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I'm looking for information on where to buy the correct crimps, and how to correctly crimp, these types of ground straps, for inter-cell connections. My google-fu is not helping me much. I can find the right ground strap material, but not sure the right term for the crimps, or what crimping tool to buy. Can anyone help?
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The holes have 76mm centers, which is 3 inches, so I'm guessing they're about 4 inches long overall, and about 3/4 or 7/8 inches wide. A short length of 1/2" copper tubing can be easily hammered flat, and will be close to 3/4" wide. Cut to length and drill holes as you need them and you have a one piece connection strap.

Google: make battery connector from copper tubing
 

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Problem with rigid connections in a mobile use case

is all shock/vibrations between cells get transferred to the posts, very often not at all strong laterally, not designed to be structural.

Personally I'd stick to tinned fine stranded "boat cable" (UL1426 105c)

cut to length so no tension

and properly crimped.
 

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Grote has braided ground straps with crimped-on ring terminals - they apparently just gather up the braid into a bundle to use a common crimp terminal. They don't anything short enough, but their products illustrate one way that they could be built.

The logic in favour of a cable connection make sense, but at this length a heavy round cable would have almost no flexibility, which is presumably the reason for wanting a flat braided cable.
 

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Fine stranded boat cable is pretty flexible.

So long as there is a curve in the connection between posts, I do not understand why "more flexibility" would be desirable?
Absolutely. But these straps are only 76 mm on centre, so the cable length with typical terminals is only about half that, and in the gauge of cable used for this that's almost a rigid bar, even in boat cable. I agree that a curve would be good, but it's hard to get a curve in that short distance.

Some people have used solid copper straps for this sort of application, but crimped a curve into the middle to allow some flex. There are even commercially available bus bar expansion joints, which use a stack of thin sheets (in aluminum or copper) for flexibility, welded to solid end bars.
 
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