sparks all over the place

I want to sharemy very first experiences of building a battery for my diy ebike project. and maybe get a little help :blush:
This is how it looks from the outside.







And this is the battery itself.




And it works, yey But and there are a big question marks.

1. The spot welding was not so consistent with this shitty Sunkko unit. It sticks not so bad, but this could be much better with a professional unit. I don't have the confidence that all welding points are good quality.

2. My original placement of the BMS didnt worked as it supposed to. It would not fit into the case anymore, and i had a hard time designing and printing the case. My printer is too small.
I think it is too risky to place it like this, what do you think?

3. the thoughts what could go wrong came with the build and the most concerning thing is that it will get shorted somehow due to mechanical stress. Especially with the BMS mounted on the side.
I will tried to insulate everything as good as i can, especially this is i think the biggest difference to a Powerwall and this forum wouldbe for Powerwalls, i know but this will come later. Maybe there is someone who knows a thing or two about insulating a battery pack. There is not much to find out here.

4. sparks..
I got one small spark and a really major one :angel:
The small one was when iplaced the nickel strip and i forgot to tape a cell group and falselytouched it.
The big bang happenedwhen soldering the XT90 plug. I forgot to place the protection cap of the plug and i had to desolder it, then as dumbi am i touched with my soldering iron plus and minusand the battery demonstrated its power. After a few minutes of shaking and calming down i completed my work with a new soldering iron.





5. i cannot do it as safe as em3ev
when you have a look at those batteries it becomes clear that it is not a good idea to build a hailong 52V ebike batterie by yourself. I already ordered one.

What do you think, can i leave it like this? As i took the battery apart and writing this i dont think i can, i have to redo the case and do a better insulating of everything. Tips are welcome. Also i forgot to order the bluetooth module for this smart bms and now i can check voltages only with the multimeter.

After discharge / charge / half discharge the cells have to following readings:

1: 3.87V
2: 3.86V
3: 3.88V
4: 3.86V
5: 3.85V
6: 3.85V
7: 3.88V
8: 3.85V
9: 3.89V
10: 3.86V
11: 3.85V
12: 3.85V
13: 3.88V
14: 3.84V

feel free to comment...

Replace the XT90. It's safety/integrity has been compromised. Plus the solder connections aren't that great

Ouch! But not too much harm done! Nerves don't like it though right?

Cells will be OK, voltages are OK.

I'd suggest the connector is OK to resolder as is - marks are just in the solder.

Maybe solder the ends on the connector before soldering wires to the battery? Use heatshrink tubing over each wire.

Re insulation look at using kapton sheet or tape - it's a translucent brown, high temp & tough plastic film. Plenty on eBay & Ali Express, etc

Redpacket said:

Ouch! But not too much harm done! Nerves don't like it though right?

Cells will be OK, voltages are OK.

I'd suggest the connector is OK to resolder as is - marks are just in the solder.

Maybe solder the ends on the connector before soldering wires to the battery? Use heatshrink tubing over each wire.

Re insulation look at using kapton sheet or tape - it's a translucent brown, high temp & tough plastic film. Plenty on eBay & Ali Express, etc

Click to expand...

+1 to everything said.
Additionally, carefully presolder the wireends, after carefully smothing them into their drill. Then snip of the end, thant you get a nice tight "cylinder" of already soldere wire.
XT60 are a beast to solder, i can confirm this. Cowards have the chance of just installing a Car fuse 30 Amp into one battery wire, when you pull it you can solder the XT free of power.