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Originally Posted by Daox
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I haven't seen it yet but now it makes sense. The higher, electromotive potential of lithium protects the aluminum. . . . makes a lot of sense.
I'm still reading up on aluminum spot welding and it is not as easy as I first thought but not impossible either. My hypothesis is a rectangular, tungsten tip joining on the edges of two sheets will give the heat concentration needed to make a nugget joining the two. A capacitive discharge, short-length, welder should then spot weld the metals together. Testing will prove the approach.
One other interesting approach is to use a pair of sheet steel strips, "|<tabs>|", around the two tabs and spot weld the strips "|<tabs>|". The steel provides the resistance and heat to hold and form a proper weld puddle between the aluminum and copper. Certainly a clever approach but I have to admit I'm looking back at your mechanical clamp with more insight.
Driving home, the answer came, aluminum press rivets:
- Equalize cell charge
- Clean tabs
- Fold tab over end conductor
- Rivet and/or clamping machine screws (solder if practical)
- Align second tabs
- Fold tabs
- Drill first rivet hole
- Press counter-sunk rivet
- Run balance wire around rivet and out side
- Drill and seat rest of rivets.
- Stack next cell and repeat riveting.
Pressing the counter-sunk, aluminum rivets provides a permanent joint. The rivet shaft diameter determines how much current each can carry, not counting the current through the mated surfaces.
A 25-pin D connector can easily handle the 16, sense wires. For cell balancing, there is no need for more than 1 amp. There will still be spare pins to operate the isolation MOSFET.
Bob Wilson