What voltage range does everyone’s (standard li-ion) packs roughly balance down to?
1) 4.10V - 4.15V
2) 4.15V - 4.20V
3) Over 4.20V
I’m trying to get a better idea where the existing BMS’ leave a pack after balancing. Thanks!
The poll feature isn’t working for me
Ive got three batteries that get frequent use and they all balance around 4.12 ~ 4.13
12s8p p42a diy and 200ish cycles
10s6p p42a diy and 600ish cycles.
10s4p Samsung inr? 10a cells ?cycles
Fucking incredible balance, modern lithium ions are so cool.
Based on the packs I build, using ANT, DALY and JBD BMSs, they all charge to about
4.15 New
4.12-4.15 after 100-500 cycles
Factory balance on the cells (After leaving packs idle for 2-3 days) is 0.02, after 100-500 cycles 0.02-0.035 or so. My own packs are all BAK CG50, LG M50LT and Molicel P42A and those tend to stick closer to 0.02 after time, but I also deal with a lot of chinese made scooter and ebike packs which almost always use LG MJ1, DLG 2600 or BAK 2500 cells and those drift more toward the 0.035-0.04 mark. They will still take 4.1v after balance tho
How do single-piece PCB packs hold up over time? Are they any more susceptible to vibrations compared to a flat pack?
This is all I found regarding PCB pack’s durability over time.
Wondering if a cell holder design could be combined with the PCB pack to reduce nickel stresses? Something like the snap together frames maybe?
My cells typically balance between 4.15-4.20. Both of my current boards have adound 20 cycles on them so the packs are babies.
I like to tape my groups together into a brick for each cell of the enclosure, if they will be touching neg2pos and it is a connection i am making with a series connection i will sometimes put a hard spacer just to make them sit together better mechanically but not necessarily to isolate them. I would put a bit of fish paper between and on the non series parts for extra cheap insurance against shorting if you have space or shrink it.
I put some ccf between these series parts for ascetics more than anything, then I shrunk the section, then cut open the shrink where I need to make the solder joints, then siliconed the joints:
I put some 1/8 adhesive neoprene under the package then 4 dime sized spots of silicone to hold it down after i was happy with it. Then i siliconed the edges in a way to not get under it so i can cut it out if i need to do repairs though it will be difficult
It’s unlikely to cause a shoulder short, but I’d advise putting a thin sheet of plastic in between anyways
super helpful, thanks!
Please help my tired head.
Connecting BMS in bypass mode.
Battery negative to one of two B- terminals on BMS.
Now I should be fine connecting the second B- terminal to the xt-60 going to load right? I want to avoid making some sketchy Y-connection. It’s better to just put both load and battery to B- right?
Should be simple but it’s 01:22… I will take a nap and re-evaluate tomorrow… lol
So technically yes, however the B- lead on a bypassed BMS only needs to be as big as the charge wire connected to C-, so like 20awg
Common good has the right drawing, the wafer thin layer connecting the 2 B- solder pads is only meant for like 20A or so
I have the 60 A version so I would have assumed the solder pads on the BMS would handle at least that…?
But maybe it’s easier doing just the thin wire.
You’re supposed to use 2 wires to get the 60A so not necessarily, I’d just get some 18 awg and fork it
I got a leaky cell…
welding these have been a nightmare, started off at 48j which was punching some holes thru the nickel. then did some test welds on individual cells and 41J was good; didn’t go any lower.
these are new LG m50lt cells i salvaged from an already-made pack, had to pull the nickel off and sand them down which i was very careful and gentle not to remove a lot of the cell’s material.
Im using 0.2mm nickel. why is the kweld just eating thru the nickel, its acting like im not using 0.2mm thick nickel. obviously, 41J is still too much as I punctured a cell. I guess this is the electrolyte?
I panicked and have the 3 welded packs in my garage in steel containers.
P42a does around 50J with no issues.
Appreciate any help on this a little nervous to do the rest of the pack, i guess I have to find how low I can go on the kweld while still passing the tear/rip test?
48J hole
Black hole is puncture spot
Update - 25-30j is what worked, never used this low of a power setting before, super weird. The p42a take 50j easy.
Maybe the cell became too thin when you disassembled it from the old pack and ground down the old spot welds. The positive contact in M50LT is very thin from the factory already.
I’ve had cells puncture when removing nickel but never when welding much less having the electrolyte spill out.
I would seal over the hole with some sort of non-reactive adhesive. I would then (gently) remove as much of the battery necessary to get off that one cell.
I’m thinking the other batteries/cells should be fine as long as you go and re-weld at whatever you determined worked. Make sure there is an ample amount of padding at the anodes and don’t run the pack very hard as there is less material at the anode to maintain a safe current.
Anybody feel free to correct me if I’m wrong
