My A123 modules got a beating at a combat robotics contest recently. They held
up fine. They were charged with a BMS on each cell. Discharge rates overlapped
my truck. These cells saw far more G-forces than normal. But I needed some
testing on the structural side of the design to make sure nothing stupid
occurred. The spot welds were of particular interest. The owner uses A123’s in
his robot. Now he’s sending 100 more for more packs to be made. Sweet. This time
however he has a different module layout he wants to try.

I used nickel as the conductor since copper is apparently next to impossible to
weld with a CD welder. I was told this and didn’t believe it. Then I tried to
for 3 days. Nope. Even as fancy as my CD welder is. Nickel is universal for cell
assembly. But not only is copper cheaper, it also is a better high current
conductor. That’s also what makes it harder to weld. It basically has no
resistance. Since I’m making over 70kw now, I have to make sure a module can
pass 100kw for the future (fingers crossed). If copper ever gets used, I’ll have
to buy/make an inverter type welder.

I just won’t be satisfied until I can spin tires on dry pavement at will!

I needed a new transmitter pack for my old JR X347. I went to Fry’s and got a pack of 8 2750mah NIMh cells to replace the old 600mah nicad pack. I don’t fly anymore, but these packs are for testing Victor motor controllers that I rebuild for the Combat Robotics crowd. In a couple of weeks Combots will be at the San Mateo Fair Grounds again!!

Here are the first 2 cells getting spot welded together. I had no fixture so I used this block and some scotch tape. I cut up some .010″ nickel strips to spot weld the pack together. The settings on the welder worked fine for this thickness of nickel.

Fold them in half.

Push them together.

Now I’m spot welding pairs of cells together.

I added the next pairs of cells to spot weld.

Here is the finished JR X347 pack.

I took the old JR X347 cells found the dead one, added a good one to them and made this my Futaba AM transmitter pack. Note that the settings on the spot welder are lower. These nickel tabs are recycled from the old Futaba pack.

Here is the new cell being charged by itself to bring it up to the same 100% state of charge that the other cells are at.

I started a new blog about the repair of my, new to me, 1993 Cummins Dodge truck. It’s my first diesel.

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