Alright as it relates to series connections.
The conductor’s current ratings are extremely important when choosing how you will build the battery. Copying the battery before it is a terrible idea. TERRIBLE Not only have you changed the cells, but if you want to do this safely it requires more than just owning the tool. It requires enough research to understand what the amp capabilities of the cells are, their configuration and why its that way, the current capacity of the connections and the wiring of the pack. Proper insulation, isolation and reinforcement and securing of components is super important.
I’ll be helpful, but seriously. Do some more research if you’re evaluating the current carrying capacity of the nickel you used after the pack was considered finished. Before you install this in the board, get to work on reading and take suggestions seriously.
I know very little about the black caps on the batteries. However, I would highly recommend adding fiberglass reinforced tape to the back to strengthen it more. Hot glue might be little help depending on the quality of what you used and how hot things get in the enclosure during the summer. That can put a lot of stress on the pack if there’s any flex in the deck – and there’s always a little
nickel strip… 0.15x8mm nickel strip is not suffieicent for carrying the 60 amps that pack is capable of. Actually, that pack is capable of 80 amps and many have pushed the 30Q cells to that without issues - myself included. Currently, with a single 0.15x8 across the P groups and 0.15x8 x2 series connections, your pack has an okay rating of 34 amps and a hot rating of 44.
You do not have to remove whats there. But multiple layers is a nightmare and you don’t want to be just barely covering the amp capacity. Where did you buy the 0.15x8mm from and did you salt water test it even?
Go to liionwarehouse and order some 0.2x10mm nickel strip. DO NOT go looking for 12mm strip for 18650 cells like the 30Q. The inside diameter of the negative terminal is 12.8 mm. Buy 8 or 10mm width strip of 0.2. Also, 0.25 and 0.3 are available but a litter harder to find in the states.
For a pack with a max rating of 80 amps, I would suggest 0.2x10mm nickel. 0.2x10 has a good amp rating of 28 and a hot of 37.5. I just built a 20700b 5p pack capable of the same amps with this nickel. I use the same nickel for my P groups connections too. For the series connections, I would recommend a first layer of 0.2 that covers all 8 cells. The second layer should cover 3 positive and 3 negative terminals, the third layer should cover 2 positive and 2 negative terminals. With 3 layers, you have a good rating of 84 amps and a hot rating of 112.5 amps. Always stagger the connections in a pyramid shape to help distribute the amp load.
Heres the 20700b pack i just finished. 5P for about 80 amps. Thats 0.2 x10 nickel all around
Now, my first series layer of three goes across all 5 negative cells and covers all 5 positive cells, the second covers 3/3 and the third two cells on each side. Underneath all of them, there is a layer that connects the P groups together as well. If I had skipped the P group layer and just made my first long strip a series connection, lets look at where we have a problem. The first two negative cells in the bottom left corner can output around 15-17 amps each. If there was only one layer of nickel there, the current traveling from the first two cells to the third negative cell in the pic would be 30-36 amps, exceeding the good and meeting the hot rating of 0.2x10. Dont skimp on nickel. The same concept shown here can happen where you make series connections at folds, attach wires and main leads. Always think about spreading out the load and looking for weak points
Whats the plan for the series connection between the two packs? If its spot welded, it needs to be 3 connections min. If its under 3 inches you’ll be fine with 14awg x2 as well. Insulate it well. If using wires and you don’t have a great iron, solder the wires to the nickel and then spot weld them on to the cells. regardless, have more than just the 0.15 strip where the series connection joins the cell
For the BMS, do some research here and see the examples of well laid out and routed balance leads. Keeping them out of harms way, from crossing each other unnecessarily and from being crushed and shorting is very important. As is the proper wiring. When connecting balance leads, connect them to the negative cell of the series connection is good practice. B0 is battery negative. B1 is the first P group from there. So would be connected to the positive side of the cell that the batt main negative comes from. But since you heard what I said above, were gonna place it on the adjacent negative cell which is connected to that positive via the series connection. Same goes for the remaining leads. The side of the battery is negative, the whole can is. So if a balance lead shorts on the corner of the cell it connects to, that could be bad. Attaching it to the negative cell on the series provides some protection from short there
For the positive and negative wire, 12 awg will do. Keep it under 6 inches and use an XT60H connector or Xt90.