18650 stacking cells in 20s15p (2 layers of 10s)

[smeagol222]

Hi

I've tried to find if this is okay to stack 18650 cells when build a pack.

I'm building a 20s15p pack, because of size constraints I cannot just have one layer, I need to stack them

There will be 2 layers of 10s connected by longer nickel strips. My idea is to put a piece of plastic card between the layers as insulation. And them some thing foam also.

Since the nickel strips would be longer to curl around and connect the two 10s in series to make 20s, I was thinking to double up on the nickel strips thickness

Or would it be better just to connect these with some 6 gauge wire? Maybe 4 short pieces spaced evenly apart?

See image

 

[j bjork]

I have thougt about the same thing too.
In my case it will be a very tight fit, there will be no room for wires on the sides.
If I do it this way, I will make it like 2 packs that can be disconnected in to 2x10s to make it possible to charge with an icharger 4010 duo.
My plan is to have a bit longer nickel strips on each cell in the first and last group (the positive and negative). So I can solder one big or several wires and to them, and run them over or under the pack.
I would do the same for every balance wire too, but on them I would just have a bit longer nickel strip on the parallel on the negative sided cells. (no risk of short cirket aganst the side of the cells).

 

[smeagol222]

hmmm you make a very good point- as I wasn't going to add a BMS to this pack.

I also have an iCharger 1010B+ which lets me balance 10 cells, super easy if I have two 36v 10s packs, only downside I just have to do them one at a time, or do a parallel board.

Since its 15p I'm sure it should be okay to do this at the full 10amps (iCharger can do 300watts) this works out to only 0.66amps per cell which I think is fine.

I'll be using 6 gauge tinned copper flex wire with some PRC 8 connectors as output and connection between the packs

 

[fechter]

You can see a pack where I stacked two layers like you are thinking about:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=79324&hilit=ammo

I built the pack flat to start with and folded it in the middle. You need some very strong insulation material between the layers. I used polycarbonate sheet. I also bound the halves together tightly after it was built to prevent movement between halves.

 

[MJSfoto1956]

This is how many of the AliExpress 72V battery packs for eMoped/eScooter/eMotorcycles are designed. They use 140mm long nickel serial tabs. This is to keep the POS and NEG outputs separated on the other side.