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LV6548 and BMS connected Pylon compatible option #5

errcl65

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Jul 16, 2022
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The batteries are new Jakiper 48V 5U with the same BMS as SOK and Jakiper PRO. So I think
the problem presented is general to all the PACE-IC BMS P16S100A.

With BMS coms enabled and working, the master LV gets is battery parameters #6, 27, 29.

The problem I am having is the values for charge and float are too high, both are at 57.6V.

This charging voltage is causing a severe top balancing issues on some of the packs.
I see 300 to 400 mV difference in the cells near the end of the charge cycle. Some
cells are peaking over the 3.9V cut-off which fault the entire pack out of service.

The BMS has a very slow reacting balance bleed which kicks in (Balance Threshold) at 3.5V during charge.
But this does little to slow the eventual over voltage build up, especially when there is a sizeable
charge current coming in.

If left disconnected, the OV cells settle down. I assume the pack will re-connect its output when
the OV cells falls below the OVP Release (3.45V).

Is the solution to use USER and manually pick a good charge and float which will keep the cells
from over volting on charge?

How reasonable is it to assume that 16 cells will remained reasonably balanced over
time?
 
The batteries are new Jakiper 48V 5U with the same BMS as SOK and Jakiper PRO. So I think the problem presented is general to all the PACE-IC BMS P16S100A.

With BMS coms enabled and working, the master LV gets is battery parameters #6, 27, 29.

The problem I am having is the values for charge and float are too high, both are at 57.6V.

Ugh. So silly.

This charging voltage is causing a severe top balancing issues on some of the packs. I see 300 to 400 mV difference in the cells near the end of the charge cycle. Some cells are peaking over the 3.9V cut-off which fault the entire pack out of service.

Keeping the batteries @ 57.6V will actually encourage more BMS balancing. It looks like a shit show, but it should eventually correct.

The BMS has a very slow reacting balance bleed which kicks in (Balance Threshold) at 3.5V during charge. But this does little to slow the eventual over voltage build up, especially when there is a sizeable charge current coming in.

Yep, but over time it will get there.

If left disconnected, the OV cells settle down. I assume the pack will re-connect its output when the OV cells falls below the OVP Release (3.45V).

Typical behavior. Even notably imbalanced cells will settle to negligible voltage difference in the working range.

Is the solution to use USER and manually pick a good charge and float which will keep the cells from over volting on charge?

It's a viable approach. Set absorption to as high as possible to no push a cell past about 3.6-3.7 and set float to 3.45V/cell.

How reasonable is it to assume that 16 cells will remained reasonably balanced over time?

Once balanced, daily cycling with balancing active during charge can generally maintain the top balance of healthy cells.

If they sit for as little as a few days to a couple weeks, you may note that the imbalance returns.
 
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