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

[snath]

HOLY WATTHOURS BATMAN!! IT'S, IT'S, ANOTHER SNATH PACK!!

In this previous post http://endless-sphere.com/forums/viewto ... 14&t=57008 , I detailed a pack build that required no soldering or welding of the cells. Based on some of the comments and a desire to improve the build, I promised to create a more simple build. Here it is.

View of one side and end of the pack. Note only one spacer bar. The pack is 10s5p of Panasonic PF cells that I got from Orbtronic. It measures 8 1/4 x 5 x 3 inches and weighs 6.4 pounds.

Side View.jpg (13.79 KiB) Viewed 22111 times

Wheeeee! Only one screw per side!! (and three holding the top on.)

The pack is based on 18650 spacer blocks, formed bus bars (.308 wide x .010 thick), compression blankets (one for each side of the pack), and a solvent welded acrylic case.
The 186450 spacer blocks are pretty self evident so lets begin with the formed bus bars.

The dimpling block is made of two pieces of 1/2 x 2 x 4 inch cold rolled steel. The length is important because it establishes the length of the bus bar and critical bends and folds as noted below. Note: this the only part that requires much beyond hand tools. However, after having made a couple, one could make it out of clear plastic and instead of machining a groove to position the bus bar blank, simply scribe a line at the proper distance from the centerline of the dimple punch holes and use it to visually position the blank.

Dimpling Block.jpg (13.24 KiB) Viewed 22111 times

The dimples are made with a couple of light taps with a hammer on the punch.

Here are the two block halves, the 3/16 inch punch and the die plate of .010 inch sheet with .220 inch holes.

Dimpling Block Parts.jpg (12.69 KiB) Viewed 22111 times

Here's the block with a completed bus bar half. On the left is a 5/16 tab that is bent down. This tab hooks onto the bottom of the spacer blocks and holds the bars in place when loading the pack into the case. I also used a dot of double sided tape under each tab to keep them secured in location. The first punch hole in the die block is place 10 mm from this end. all the other holes are 20 mm apart. This leaves a little extra (1.6 mm) to provide clearance over the tops of the spacer blocks for the folded solder tab (20 mm before folding)

With Completed Bus Bar Half.jpg (13.29 KiB) Viewed 22111 times

Here are a pair of bus bar halves with mated solder tabs located in the spacer block grooves. Note that the solder tabs must be bent one right and one left to properly mate up.

A Pair of Bus Bars With Mating Solder Tabs.jpg (13.98 KiB) Viewed 22111 times

Using the Spacer Blocks as a Soldering Fixture.jpg (13.94 KiB) Viewed 22111 times

I made the case of 1/8 inch acrylic using traditional score, break, solvent weld techniques. I made the case to fit in a fanny pack but in anticipation of wishing to hard mount it, I epoxied some 80-20 Tee nuts inside the case.

The Acrylic Case.jpg (8.46 KiB) Viewed 22111 times

Loading it Up .jpg (14.46 KiB) Viewed 22111 times

I drilled a 1/4 inch hole in each spacer block assembly for the spacer rod and used those holes and a little hollow punch to punch the corresponding holes in the compression blankets.

One of Two Compression Blankets.jpg (7.68 KiB) Viewed 22111 times

I added dots of double sided tape to hold the compression blankets in place. If you look closely, you will see similar dots under the "hooks" on the bus bars.

Compression Blanket Folded Back to Show Dots of Double Sided Tape.jpg (11.66 KiB) Viewed 22111 times

These worked very well.

Slip Sheets of Photocopy Transparency Film.jpg (10.05 KiB) Viewed 22111 times

Stuffing The Case.jpg (12.09 KiB) Viewed 22111 times

Of the completed case. Note that the solvent works very well to glue the Anderson connectors in place.

Top View.jpg (15.19 KiB) Viewed 22111 times

End View.jpg (13.62 KiB) Viewed 22111 times

Note in the end view that I trimmed the engagement tabs off the spacer block assemblies and left the tabs on the fabricated top extra long to lock the assembly in place and keep it from moving vertically. Also, note that the compression of the Poron foam blankets is set by the width of the sides and the length of the one spacer bar. I cut mine so that the foam would be compressed about 25%.

In the fanny pack

In The Case.jpg (12.41 KiB) Viewed 22111 times

Front of the fanny pack that I got at REI. Note the very excellent Icecube57 precharge dongle... figured I would need it as I would be plugging and unplugging a lot.

