Next steps! I’m at school and found a few Saturdays to procrastinate. Many thanks to my roommate Roger who let me take up the kitchen table for almost a month of school insanity while I tried to work on it between classes and in my freetime.
Anyways, the next steps after labeling all the cells was to do the painstaking process of manually balancing all of the cells and bringing them to a universal charge.
First, I worked on each P group, bringing them to even charges if they were not already at them. I used a 1s charger board that plugs into a USB cable (TP50xx or something I don’t remember, I bought them a long time ago). It’s pretty safe because it only charges at 500ma. This process took quite some time, requiring the charging of each individual 24 cells when necessary.
Once all the P groups were brought to the same charge, I paired them all up into their 3P groups and set them aside until I was able to solder them.
I didn’t really take many pictures as I was soldering the cells together because it’s pretty routine stuff. I will explain the way I did it breifly - stack the cells together using their adhesive to hold them, then fiber tape the non-terminal end. Check the length needed to span across all three cells and strip a piece of wire to that length, tin it with a good amount of flux and solder. After that, I cut off the piece while it was still hot.
I then fluxed all of the terminals that I was going to solder together, and laid the tinned wire across them. I had the 3P pack stuch in a vise with a towel so as to not puncture the batteries. This process was really annoying, holding the wire in place and adding solder to it while simultaneously trying to not heat up the pouches too much.
Here’s a picture with most of the parallel packs finished off.
For some reason wiring up balance leads has always been confusing to me, so I chose to do it as I went this time. I slowly soldered together the S groups by joining the P groups along the line with small bits of insulated silicon wire. I added the balance leads right onto there, and later realized after that I didn’r quite have them right, so I ended up switching out the leads within the connector because Ihad already taped it up.
I consider myself to have pretty good soldering skills and I am confident that all of my joints will hold up to the test of road vibrations. As I went along, I taped each balance lead section to the batteries, trying to make sure all the leads didn’t overlap.
In order to wire the BMS to the parallel packs, I made sure that all of the opposing batteries were at the same charge, and then paired balance leads from the ends of the pack, counting down into the center. At this point I made sure to check the charge one the big balance connector, and I found some discrepancies - this is why you always use a multimeter to check before you plug it in and fry your BMS.
After fixing the discrepancy in charge, I did a final check on the balance of all the cells and plugged it into the BMS. Nothing fried so I was happy. Next I had to wire in the rest of the important cables, charge port, pos and negative, the BMS, etc.
I will insert my schematic here later, it’s on my desktop at school.
I made sure everything was well taped up and started adding some foam bits before soldering to the BMS and Pos, Neg.
I skipped a lot of steps here between pictures, but here’s a picture of the BMS with all the leads soldered. Between the last pic and now, I designed a new enclosure with an extension in the center to hold the BMS and wires without crushing them, and support the sides of the cells. I put in the charge port and soldered it into the mix as well.
I quite like this connector for a charge port, but I need to design a small plug to stick in it while riding, because there is quite a lot of open space when the connector isn’t plugged in.
At this point I had to get more screws and then wait for the last piece of the enclosure to print.
Here’s a shot of the finished product - so many hours were put into this. Unfortunately, the troubles weren’t quite over. Somehow I had managed to break my GT2b when I was soldering it, so I picked up a Vx1, and I quite like it for this board.
