WEEK 6: Finished 54 battery holders! Painted and all batteries repacked, assembling battery modules, wiring planning

This week I managed to get all the battery modules cut out. I had to buy another 1200 x 1200 9mm sheet of plywood which I only used half of. I managed to cut out 56 plywood holders (2 spare), which I then finished up with the belt sander to remove rough edges for painting.

I got a couple cans of black spray paint to make the modules look neater and be more weather proof. I had a lot of trouble with the spray cans not working so got nice and dirty after puncturing one of the cans that had clogged up lol trying to figure out why it no work :)

I then spent a sleepless night on Thursday sorting through every single cell and doing what is known as repacking, which capacity matches every parallel group of 18650's. In my case this meant each 'module' had to have the same total capacities. As all the cells are recycled in my build from old laptop batteries, this means they are all different ages and capacities which have to be matched up for the pack to perform well.

An online program known as www.repackr.com/ helps rearrange cells into equally sized capacity modules. It took me roughly 7 hours to get this done and I was glad by the time I finished!

I then inserted all the cells into the plywood module holders and assembled them so they are ready to wire together now!

This is the wiring plan for each module. I need to reduce the amount of copper used for each module so I don't go through like 30m of house wiring. The copper bus wires do have to be rather large though to carry up to 250A current at full capacity.

I then grabbed as many scrap resistors from our Mechatronics class which I will be using the resistor legs to fuse each cell when I spot weld them. These fuses will then be soldered to the main copper shunts making for a more efficient and safer wiring process. I went to a couple electrical stores seeing if they have any scrap copper wiring I could use for this but it is quite difficult to use as a very fine strand copper will become messy and hard to remove insulation and bundle together, and a solid core it much harder to solder to. I would like to use with the house wiring as it is a several stranded copper core which is easier to bend and wire in as well as solder. The only problem is removing all the insulation as there is quite a bit of time and waste from it. But it will all be worth it hopefully!