Any disadvantage to treating a 32 cell battery as 16 pairs in parallel?

[D. Abineri]

If I pair up my 32 cells with a parallel connection on each pair and connect all the pairs in series to get 48 V and use my 16 cell capable bms, is there any disadvantage to doing this? What if half are 200Ah and half are 320Ah, what would be the best way to create this connection?
Thanks for any comments on this issue.

 

[BentleyJ]

If the cells are not the same capacity, it makes more sense to build 2 separate batteries. Each with their own BMS then connect the batteries in parallel.

 

[timselectric]

is there any disadvantage to doing this?

Need fuses between each pair.
Still limited by the max current rating of the single BMS.
Lose the redundancy of having two batteries.
Lose the monitoring of individual cells.
No way of knowing if a single cell is going bad.

 

[D. Abineri]

If the cells are not the same capacity, it makes more sense to build 2 separate batteries. Each with their own BMS then connect the batteries in parallel.

Thanks

 

[D. Abineri]

Need fuses between each pair.
Still limited by the max current rating of the single BMS.
Lose the redundancy of having two batteries.
Lose the monitoring of individual cells.
No way of knowing if a single cell is going bad.

Thanks, Tim.

 

[Nobodybusiness]

If I pair up my 32 cells with a parallel connection on each pair and connect all the pairs in series to get 48 V and use my 16 cell capable bms, is there any disadvantage to doing this? What if half are 200Ah and half are 320Ah, what would be the best way to create this connection?
Thanks for any comments on this issue.

You really have no idea if any of your parallel cells are bad.

Drawing more current from 1 battery vs 2.

Lose redundancy.

Just a few I thought about.

 

[D. Abineri]

You really have no idea if any of your parallel cells are bad.

Drawing more current from 1 battery vs 2.

Lose redundancy.

Just a few I thought about.

Thanks

 

[wpns]

I used to think you couldn’t tell if one cell was going bad in a parallel pair, but then I realized that that pair would be a runner, would either charge too fast or run out of capacity early, and would show as that one cell pair being horribly unbalanced compared to the rest of the battery.

Fuses would be impractical, you would need matched fuses at the battery voltage, and the BMS current feeding into individual busbars between the cell pairs, and it would get really ugly really quickly. I don’t know how likely it is that one cell would short and the other cell would dump enough current into it to blow something up or catch on fire, but I seem to think I’ve seen commercial batteries built with cells in parallel pairs.

 

[timselectric]

seem to think I’ve seen commercial batteries built with cells in parallel pairs.

And they are all individually fused.
Even the EV batteries with hundreds of 18650 cells, have fuse links at each cell.

 

[D. Abineri]

I used to think you couldn’t tell if one cell was going bad in a parallel pair, but then I realized that that pair would be a runner, would either charge too fast or run out of capacity early, and would show as that one cell pair being horribly unbalanced compared to the rest of the battery.

Fuses would be impractical, you would need matched fuses at the battery voltage, and the BMS current feeding into individual busbars between the cell pairs, and it would get really ugly really quickly. I don’t know how likely it is that one cell would short and the other cell would dump enough current into it to blow something up or catch on fire, but I seem to think I’ve seen commercial batteries built with cells in parallel pairs.

Thanks, very good points