Another No Solder/Weld 18650 Build (Updated 03/09/2014)

[snath]

Awesome idea, great build!
Here is my 2 cents in the picture...

HAND DIMPLING.jpg

Waiting for spacers 12s8p but cannot buy closedcell compressing foam... Can someone send me stripes for my battery in envelope? I am in EU. PM

Thank you
opzopus

Nice job. Should work fine.

You may wish to use a 'washer-head" screw to control dimple depth. In use, the flange on the screw head in contact with the washer under the strip would ensure dimples of the same depth.

Flange head screw images here: https://www.google.com/search?q=washer+ ... 10&bih=602

[Pat Eaton]

I have my spacers and this weekend I will source some copper. I have some single konions from DrBass to experiment with.
I am also going try some different contact greases. My system is low draw at just over 1c so the contact issue should be minimal.

Always something to learn and experiment with.

[parabellum]

Can small N52 magnet behind cooper strip generate needed pullforce?

[snath]

I have my spacers and this weekend I will source some copper. I have some single konions from DrBass to experiment with.
I am also going try some different contact greases. My system is low draw at just over 1c so the contact issue should be minimal.

Always something to learn and experiment with.

I got some of this NYK Anti-Corrosion stuff from our own Big Moose: http://mtg-technologies.com/zencart/ind ... ucts_id=12

[snath]

Can small N52 magnet behind cooper strip generate needed pullforce?

I would stick with the foam. The magnet will not provide any cushioning effect.

I experimented with a lot of techniques and the foam was the best I came up with.

That is not to say that different ideas won't work...... Look at the nifty dimpling tool that opz.EST came up with.

However, for those who are having trouble sourcing Poron/urethane foam, you might try office-type rubber bands. You can get them in widths that are very close to the slot size in the spacers (or trim them to fit). You will have to shorten your spacer bars and sides to account for the fact that they are only about 1/32" thick but still will want around 20% compression. If you go this route, you will want to check them periodically for dry rot; that's the big downside to using natural rubber.

[opz.EST]

What you guys think about silicone sealant caulk `worm` used in bathrooms. May last long and should be used in various thickneses...

[snath]

What you guys think about silicone sealant caulk `worm` used in bathrooms. May last long and should be used in various thickneses...

Might work if you can obtain uniform thickness somehow

[jayx]

Brilliant design, actually I was thinking about something similar just was going to use wave springs. But foam solution seems to be easier and cheaper, the only problem is availability outside the US. Also it looks like at such low thickness of the foam, case needs to be made very precise otherwise compression will be too high/too low. Another thing - are case top & bottom stiff enough to maintain the same distance when cells are inserted? I would expect it to bend in the middle.

[snath]

Brilliant design, actually I was thinking about something similar just was going to use wave springs. But foam solution seems to be easier and cheaper, the only problem is availability outside the US. Also it looks like at such low thickness of the foam, case needs to be made very precise otherwise compression will be too high/too low. Another thing - are case top & bottom stiff enough to maintain the same distance when cells are inserted? I would expect it to bend in the middle.

The case ends, bottom, and spacer bar(s) need to be cut pretty closely (2.72ish inches). This will allow for adequate compression and the spacer bar(or bars depending on how many cells you are using) prevents the sides from bowing.

[Pat Eaton]

2.72, hmmmm my batteries and spacers measure 2.82 how much wider is the case than the batteries and spacers?
1/16"?

[snath]

I'm roasting coffee and am away from my battery making stuff.
Let me finish up here and I'll go check my dimensions and make sure what I said was correct.

[Pat Eaton]

Mmmm thanks I'll have a cup.

[snath]

2.72, hmmmm my batteries and spacers measure 2.82 how much wider is the case than the batteries and spacers?
1/16"?

Ok, I measured a leftover spacer and it is 2.70 inches (somewhere in the range of 2.68 to 2.72 will work fine). This will correspond to the inside/width of the battery case. You have to ignore the four little tabs on the spacer that hang over the ends of the cell. The bus bar and the compression strip fit between them.

[jayx]

2.72, hmmmm my batteries and spacers measure 2.82 how much wider is the case than the batteries and spacers?
1/16"?

Ok, I measured a leftover spacer and it is 2.70 inches (somewhere in the range of 2.68 to 2.72 will work fine). This will correspond to the inside/width of the battery case. You have to ignore the four little tabs on the spacer that hang over the ends of the cell. The bus bar and the compression strip fit between them.

I think different cells may slightly vary in length so probably better to measure them and calculate required case inner dimensions (add compressed foam/busbar/slip film thickness).

[jayx]

Another question to Snath & Liveforphysics - you've mentioned a few times PVC will be better, could you let us know why? What about polycarbonate, I've heard it's good.

