no way around it; the electrons have to go through the full circuit. But each cell may convert a different amount of that current into heat via internal resistance, and so there may be some long-term difference in charge and discharge characteristics. My gut says the order of the cells doesn't really matter, but I'm inclined to trust data when it contradicts what my gut says.
So cheers to you for doing an experiment to try to advance our knowledge!

 

[gotbeans]

For me it's cell number 8 in a 16s pack, so I guess that makes me the 1% and there are 99 batteries out there with a first or last bad cell to balance things out.

Well that just sounds like that cell is the lowest one of your bunch
Like I said in my other post, after years my data is gonna be bad because 1 cell is going to act up and skew all of my data

Or maybe on the typical 4s battery, half of the cells are the first or last and so it seems like those are the ones that fail most often.
All cells see the same current on charge and discharge. There's no way around it; the electrons have to go through the full circuit. But each cell may convert a different amount of that current into heat via internal resistance, and so there may be some long-term difference in charge and discharge characteristics. My gut says the order of the cells doesn't really matter, but I'm inclined to trust data when it contradicts what my gut says.
So cheers to you for doing an experiment to try to advance our knowledge!

Yea I have internal measurements with 1khz but what I found is even me shifting wire positions or scratching the terminal a bit and probing that made it fluctuate since we're dealing with such a fine measurement.... but at least I know all of those are basically the same and no cell is total crap or anything