Case Front.jpg (13.14 KiB) Viewed 22111 times

So, there you have it, a simple no solder/weld 18650 battery pack.

Updated 03/09/2014

I replaced the compression blanket with 5/16 compression strips. I think they work better plus, you get to see the ends of the cells. Sexy huh?

Compression Strips.jpg (14.66 KiB) Viewed 21454 times

_________________________________________
moderator edit to add these links (with permission from snath):

"yet another solderless DIY battery pack via NIB's" (using magnets to hold busses against the cell tips)
http://endless-sphere.com/forums/viewto ... 14&t=60517

Solderless compression pack, square PVC fencepost, ES member Idlemind
viewtopic.php?f=14&t=69738#p1078812

"18650 battery Kit development and discussion" (agniusm, 4 pages)
viewtopic.php?f=14&t=63190&start=75#p1153660

"18650 pack build using plastic battery holders" (from http://www.recumbents.com, 4 pages)
viewtopic.php?f=14&t=72138

"DIY assembly kit for 18650 without spot welding/Soldering" (VRUZEND, 8 pages)
viewtopic.php?f=31&t=87434

"N.E.S.E. the no solder module" (Agniusm, 2 pages)
viewtopic.php?f=31&t=88051

[liveforphysics]

I'm not a fan of acrylic and would have used clear PVC or something, but you rock man!! Your interconnect system is tits!!! I love it!!

[Tench]

The way you have taken the comments from the ES about your other build and created this one is what this place is all about, Well done!!
I liked the concept and some of the methods in the first one but this one is so much better!! You should make the components available as a kit!
You need to make a rotary dimpling tool now so by cranking a handle you can dimple a whole roll of copper, and can I have a 20s7p kit please!

[snath]

I'm not a fan of acrylic and would have used clear PVC or something, but you rock man!! Your interconnect system is tits!!! I love it!!

I love PVC! Worked in a plating shop once..... we made all kinds of equipment out of the stuff. But, while PVC would have indeed been a better choice, in the interest of using pretty much all hand tools, I chose acrylic because you can score and break it.

Again, thanks for your nice comments on the interconnect system. It really is simple and easy to do. And the beauty of it is that you are not locked into a particular build. Want a 12s pack? Make another case, take out the cells and reconfigure them!!

[snath]

The way you have taken the comments from the ES about your other build and created this one is what this place is all about, Well done!!
I liked the concept and some of the methods in the first one but this one is so much better!! You should make the components available as a kit!
You need to make a rotary dimpling tool now so by cranking a handle you can dimple a whole roll of copper, and can I have a 20s7p kit please!

Thank you for the compliments. I really like the KISS concept. Or, in the, loftier parlance of the manufacturing world, Continuous Improvement.

Mmmmmm, maybe I could make it so that it would cut the strips too It was a bit of pain to get the strips .310ish wide But, I just clamped them up between a couple of pieces of wood and filed the edges parallel. No big deal really.

You could make a 3-hole dimpling block that would make as many "p" as you would like, just make three dimples and then index the strip along 2 dimples engaged and one to punch until you have as many dimples as you need and then snip the end off at 20mm and fold it.

[r3volved]

Awesome work!
Definitely saving this for later.

So do you like the second build better than the first? We're the comments and changes beneficial? Anything you would change on a v3?

[spinningmagnets]

Excellent job, and wonderful pics documenting this. I'm sure the connections are adequate, and the compression foam allows for heat expansion/contraction, but I was wondering a few things:

Is there a conductive paste that could be put between the dimples and the cell-end to ensure good contact and preserve a lack of oxidation at that point over time? Copper doesn't "rust" but it still forms a thin layer of oxidation that would change the resistance over time (possibly negligible at it's worst?)

I've heard closed-cell foam doesn't lose its "sponginess" over time (for at least the 3 years that I would imagine is the life of a pack like this). What is a good supplier and what is the best type of closed-cell foam to make the compression blanket?

edit: helpful links added below

http://ntsworks.com/over-the-hill-on-an ... elicio-us/

"Conductivity improving grease project"
http://endless-sphere.com/forums/viewto ... 14&t=61542

"Yet another solderless DIY battery pack via NIB's" by radad, 7 pages, using magnets to keep copper strips in contact with electrodes
http://endless-sphere.com/forums/viewto ... 14&t=60517

"One more no “solder”, no tools, no skills, 18650 pack build" by parabellum, 3 pages, boxy plastic cell holders apply coil-spring pressure on electrodes, current flows through separate copper strips.
http://endless-sphere.com/forums/viewto ... 14&t=66555

"Need help designing triangle pack, 18650 cells" spinningmagnets, one page, grouping 5P strings using only two basic module shapes.
http://endless-sphere.com/forums/viewto ... 14&t=48342

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

When it comes to low cost, ready availability, and high performance, there is no competition, copper is the way to go. that being said, there are concerns for builders in seaside communities where the air is humid and salty. This leads to corrosion on the copper (the green cancer). Pure nickel is very resistant to corrosion of this type, and when using copper busses, they can be nickel-plated or zinc-plated without degrading the current-carrying capabilities of the bus very much.

