[dtbaker]

Has anyone come up with a slick jig or method to increase the 'bend' in the stock busbars just enough to shorten the bolt hole centers to match the distance between terminals when connecting end-to-end?

I would like to use a busbar to bridge from one stack of cells to the next, and need to 'adjust' some straps... can't believe that TS didn't place the terminal to give same distance stacking in either direction!

I hate to use the cells themselves to squeeze the bar into shape because I think it might put too much side load on the terminals. So... anyone have a slick (fast) way to do it?

 

[EVfun]

One possibility is to take a rat tail file to the holes and slot them a little bit. I had to do this with my braided straps to go end to end on my 60 amp hour TS cells.

 

[dtbaker]

One possibility is to take a rat tail file to the holes and slot them a little bit. I had to do this with my braided straps to go end to end on my 60 amp hour TS cells.

Huh, I would have thought there was enough play in the braided straps to make up the difference? Are those things stiffer than they look? Where did you get them by the way? Only source at a remotely reasonable price is in AU.


I could slot them... centers are only 3/16 shorter end-to-end than stacked for the 100ah cells, but I hate to lose that conductive area and flat bearing surface right under the nut.

I'd rather increase that bend in the straps a little to shorten the center to center, but it is hard to do accurately without a lot of trial and error unless somebody has happened on an easy jig or method.

 

[Woodsmith]

Post a photo of one of the bus bars, a before and after would be nice to see what you want to do.

Depending on the size of the existing bend I would be tempted to make up a little jig to fit in the vice jaws.

If you made up two removable jaw covers, like the soft jaws that you can get, weld on two vertical round bars on one jaw and a single vertical round bar on the other so that the single one falls between the other two when the jaws are closed.
Place teh bus bar in the vice and tighten. The round bars will then put a U shaped bend on the middle of the bus bar. The size of the bend will depend on the diameter of the round bars and how far apart the round bars are are on the one with two on.

Do you see what I mean?

 

[dtbaker]

Post a photo of one of the bus bars, a before and after would be nice to see what you want to do.

yes, this is what I was thinking, but i don't need very many, and so hate to invest too much time into making a really nice jig.

The 'standard' busbar from TS is several strips of CU with a slight bend pre-formed in the middle, and has shrinkwrap holding together the laminates. I was thinking about clamping the ends with C-clamps, and just squeezing the c-clamps in a vise; but it would be pretty hard to keep straight without constraining the clamps in a simple jig.

I COULD just increase the bend in the middle 'by eye'... making a taller hump would shorten the strap.... but will take several iterations and probably have to re-drill the bolt holes as the bend radius will affect the laminates hole alignment.

 

[JRP3]

I made up a custom "strap" out of copper bar stock that had a taller "hump" in it to pass through the hall effect pickup in my EV Display. I used a combination of vice grips, clamps, hammers, and a socket as a form, then drilled the holes after I had everything shaped the way I wanted it. Bigger pain in the ass than it seemed at first, especially getting the tabs for the holes to be really flat. After I finished it I thought it would have been easier to have just cut the shape out of wood and used the two pieces as a form, stick the bar in between and clamp it in a vice or press.

 

[Woodsmith]

yes, this is what I was thinking, but i don't need very many, and so hate to invest too much time into making a really nice jig.

The 'standard' busbar from TS is several strips of CU with a slight bend pre-formed in the middle, and has shrinkwrap holding together the laminates. I was thinking about clamping the ends with C-clamps, and just squeezing the c-clamps in a vise; but it would be pretty hard to keep straight without constraining the clamps in a simple jig.

I COULD just increase the bend in the middle 'by eye'... making a taller hump would shorten the strap.... but will take several iterations and probably have to re-drill the bolt holes as the bend radius will affect the laminates hole alignment.

If the tabs stay in the same alignment then the holes won't move regardless of the bends in the middle. Try bending a U in the middle of a phone directory. If you keep the spine flat on the table and the open edges also flat and lift the middle up to make a hump the pages will slide but the spine and the open edge stays true and square.

If in doubt stick nuts and bolts through the holes and tighten before bending.

