EVE-280 cells should these be clamped tight or spaced for expansion?

[ArthurEld]

Batteries are the future. I'm going wait until you guys prove out the spring concept then I'll copy yours. ?
I'm still not ready to torque my nuts to 33 inch pounds either.

 

[vtx1029]

Well that is not at all the same. I am curious how you would accurately measure 12 psi on one of these fixures?

You would need to use a load cell and convert that 12psi to lbs per sq inch.

 

[Colonel.lp]

Batteries are the future. I'm going wait until you guys prove out the spring concept then I'll copy yours. ?
I'm still not ready to torque my nuts to 33 inch pounds either.

Don't, because 33inlb is the value required for 1 m6 nut. What setup do you have?

 

[Colonel.lp]

There really isn't anything to prove. As long as you measure the original length of the spring and know the spring rate, it's a done deal. Just wind it down 1mm for every kgf you need.

 

[Colonel.lp]

Deleted. Nothing of interest here, just fat fingers and a touchscreen.

 

[Pyrofx]

I'm curious how much it costs for a torque wrench that can accurately measure 6 psi or 12 psi

They dont read psi. You get a torque wrench that reads in inch pounds.
Now if you were tounge in cheek ......

 

[HRTKD]

I wouldn't, I'd measure the torque required to provide 300kgf clamping force on the side of the cell. I.e. 33inlb over 6 x m6(1/4") nuts. So 5.5inlb on each of 6 nuts + drag for my nyloc nuts.

But really I wouldn't do that because it's fraught with errors. Springs are the future man! ?

Good luck finding a torque wrench that goes down to 5.5 in lb. My 1/4" Snap-On digital torque wrench starts at 21 in lb. I'm not saying they don't exist, just that they're hard to find and if you buy one, what the heck else would you ever use it on again?

 

[Colonel.lp]

Good luck finding a torque wrench that goes down to 5.5 in lb. My 1/4" Snap-On digital torque wrench starts at 21 in lb. I'm not saying they don't exist, just that they're hard to find and if you buy one, what the heck else would you ever use it on again?

Exactly. Power to the springs!

 

[ArthurEld]

Don't, because 33inlb is the value required for 1 m6 nut. What setup do you have?

Don't laugh. This is temporary

 

[sremick]

Good luck finding a torque wrench that goes down to 5.5 in lb. My 1/4" Snap-On digital torque wrench starts at 21 in lb. I'm not saying they don't exist, just that they're hard to find and if you buy one, what the heck else would you ever use it on again?

Can't be that hard to find, I just looked and I happen to have 2 in my possession already. One is fixed at 2 in/lbs, the other goes from 0.3-1.15 Nm which is 3.1-10.18 in/lbs.
My other one goes from 15-75 in/lbs.

 

[Luthj]

For low torque I like these beam units. Inexpensive and accurate enough.

 

[Colonel.lp]

Or just hang a weight off a spanner or socket at the correct point. ? Eg. 5inLb is 1lb at 5inches from the center of the nut, spanner must he completely level for it to work.

 

[ArthurEld]

Can't be that hard to find, I just looked and I happen to have 2 in my possession already. One is fixed at 2 in/lbs, the other goes from 0.3-1.15 Nm which is 3.1-10.18 in/lbs.
My other one goes from 15-75 in/lbs.

You need one more that has 12

 

[Colonel.lp]

Now this is what I was talking about with the uneven sides to the eve cells. You can see the marks on my end plate where they are touching. A thin line across the top and 4 thin patches vertically down the sides. I would say it's the same on all cells. Hmmmmm.


It's a shame @ghostwriter66 has already spoken to the engineers, I would have been interested what their take on this is in relation to compression.

 

[Luthj]

Might be worth using some 1/16-1/8" high density neoprene rubber? My cells were fairly flat (flatter than that) but the edges were still the primary contact points. However only 20 thousands of expansion would change that.

 

[Colonel.lp]

Might be worth using some 1/16-1/8" high density neoprene rubber? My cells were fairly flat (flatter than that) but the edges were still the primary contact points. However only 20 thousands of expansion would change that.

20 thou? Like 0.001mm? Can you even measure that without a serious set of feeler gauges? ?

I will look into the foam, or just short the terminals and get a tan until they have swelled enough to fill the gaps.

 

[vtx1029]

Here's my plan for the batteries in my trailer. Space was the reason to stack them.

 

[Airtime]

Good luck finding a torque wrench that goes down to 5.5 in lb. My 1/4" Snap-On digital torque wrench starts at 21 in lb. I'm not saying they don't exist, just that they're hard to find and if you buy one, what the heck else would you ever use it on again?

I bought this one for $45, I had needed one a few times already for other reasons so was time to buy one:
https://www.tekton.com/1-4-inch-drive-dual-direction-click-torque-wrench-trq21101

While 10 in-lb is the lowest major increment, with the vernier has 1 in-lb markings and you can go a bit lower than 10. Of course it will start to lose accuracy at say 6 in-lb but I don't think that matters much in this application.

 

[HRTKD]

I bought this one for $45, I had needed one a few times already for other reasons so was time to buy one:
https://www.tekton.com/1-4-inch-drive-dual-direction-click-torque-wrench-trq21101

While 10 in-lb is the lowest major increment, with the vernier has 1 in-lb markings and you can go a bit lower than 10. Of course it will start to lose accuracy at say 6 in-lb but I don't think that matters much in this application.

That should work. On my non-digital torque wrench, the click gets very faint at the lower limit. I looked up the specs on my digital torque wrench and realized the lower limit is actually 12 in lbs not 21 like I had said. I used the lowest value when tightening the nuts on my compression pack, so it must have been 12, not 21.

 

[SuperShort]

What would be perfect is a separator that deforms to fill the gaps, but I'm thinking that would need something that collapses at a specific pressure close to 17psi but can maintain pressures lower than that. I thought about neoprene sheet, but my experience of that is it looses it's spring too quickly. And it's an insulator, so negates my aluminium separator plates.

Make a mold in some sand, put a plastic saran wrap, then pour in a little clear epoxy for a perfect fit spacer.

Crystal Clear Bar Table Top Epoxy Resin Coating for Wood Tabletop - 1 Gallon Kit: Amazon.com: Industrial & Scientific

Crystal Clear Bar Table Top Epoxy Resin Coating for Wood Tabletop - 1 Gallon Kit: Amazon.com: Industrial & Scientific

www.amazon.com

I think two boards with this small innertube would allow measuring PSI.. I'm guessing 0%-100% charge size difference wouldn't make much of a difference in pressure since it's such a small relative distance.

Amazon.com

edit: this one looks better for this use.

Amazon.com: (Set of 2) 200 x 50 Inner tube (8"x 2") Innertube with angled stem for 8" wheel tire Merits Travel-Ease Commuter Heavy Duty (P182/(Set of 2) MP-1 U) : Automotive

Buy (Set of 2) 200 x 50 Inner tube (8"x 2") Innertube with angled stem for 8" wheel tire Merits Travel-Ease Commuter Heavy Duty (P182/(Set of 2) MP-1 U): Inner Tubes - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com