That being said, if you don't want to fuss with making copper busses and then plating them, another option is red brass or yellow brass. When it comes to current-carrying ability and corrosion-resistance, the brasses are between nickel and copper. Brass is readily available and very cheap, so...even though it is difficult to spot-weld onto cell ends, it is a very viable material when we are considering pressure-contacts, like the contacts shown here. Since yellow-brass has a conductivity of 28/100 and nickel is 22/100, that is roughly a 6/22 improvement, or 27% better. This also means you only have to make the bus with 1.6 X the area to double the current.

7mm X 0.20mm nickel-strips are common, 28-ga yellow brass is 0.30mm thick.

[snath]

Awesome work!
Definitely saving this for later.

So do you like the second build better than the first? We're the comments and changes beneficial? Anything you would change on a v3?

I'm pretty happy with this one but if you have access to a table saw, I would, as LFP suggested, use PVC.

[snath]

Excellent job, and wonderful pics documenting this. I'm sure the connections are adequate, and the compression foam allows for heat expansion/contraction, but I was wondering a few things:

Is there a conductive paste that could be put between the dimples and the cell-end to ensure good contact and preserve a lack of oxidation at that point over time? Copper doesn't "rust" but it still forms a thin layer of oxidation that would change the resistance over time (possibly negligible at it's worst?)

I've heard closed-cell foam doesn't lose its "sponginess" over time (for at least the 3 years that I would imagine is the life of a pack like this). What is a good supplier and what is the best type of closed-cell foam to make the compression blanket?

There are conductive greases available. In a past life, we used some stuff called "stab grease" on high voltage contacts. Vaseline will work too.

I got may foam from McMaster Carr. Here's the Part Number and description: 86375K132 Quick-recovery Super-resilient Foam, Plain Back, 1/16"thk, 12" X 12", Extra Firm .

[liveforphysics]

For the conact interfaces, take this:

http://www.us-nano.com/inc/sdetail/4509

And blend with just enough of this to make it grease - like instead of powder:

http://www.ebay.com/itm/271416859954?redirect=mobile

I would imagine you've already got extremely low interconnect resistance, but this would make it even lower and able to stay that way.

There is a product you can buy that is already made up with CNTs in a grease, but it's like $80/gram and you can make a batch of like 10g (enough to do dozens of batteries if you're using it right) for under $250.

Load it in a little syringe and just dab a few mg onto each contact point. You could surround it with regular compound #70 for weatherproofing/moisture/oxidation etc.

[dogman dan]

Definitely looks real good to me. Well Done!

So what if you end up having to replace the foam annually. Since it's all parallel connections on the dimples, one flaky cell here and there won't murder you. Not like the series stacked idea where one bad contact screws you.

[liveforphysics]

There are foams you would never need to replace. They have about 10% initial compression set, and even after decades they will hold the remaining clamp load.

Poron is pretty damn good already though.

[999zip999]

I want to hold it in my hands.

[spinningmagnets]

Awesome links Luke! Thanks for posting that. The conductive grease (only a very tiny dab per cell end) is likely to be un-necessary, but it would boost my confidence that the electrical connections would remain solid over time.

The only soldering needed would be to connect the bus bar ends to main pack power wires, and that would be done without cells in their positions, so there is never the slightest danger to the cells from heat.

[granolaboy]

This is why I love this forum. Every now and again someone comes along and comes up with something truly brilliant and ground breaking.

Awesome job dude! Would love to see kits for sale

[footloose]

You should make the components available as a kit!

+1

Really elegant design.
For laughs I took a look at my own most recent battery build.
Yeah, sure, it works, but... not pretty. I'm not going to post photos

Seriously, while people could build their own manual bus-bar "stamping press" based on your generously documented design... why not knock out a bunch of bus-bars in various lengths and offer them for sale? Smallish market probably, but count me in.