For a really quick bit of bending in the vice I have stood a U bolt (exhaust pipe clamp bolt), points downward in the vice against the front jaw and then stood a long bolt, head downwards, against the middle of the back jaw. I then placed a strip of material between the upright bolt and the U bolt and tightened the vice.

Three short strips of 1" angle stood on end works as well but leaves sharp creases unless you round off the angle first. You may need to tape the angles to the jaws to stop them falling off.

 

[EVfun]

Huh, I would have thought there was enough play in the braided straps to make up the difference? Are those things stiffer than they look? Where did you get them by the way? Only source at a remotely reasonable price is in AU.

I could slot them... centers are only 3/16 shorter end-to-end than stacked for the 100ah cells, but I hate to lose that conductive area and flat bearing surface right under the nut.

I'd rather increase that bend in the straps a little to shorten the center to center, but it is hard to do accurately without a lot of trial and error unless somebody has happened on an easy jig or method.

I could have pushed into the braid, it would have puffed the braid a little. I would have had to pre-push them. They are quite flexible for about 10 degrees and/or about 1/10 inch up and down but it is still a 1/0 cable worth of copper in there. Shoving it shorter would take a bit more force. I did import them from Australia. I also ordered my battery regs and a fuel gauge driver from them. I've been quite happy with EVworks.

Slotting them wasn't hard, copper is soft. For the end to end terminals I also had to cut one end shorter with a hack saw because the solder pads for the BMS signal loop wiring would have been uncomfortably close to the straps (not an issue with the bigger cells.) I cut the positive end about 1/16 inch past the slot and slotted the negative side inward an extra 1/8 inch.

You may be able to gently clamp them inward just by making 4 blocks for the bolts. They would hold the ends flat and the holes true and you would be able to use a C clamp on the blocks to shorten the straps. Electrical grade (nearly pure) Copper is quite soft.

 

[major]

....would have been easier to have just cut the shape out of wood and used the two pieces as a form, stick the bar in between and clamp it in a vice or press.

Hey Dan,

I did basically what JR describes. Made a die set out of phenolic. Hardwood will work. I used it for solid copper and strips. Up to 1/8th inch thick and 3/4 inch wide. In a vise and also with a hand press. Bet I've done a hundred or more. I'll see if I can get some photos tomorrow.

For some bigger one-off humps in Flexibus, I just cut a notch in a 2x4 and used a wood dowel (broom handle) and hammer.

major

 

[major]

I'll see if I can get some photos tomorrow.

Photos attached.

 

[GerhardRP]

Has anyone come up with a slick jig or method to increase the 'bend' in the stock busbars just enough to shorten the bolt hole centers to match the distance between terminals when connecting end-to-end?

I would like to use a busbar to bridge from one stack of cells to the next, and need to 'adjust' some straps... can't believe that TS didn't place the terminal to give same distance stacking in either direction!

I hate to use the cells themselves to squeeze the bar into shape because I think it might put too much side load on the terminals. So... anyone have a slick (fast) way to do it?

Have you considered anealing them? Take them to red heat with a torch and natural cool. When they are dead soft, the strain should be minimal.
Gerhard

 

[GerhardRP]

Has anyone come up with a slick jig or method to increase the 'bend' in the stock busbars just enough to shorten the bolt hole centers to match the distance between terminals when connecting end-to-end?

I would like to use a busbar to bridge from one stack of cells to the next, and need to 'adjust' some straps... can't believe that TS didn't place the terminal to give same distance stacking in either direction!

I hate to use the cells themselves to squeeze the bar into shape because I think it might put too much side load on the terminals. So... anyone have a slick (fast) way to do it?

Second hack at this problem:
Buy a 3-foot piece of threaded rod the diameter of the holes. Cut it in half. On each end attach one of your bussbars with suitable fender washers. Put each end in turn in the vice and squash to the required separation.
Gerhard

 

[dtbaker]

...it would have been easier to have just cut the shape out of wood and used the two pieces as a form, stick the bar in between and clamp it in a vice or press.

very nice looking die there.... I am considering just a quickie wooden form, I only have to do a handful, so hate to invest too many hours in a die. what is the diameter of the hole/bump required to shorten up your straps, and how much did it shorten them?

my straps I only need to shorten by 3/16.... for 100ah TS, to match post distance endways versus normal orientation.