Dow-Kokam (NMC) vs. A123 (LiFePo4) comparative analysis...

Harold these is my concern is just the clamping of the tabs is enough ? How well do the tabs play together how wide does the contact area is need to be. I think we need a copper crush plate. That being a plate of copper with a line dippled 2mm wide across as a spread of persure ( point ) across the tap with crush being in copper ?
 
Polished copper that is pure is the best conductor we can get relatively inexpensively. It is about 4x better than brass. Alu alloy is good until it gets oxide coating and then the resistance goes way up. Agnuism is using brass. He believes that it will work due to the fact that the tabs are squashed together, and the brass is mainly a mechanical connector and heatsink. Brass is better to tap and hold thread.
otherDoc
 
If people don't mind a slightly taller or wider pack, the threaded-rod clamping idea would still work, and perhaps better than individual clamps, since it would probably evenly spread clamping force across all the cells' tabs, rather than possibly having some clamps with lesser or greater force than others and thus potentially different contact resistance.

Basically it'd use cmpletley insulating blocks that would clamp unmodified tabs together for series connections, and each block would stick up (or out from the sides of the cells) enough to allow a hole all the way thru all of them, with plenty of structure and insulation room between the hole and the cells/tabs. The threaded rod or whatever would be placed thru this series of holes from end to end, and used to clamp teh entire assembly together.

If a pack frame is desired, then instead of individual blocks only at the tabs, an entire frame cast or machined for each cell that acts as a tray as well as a press for the tabs.

I dont' know what materials would be best for either blocks or threaded rods, to help prevent thermal expansion/contraction over the range of useful temperatures for the pack, but there should be something that would work that would also not
"flow" or stretch under compression or with the forces of holding it together.
 
I think there needs to be some slack before the bus bar ( a Z in the tabs before the connetions ) for expanance as not to tear the tabs. Slack...
 
Anyone selling good bus bar to get these cells up and running? I am going to get cellman's BMS, but I need some good way to mount these cells in such a way to make them removable if they go bad.
 
I'm thinking of using a clamp made of copper and soften that can be beat down on the taps with a air gap at top so as to be cut later if need be for a 1p 16s ( or ) for a common bike of 60v20ah plus at 30amps or plus ?
 
Well Ideally I would like to make it removable so in case some cells show weak signs after a few cycles, I can remove and replace it. So no one have any good off the shelf ideas to build these things? Will I have to hack some solution?
 
This one by megacycle shows promise from the other thread. Amberwolf has a clamping idea that might work also. both are in the other thread.
otherDoc
http://endless-sphere.com/forums/viewtopic.php?f=14&t=36780
I wish there was a way to combine this thread with the linked one. Between the two there are some good ideas for a fairly simple A123 large cell connector.
 
cell joiner3.0.jpg

this is how i think i might join the cells, its a crappy paint drawing but i think its about right..
the black is a hard plastic that is the thickness of the cells
the big hole is for the cell to sit
the outside and center holes are for threaded rod
the two holes for the tabs are for threaded rod but possibly powder coated or coated somehow to be non conductive

first you get a 270x200x3mm piece of stainless with a hole cut out for the first tab to go through and thread all the rods through it,
then you place the cell in the plastic with one tab down and one tab up and thread it onto the rods pushing the first tab through the first piece of stainless
the next cell goes into its plastic holder with one tab up and the other tab down to connect the tabs together to make a series
you keep going till you have your pack then cap it off with another piece of stainless, tighten all the threaded rods

for balance/bms wires you could drill into the plastic to make a path for the wire and solder that onto the tabs, or a spade connectory type thing imbedded into the plastic that contacts by compression also
 
Mcmaster Carr has some fiberglas threaded rod but it is 3/8 inch diameter. They have nylon stuff threaded also but this would probably not be strong enough to put pressure on the tabs. I'm not clear on the stainless part because it sounds to me like the entire outer plate would be conducting. Is this correct darkone040
otherDoc?
 
So connecting the taps of aliunium and copper tabs for series. The aliunium will expand greater with heat and need no-oxy, does this only happen if over discharged ? Is there movement to be concern about at normal discharge rate ? Becauseof heat. If only current thru taps then a plastic buse bar would be o.k. to wrap the taps around ?
 
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