I finally got to repair my board again. I was super content, and took it straight for a 5miles run. After that battery was fully empty. so i charged it. when I unplugged it i noticed the bms had shutdownmode activated. so i unscrewed everything and found that one pack was about 1.3v only. in my build i used 3dprinted modular batterypacks. i checked the pack and 3 of the cells were completely dead 0v only one had 3,5v left. all ot the other packs were at ~4.08v.
I then saw that the screw from my connecting wire the red one in the picture was lose. So now my question is, whether my bms is broke (bc it shouldnt even have come to this enormous discharging of the pack, sensor wire is all good and properly attached).
or if the loose connection can have some influence on the entire system causing those weird problems.
Every cell that went to 0V should go strait to recycling especially if it was drained for a longer period of time. DO NOT USE THEM anymore. It is a fire hazard.
If I understood correctly, there is no way for you to know if those 3 cells were dead before 5 mile ride you should assume those are dead long time ago… I would guess that the one 3.5v cell was with those 3 dead cells in parallel so it was drained fasted…
Anyways if you have a single cell charger, charge that one up to the voltage of the remaining cells, get 3 new cells of the same model ideally, get them to the same voltage as the others, then put them all back to the enclosure and move on.
Hey thanks for rhe reply. Well yeah probably its that. Its just weird bc I bought the cells one year ago only. So doesnt really make sense to me that they are already dead…
I had the hardest time getting my 3d printed NESE pack to balance properly. The BMS was constantly balancing the cells, and it felt like I was always chasing balance issues.
After switching to a standard welded battery pack, I was honestly surprised by how little the BMS actually needs to kick on. The pack just stays balanced much more naturally.
Any battery that relies on pressure between the cell and conductor is going to give you problems in a use case that isn’t completely stationary.
From what i’ve seen on these forums, the issues arise when vibrations cause the contact between cell and conductor to arc. Over time this arcing damages both cell and conductor in turn exacerbating the problem.
Use the search in this forum for the terms “NESE arc” and you’ll likely find some examples.
but the general consensus is that this type of construction is not suited for esk8 at all. Instead of burning your money and potentially your board by trying to repair this battery, you’d be better off looking into how you’re gonna get a proper pack built.
Are those cells all connected like batteries in a TV remote? Hmm, I can see that being a problem.
I’ve had enough trouble with power switches actuating themselves due to vibration (before they get half gummed up after a few thousand kms of road grime), to even consider the idea of TV remote style battery packs.
I squish my packs into a bed of silicone in the enclosure to prevent vibration / movement / spot weld fatigue, as well as give the compartment more compression strength - this has been an excellent decision.
Any cell that’s reached 0V is toast, or anything less than 1V really. I’ve got Panasonic cells that slowly discharged to 1.3V and have performed fine since, but I charged them and discarded a couple that dropped below 4.05v after a month on the shelf. Elevated self discharge is a clue that a working cell could become more of a fire risk.