[www.recumbents.com]

Snath - did you get the copper strip at Mcmaster.com too? What size?

[snath]

Snath - did you get the copper strip at Mcmaster.com too? What size?

I'm using leftovers from an 18" x 10' roll of 10mil (.010 thick) that I got from this place http://basiccopper.com/10-mil-010-inch-.html to cover a countertop for a wood fired pizza oven that I made.

McMaster Carr does have it but choices of length are a bit more limited so prices are higher. http://www.mcmaster.com/#standard-red-m ... ts/=qyaczy

A 1" wide strip will get you three bus bars with careful cutting.

[spinningmagnets]

I really like this design. I would want bolts to hold the two sides together that didn't protrude out very much. I'd like them smooth if possible with a hex socket. I know I can have the two sides connected by a threaded coupling nut (looks like a normal nut but longer), but I thought it would be easier to use threaded rod (thin, cheap and readily available in common thread-sizes). So...I've been looking for an odd nut that uses a hex socket but has a very flat head that could sit down inside a thin "spot-face" depression. I found it, they are called "furniture nuts":

NutsFurniture.png (109.71 KiB) Viewed 21683 times

NutCoupling.jpg (9.34 KiB) Viewed 21683 times

[snath]

I really like this design. I would want bolts to hold the two sides together that didn't protrude out very much. I'd like them smooth if possible with a hex socket. I know I can have the two sides connected by a threaded coupling nut (looks like a normal nut but longer), but I thought it would be easier to use threaded rod (thin, cheap and readily available in common thread-sizes). So...I've been looking for an odd nut that uses a hex socket but has a very flat head that could sit down inside a thin "spot-face" depression. I found it, they are called "furniture nuts":

NutsFurniture.png

NutCoupling.jpg

I don't see much wrong with the flat head screws i'm using. They don't protrude at all. In fact, they are inside the case.

I think you don't understand how the spacer bar (along with the width of the sides and bottom) establishes the amount of compression on the foam. I think it would be difficult to accurately set (and maintain) compression with what you are proposing.

However, different ideas and experimentation are what makes this fun.

[snath]

I really like this design. I would want bolts to hold the two sides together that didn't protrude out very much. I'd like them smooth if possible with a hex socket. I know I can have the two sides connected by a threaded coupling nut (looks like a normal nut but longer), but I thought it would be easier to use threaded rod (thin, cheap and readily available in common thread-sizes). So...I've been looking for an odd nut that uses a hex socket but has a very flat head that could sit down inside a thin "spot-face" depression. I found it, they are called "furniture nuts":

NutsFurniture.png

NutCoupling.jpg

I don't see much wrong with the flat head screws i'm using. They don't protrude at all. In fact, they are inside the case.

I think you don't understand how the spacer bar (along with the width of the sides and bottom) establishes the amount of compression on the foam. I think it would be difficult to accurately set (and maintain) compression with what you are proposing.

However, different ideas and experimentation are what makes this fun.

In fact, why don't you build one and post it. I'm sure we all would really like to see it.

[r3volved]

YouTube the next build. Or at least the assembly.
That would eliminate a lot of questions.

[Punx0r]

Nice write up. Very informative

[snath]

I really like this design. I would want bolts to hold the two sides together that didn't protrude out very much. I'd like them smooth if possible with a hex socket. I know I can have the two sides connected by a threaded coupling nut (looks like a normal nut but longer), but I thought it would be easier to use threaded rod (thin, cheap and readily available in common thread-sizes). So...I've been looking for an odd nut that uses a hex socket but has a very flat head that could sit down inside a thin "spot-face" depression. I found it, they are called "furniture nuts":

NutsFurniture.png

NutCoupling.jpg

I don't see much wrong with the flat head screws i'm using. They don't protrude at all. In fact, they are inside the case.

I think you don't understand how the spacer bar (along with the width of the sides and bottom) establishes the amount of compression on the foam. I think it would be difficult to accurately set (and maintain) compression with what you are proposing.

However, different ideas and experimentation are what makes this fun.

In fact, why don't you build one and post it. I'm sure we all would really like to see it.

Woops, I don't even remember how the thing went together But then I have that first your hair, then your brain thing . Anyway, the screws are outside the case but countersunk so they don't protrude. They draw the sides of the case against the spacer bar to set the compression.

Sorry for the confusion.

[spinningmagnets]

You've done a wonderful job on this, and the pictures you have posted do a great job of explaining the idea. This thread link is definitely saved by me. Sharing the details of how to make one of these is a great service to the E-bike community.