2.4kwh diy powerwall from recycled 18650 lithium-ion laptop batteries - 18650 lithium ion cells

My 2.
4kWh Powerwall is finally finished!
I 've piled up a bunch of 18650 laptop batteries in the last few months and I 've tested them at my DIY 18650 Test Station --
So I decided to do something with them.
I 've been following some DIY powerwall communities for a while, so I decided to make one.
This is what I think of little Powerwall.
You can also see this project on my website: designed some 8 unit brackets to easily swap small units.
It takes a long time to print the stand and thankfully I have a friend to help print.
I had to print out nearly 100 brackets with a whole roll of fine silk.
Then there is the main work of more than 1500 welding connections in this building (Took a while).
I did most of the welding outside because the ventilation was better and the weather was fine, so why not use it?
The positive end of each battery is welded to the 4A fuse.
I chose 4A as this power wall was also to be able to run an electric car and I worked with EVPioneers for the Waterloo Electric Car Challenge.
And need to be able to provide burst current of 50a.
I only have enough 2A and 4A fuses and 2A won't give me enough power.
To be used as a power wall, I recommend using a 1 or 2A fuse as it will keep the battery within a reasonable range of work.
Yes, most of the new cells can do 4A (2C)
Continuous, but after a long service life in a laptop, it is safer to keep them below 1C.
The negative end is connected to the bus bar with the extra leg of the fuse cut off from the positive end.
This brings me to the bus bar.
I originally planned to use copper-either a flat copper tube, but after checking the price and feasibility, I decided not to use copper.
Without welding, I couldn't find an easy way to connect 8 battery modules to copper tubes and compare the price of copper and aluminum bars, I went and bought 1/8*3/4 aluminum bars.
Connecting 8 unit modules to the bar is another adventure.
On each of the 8 unit modules, the fuse is welded to the wire with screw terminals at the end, so as to be able to replace the 8 unit modules without welding.
To do this, I originally planned to use the 16gw wire, but after checking the 12gw wire I lay down, the 12gw is easier to peel off and will heat less under heavy loads.
On the positive side, I made the wires a little longer than the modules so that they could be placed in as little space as possible, and there was plenty of room to press the screw terminals to the top.
The negative end has a line bent to the same level as the positive line.
I covered this longer wire with as much heat shrinkage as possible, with 3 different sizes to prevent it from short-circuiting, where the positive end just sticks out to the end opposite of its screw terminal.
Now, in order to actually get the parts-I later spent $70 to go to the hardware store and bought 8ft aluminum, 100 12gw screw terminals, 200 6-
Nuts and Bolts (
They are the cheapest)
And some wood for the frame.
I cut the aluminum to a length of 1ft and then drilled a lot of holes in it for mounting the aluminum to the frame of the power wall and for connecting the screw terminals.
I don't want to take out a pair of pliers to fix the nut, and risk short circuit when screwing the package to the bus bar, I recently saw Adam Welch make some captive nuts in his solar shed bus bar.
So I designed a similar system with two nuts.
After printing out 56, I started to put the nuts in and slide them onto the aluminum bus.
The frame of this power wall is made of wood.
I should really use some
Install everything to a flammable location, but I can't find a metal cabinet of the right size or something like that.
I don't want to spend $150 on the fence either, so it's wood.
I have done all the tests on these cells and have done a separate fusion of each cell, and I don't think there will be any problems.
I will constantly monitor this looking for heater and check the voltage.
Each parallel group is separated by a piece of 1 × 3, and I install the aluminum bus bar on it.
Once all 8 busbars have been installed, I start adding the package to balance the capacity as much as possible.
I used the impact drive to tighten all the screws-I used to replace the aging NiCad in the impact Drive with 18650 s and it still works fine.
I did run into a 3D print stand that I stripped off, but thankfully it was at the end of a bus bar so it was easy to replace.
Finally, I added a 1/4 a circuit breaker to the front end and added a "clear acrylic sheet to the top of the battery to prevent any short circuit.
The inverter I am using for this is a 1000 W improved sine wave inverter.
This is the cheapest one on Amazon, and if I do this again, it may be an integral part of what I will change.
On the other hand, almost all of my workshops are powered by DC power supply, so the problem is not big.
I do like it though, as it heats my 60 w AC soldering iron better than a home air conditioner.
My normal soldering iron-Hakko T12 clone-is powered with DC and my lights and I will eventually add my 3D printer to that list as well.
I haven't put pressure on this battery yet and haven't done proper capacity testing, but so far this is awesome.