[snath]

Another question to Snath & Liveforphysics - you've mentioned a few times PVC will be better, could you let us know why? What about polycarbonate, I've heard it's good.

PVC is really tough stuff..... much more so than the acrylic that I made this case out of and it's what I used for the build that is linked to the top of this post. I'm using polycarbonate for a build that I'm currently working on because, as LFP pointed out, acrylic is not very tough and is pretty brittle. Polycarbonate has better strength, not as good as PVC but I can get it in clear in thicknesses that I want. I'm ok with polycarbonate I think it's cool to be able to see inside my battery

[snath]

2.72, hmmmm my batteries and spacers measure 2.82 how much wider is the case than the batteries and spacers?
1/16"?

Ok, I measured a leftover spacer and it is 2.70 inches (somewhere in the range of 2.68 to 2.72 will work fine). This will correspond to the inside/width of the battery case. You have to ignore the four little tabs on the spacer that hang over the ends of the cell. The bus bar and the compression strip fit between them.

I think different cells may slightly vary in length so probably better to measure them and calculate required case inner dimensions (add compressed foam/busbar/slip film thickness).

Good idea.

BTW, the slip film gets pulled out after the cells are inserted. It just helps to prevent the foam from rolling up when you are stuffing the case.

[jayx]

Good idea.
BTW, the slip film gets pulled out after the cells are inserted. It just helps to prevent the foam from rolling up when you are stuffing the case.

I thought you leave slip film so it's also easy to remove batteries if required.

PVC is really tough stuff..... much more so than the acrylic that I made this case out of and it's what I used for the build that is linked to the top of this post. I'm using polycarbonate for a build that I'm currently working on because, as LFP pointed out, acrylic is not very tough and is pretty brittle. Polycarbonate has better strength, not as good as PVC but I can get it in clear in thicknesses that I want. I'm ok with polycarbonate I think it's cool to be able to see inside my battery

I thought polycarbonate is the most tough transparent material you can get, didn't even know transparent PVC exist . Anyway I'm not sure polycarbonate can be easily solvent weld or bond.

[Overclocker]

I have my spacers and this weekend I will source some copper. I have some single konions from DrBass to experiment with.
I am also going try some different contact greases. My system is low draw at just over 1c so the contact issue should be minimal.

Always something to learn and experiment with.

a supplier gave me a tub of this. can't comment on its performance though...

[snath]

Good idea.
BTW, the slip film gets pulled out after the cells are inserted. It just helps to prevent the foam from rolling up when you are stuffing the case.

I thought you leave slip film so it's also easy to remove batteries if required.

PVC is really tough stuff..... much more so than the acrylic that I made this case out of and it's what I used for the build that is linked to the top of this post. I'm using polycarbonate for a build that I'm currently working on because, as LFP pointed out, acrylic is not very tough and is pretty brittle. Polycarbonate has better strength, not as good as PVC but I can get it in clear in thicknesses that I want. I'm ok with polycarbonate I think it's cool to be able to see inside my battery

I thought polycarbonate is the most tough transparent material you can get, didn't even know transparent PVC exist . Anyway I'm not sure polycarbonate can be easily solvent weld or bond.[/quote

Polycarbonate can be easily solvent bonded. I'll use the same stuff that I used on the acrylic. Don't remember the name but I mentioned it somewhere above...... or, simply do an internet search.

[Gab]

how is pack holding up ?

whats the max current you think is safe going through each cell ? the copper nipple provides a nice big flat surface but how much power is too much ? i.e is 5 or 10 amps to much for this type of join ? for less then this I cannot see any problem.

[snath]

how is pack holding up ?

whats the max current you think is safe going through each cell ? the copper nipple provides a nice big flat surface but how much power is too much ? i.e is 5 or 10 amps to much for this type of join ? for less then this I cannot see any problem.

The pack is holding up well. I really like it, the hard case, rounded corners, etc. make it really easy to use in the application I made it for (stuffing in a fanny pack).

A don't have any idea what the max current would be for this type of cell to contact interface. Perhaps some of our engineering types would like to opine?

[agniusm]

Hey mate. Could you give some info on the foam you have used, linky would be nice. Also, what size dimples you have made, depth and diameter? Went through the thread and missed this info

[snath]

Hey mate. Could you give some info on the foam you have used, linky would be nice. Also, what size dimples you have made, depth and diameter? Went through the thread and missed this info

The copper is .010" thick. The dimple punch is .187" and the die plate is .040" thick with .0218" holes.

I got my foam from McMaster Carr Part No. 86375K132 . Link: http://www.mcmaster.com/#catalog/120/3572/=s253rm .

[agniusm]

Thanks. Is there a reason for that particular foam? I see there ones that are firm with 20+ psi. I have not dealt with these foams and therefore thought bigger is better:) could you elabotare on this foam stuff ad psi, bounce back parameters?
Cheers