LifePO4 Gobel PC200 16S 280Ah Standard, cell 9 always higher or running lower?

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4711austria asked Apr 18, '24

LifePO4 Gobel PC200 16S 280Ah Standard, cell 9 always higher or running lower?

Hi,

would like to get the point, what is the cause for that behavior.

Cell 9 (no fuse, all busbars on 5Nm, nothing to see inside the pack) is a runner

1) low voltage, always running behind
2) getting charges, starts running higher as all other cells
3) on getting full, voltage is getting lower, running down (only the balancer stops that)

Normaly the balancer kicks in on 3,45V, that is not the daily voltage (3,375-3,4).

1) morning, the power is needed, cell voltage is the lowest

2) during charging, the voltage is higher

3) on getting full, the volatge starts running down (until the balancer kicks in)

- is it a cell with higher/lower cap?
- faulty cell?
- normal behavior on other gupe?

Thx!

lifepo

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Answer 1 · 2024-04-18T05:14:28Z

Alexandra answered · Apr 18 at 05:14 AM

@4711Austria

This is battery related question not a Victron question, but anyway.

Internal resistance both in the cells (and connections to and from) and bms balancing (triggering and tolerance) is the answer.

Then there is ohms law. So in charge outer cells rise faster and drop faster in discharge.

You could always rebuild the pack (rearrange cells) and see if you can change the behaviour.

If it is always one cell in particular then it just has different ESR. Could be faulty could just be different. Cant tell over the internet.

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Answer 2 · 2024-04-18T09:12:04Z

4711austria answered · Apr 18 at 09:12 AM

thx for answer, what is ESR?

I measured all resistances on the busbar (cannot reach the pole), they are all the same

arranging would be test, but means complete demount of the pack.

what I really want to figure out is, is it of concern or just a behavior I can ignore during the cell diff voltage does not rise more ?

2

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Alex Pescaru commented · Apr 18 at 10:41 AM

It's a term specific to capacitors - equivalent series resistance, but can be used when describing the internal resistance of the battery.

See https://en.wikipedia.org/wiki/Internal_resistance

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4711austria Alex Pescaru commented · Apr 18 at 02:07 PM

cells should be matched from Gobel in this pack, just one is running

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