How to assemble your 18650 cells into a bigger pack
When doing your power wall its important to get all into packs or strings depending on how you refer to it.
Im going to use 14s80p. That is 14 packs of each 80 cells inside. That will form up a 14*3.7V battery bank.
Today I’m going to tackle how i get this all together.
What i used:
- 5 Amp fuse wire (on eBay) or from here
- Big soldering iron
- 2.5mm2 copper cable
- 35m ring terminals
- 18650 holders
- Solder with flux/rosin
- Misc tools
- A lot of time
So how do i do this?
First of all i assemble the cells into an 80 cell pack with help of the 18650 holders. You need to make sure that the batteries is cleaned up in the ends going into those plastic holders or else you might end up breaking them.
When that’s done i bring up the big soldering iron. I recommend 100w or more. If you are using a smaller one you might end up heating them a bit to much and this will cause the cells to in worst case becoming a big “boom” 🙂
If the cells are a bit dirty clean the ends up just quickly before you start. I always go over the pack first and add some solder on each end. This will save me some time later on.
For creating the bus bar i just use normal household 2.5mm2 copper wire. The type that is solid.
I strip those cables down and then i use my drilling machine to twitch them all together into 3*2.5mm strings.
I bend this around the path that i have marked out on a wooden plate.
Then i just head over and crimp the 35mm lug into place.
To be sure that this will not come loose i like to add some extra solder as well just to be sure! When its done i just add some heat shrinks to the ends most for the looks of it.
I attach those bus bars to the packs of cells with some hot glue before i can start tagging down the fuse wire and the other wire.
You can do this 2 ways. You either work along all cells in one stroke and then cut of the excess material afterwards or you cut every strip down. Im not sure what method i like the most but the later is the one that may save you some bucks. The fuse wire you are going to use you need think twice about. First of all when you look into building these packs there is several types of cells. Im using laptop cells and those do in general not give out that much current on a short and you need to beware of this.
Many of those cells have their top around 10A. So don’t use wire that does not work with your application.
Im going to put through roughly 80A at most per pack and that’s 1A per cell. I have tested all my cells at 1A as well. Im using fuse-wire that is rated 5 times as high. And the best way you can see if this will work is like i did on the film -> Try the fuse wire and make sure it does blow directly on some of the 18650 cells you have. If the wire does not melt of directly you should not use this at all!
When thats done i just walk over and solder all those wires to the bus bar as well.
For the second side its important that you start with measure so that all those joints on the other side is attached. Then i go ahead and solder this side as well.
When done this is how it could look like
Disclaimer: Making packs like i do may be dangerous. You may burn your hand or even the house… I do not hold any responsibility against to what you do 🙂