building

Maybe some cells have been sitting idle for a couple of months so before putting them into packs I topbalance all cells. I fully charge all cells, some cells will hit 4.20V, others 4.15V, don't worry about that. This step is done a few days before assembling the pack.

If you followed my design rules, all packs have the same capacity. It's a good idea to make a spreadsheet with the data of all cells from 1 pack. Later it can be used to measure degradation, in worst case to replace a faulty pack.

This popular method is easy to make nice busbars. I start with 10mm/ x awg wire which contains 7 strands of 1.5mm pure copper.
A busbar needs 3 strands, and they're already pre-twisted. A drilling machine gives the final touch.

Some builders use a mold to make the busbars. I tried it, but was never happy with the result. The corners are never a nice clean 90°, so I prefer working this way.

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My busbar runs parallel with the last cells, on the other side, keep 0.5cm/1/4 inch clearance.

Use the smallest set of 10mm to crimp these lugs.

May the force be with you....but don't worry the force is generated by this hydraulic crimper.

Commercial or DIY connector. For my first shelf I made the connectos myself, the second shelf has commercial connectors. Buy yourself some time and get the commercial ones. I put some solder in the connectors too, preferably with a larger size iron (75w).

Put the cells in the 4*5 holders. For larger packs I spread the cells with the highest capacity all over the pack.

Last time to check the cells before they go into a pack. Removing a faulty cell is a pain in the a**, so don't let a ten cent sleeve ruin your setup. More info about re-sleeving here

Try to get the positive side as clean and flat as possible, this will make welding the fuse easier and more "first time right" succesful.

The negative side can still hold nickel. The casing is not so strong, by removing the nickel you risk to damage the cell and lithium can start leaking. So I insist to leave the nickel on the cell.

Cut the right size with a decent wire cutter to cut the 0.15 nickel. One side has some overlap, don't remove it, it will be usefull later in the process

Welding process will start soon, time to get your saftey glasses. Trust me, during welding you can get sparks, it's not worth loosing an eye. Wear some work trousers and a lazy shirt.

Select the correct setting on your sunko. I use 12-6 for the nickel strip.

Don't start from one side and work your way to the other side. Start at the left and your next one should be on the right. Then in de middle. As you can see I have 2 welds/cell.

Put the busbar on the pack and push it against the nickel flaps. The 2 outer flaps can be removed or welded to the nickelstrip.

I cut 2.5cm/1inch long 4mm wide nickel strips to make sure the busbar has good contact with the nickel strip. 2 welds on each side will do the trick.

I add some solder to the small nickel bridges and to the nickel flaps at the left. On my 80p packs, I installed a nickel bridge every 3 cells.

Take a short break and dive in your childrens LEGO box. I made this setup to have a stable pack and to avoid stress on the negative side.

Another safety precaution. It prevents following occurrences: the fuse to touch the outer ring, solder flowing into the cell, melting cell holder & sleeve when soldering. Capton tape is used is 20mm, 18mm is fine too.

Another job for a rainy day. Cut off excess lead from the glass fuse.
For a 14s 80p, 1120 fuses will go through your hands & pliers.

Put the busbar in place. It can and it will move around while welding, that's OK.

It's easier then it looks. Put the welding pen with both feet on the 5mm thread of the fuse. Press firmly and when you're good to go, press the foot switch.

Once you welded the fuse, you need to bend the strand of the fuse so it touches the busbar. Keep the fuse in place with your thumb and use the index finger of your other hand to bend the strand of the fuse. Thanks to the capton tape, you can never make short.

First row is done. As you can see you have to be inventive to weld the last cell. I found this way to be the easiest and most reliable way.

Another row, same way of working. Make sure the leads of the fuses of opposite cells crosses each other at the same distance.

Solder the fuses to the busbar. I keep the leads close to the busbar with what's close to hand. My pliers or a screwdriver.

Soldering looks fine, to finish the 2 top row you only need to remove the excess leads of the fuse

....other rows. Let's weld & solder row 3 & 4. Excess of leads in row1 & 2 removed.

You made your first pack! It wasn't that hard wasn't it? You now have the knowledge to finish the other packs. Maybe you come up with a great idea, feel free....I even encourage you to share it.

One down X to go....for the next pack make sure the busbar of the negative side is pointed the same direction of positive busbar of the first pack!