Building my 14S6P VTC6 Pack - Your opinion

Hello,

I'm building my 14S6P pack with VT6A that I plan to use on my upgraded Coast Cycle Buzzraw with BBSHD and ASI855.

I'm using 0.15 pure nickel strip 10mm at 8ms pulse. The weld is very solid. I went to 12ms on the serial connections.

I consider Side 1 finished and I'm almost done with completing the serial connections by adding some additional strips (on side 2)

Then I'll wire the BMS (Neptune 15) and discharge wires and finish the pack with some kapton. I also plan to add desoldering bread on the positive and negative areas.

Any opinions on the pack so far?

Side 1


Side 2



Thanks !

this looks right if you do 6 serial connections



the other side (side 1) of the pack looks like your missing 2 serial connections on the p-group ends and middle serial connections but????

okp said:

Any opinions on the pack so far?

Click to expand...

The good news is that it looks like a neat job, and you can be proud of that. And those cells are some of the best high power 18650s available. Lucky you.

Unfortunately, as mentioned above, there isn't a connection for every series cell (appears to be 5 instead of 6 for each set of 6P). This means 2 things:
1. The current capacity is reduced.
2. The current sharing between cells is not balanced, since some cells are only connected to the nearest parallel cell.

This will be an issue if you expect to use those (very capable) cells like they could be used (up to 30A each). Some cells will not contribute as much, and some moreso, creating imbalances and reduced life.

Also, 0.15mm is relatively thin to use with these high power cells, so even if there was a series connection for each cell, you'll be severely limited in current anyway, maybe 7A continuous per cell, or 42A for the pack. https://www.endless-sphere.com/forums/viewtopic.php?t=98849#p1447486

You didn't mention what current you plan on pulling from this pack, so maybe it isn't such an issue as it currently is if you're only planning on pulling 35A continuous and maybe 60A peak.

If you want more than that, then I would consider removing (gently grinding with a Dremel) those series connections, and running new ones, maybe double up 0.20mm nickel.

thanks a lot serious_sam and goatman for the feedback

I've reinforced the pack with additional layers of pure nickel 0.15mm and increased the welding pulse to ensure good fit. The welding was so good that I went for this option instead of replacing the existing strips (which would have been a pain).

What I understand is that the cells are over rated for the way I've welded them, as the limit of the pack will be cause by the points you've mention serious_sam.

My plan is to use it with a BBSHD on 52v and ASI controller on a 10 speed bike so I'll be maximum 60A... but that's just guessing. I would need to check what my bike is consuming today on 48V and build from that.

I also plan to solder desoldering braid (pure copper) at the positive and negative areas of the pack cause so far, here is only one 0.15mm layer.

If I'm courageous enough (which I'm gonna do) I will double ALL existing connections with desoldering bread as well, and that will probably make the deal for higher amps.



Here are some new photos of the pack in progress.

Side 1



Side 2 - you see here on the left/right the positive/negative that I will beef up with desoldering braid. I'm still missing in the middle some horizontal serial liaisons that I will do tomorrow (I was missing nickel strip)

FYI, I bought this10mm 0.15mm nickel strip which seems to be rated for 35A; but I shaved 2mm to ensure perfect clearance

https://www.ebay.fr/itm/263057825976?euid=null&bu=43093507404&crd=20201009072819&osub=-1~1&ch=osgood&cp=1&sojTags=bu=bu,ch=ch,segname=segname,crd=crd,url=loc,osub=osub

Hey folks, thanks for the kind advices !

I've reinforced my parallel and serial links as well as the positive and negative of the pack.

Then wired the Neptune 15 BMS (which is very cool !)

Voilà !