Hey everyone, I’m mid way through swapping an original Lacroix nazare over to 18s using the internals I bought second hand from someone parting a supersport. The battery is in, powers up without issue, but the BMS is constantly fluctuating the voltage on a few cells from 1-2V up to 6V.
Anyone seen something similar or have any ideas?
It seems very much like a loose/faulty balance connection. I’d be checking where the wires plug into the battery pcbs and possibly adding some hot glue as strain relief if that works
I just went and rechecked all the connectors and the pins appear to be fully seated, and on the Any pressing them one way or another doesn’t seem to fix it either.
One thing I forgot to mention initially was when I got the parts one of the BMS side wires had popped out of the connector. I just took a guess which slot it went in, but now I’m second guessing myself seeing the BMS PCB has 0-20 labeled. Any chance this could be related?
That could definitely be your problem.
Should be easy enough to trace the wires to their corresponding packs and ensure they are in the right spots
I have had the odd fluctuating value when using llt bms externally on a couple of boards.
Jiggle of the external balance plug normally sorts it, so I think it’s from balance wiring shenanigans. Pre wired small connectors maybe playing up a bit.
So I double checked the pinouts, using the order of closest pack 1-6, middle pack 1-6, etc as 1-18 on the BMS, 0 is pinned to negative on the closest pack
It appears to have fixed the constant fluctuation, although now it’s reading 6v on one cell and .5 on another. Any chance something else might still be off or am I just screwed now by the guy that sold me everything?
Although I just realized when unplugging the battery side connector it’s still reporting values for those cells. My somewhat limited knowledge would assume those should just read as 0when unplugged right?
Your best bet at this point would be to manually check the voltages on the balance plug at the bms end with a multimeter
I had the same issue recently. Checked all the cell groups and balance wiring. Nothing was out of place, turned out it was a damaged BMS. Replaced that and the battery works perfectly.
My advice.
Check all balance wire connections.
Check cell group voltages.
If possible, install a new BMS and see if the issue continues.
I had this happen to a LLT bms I had a few years ago. Eventually the BMS just shit the bed after 3 months of it doing this.
My advise would be to order one now and let the slow boat from china get it to you for cheap so you are not scrambling for a replacement if it does fail.
Also keep an eye on it and make sure it does not try to drain one of your cell groups to 0v. I caught my faulty one trying to do that after I had stored my board for the winter. It would take a while, but could happen.
I believe it is the BMS. Manually probing each group I have one at 3.6, but the rest hovering around 4. Sadly no spares so I guess I’m stuck on some lower power boards for awhile 
This BMS was apparently bad from the factory too since I got it new second hand
If thats the case and you have used the battery, you might need more than a new BMS…
Should balance out once I get the BMS un-overvoltage locked right?
If you have used them in that state, there is a good chance it was drained too far.
I haven’t used them at all yet. Not sure what the guy before me did, but it sounds like it was only used for a bit then sat around untouched for awhile.
Yeah, I looked up some photos of new listing and those weren’t bridged. Since they are, should my pinout on the BMS connector side only one pin per dual there? I’m using 1-18, but if that’s normal maybe I should use 1-12, 15-18, 20
1-13* apparently can’t edit yet
That was actually it! Swapped those pins around, and it looks like it’s reading exactly what I was seeing manually probing.
Hopefully this cell balances out now without issues, but at least I’m making progress
After leaving it plugged in for a day it doesn’t look like it’s actually even balancing that group. If I discharge the battery a bit them plug it in, it’ll charge with the rest, but once the rest hit max everything stops. When it’s in it’s balance phase it also doesn’t indicate that group is balancing
