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

I recommend making an attempt to measure the compression set of your silicone buds. Crush them some known amount, and leave that crushed system in say ~100degC environment (this is to simulate the thermal kinetics of a few years passing) for a week, then allow to cool to room temperature, release clamp load and measure how much of its original thickness recovers immediately following the release of clamp load.
 
parabellum said:
Different sizes available.
They are precut, but sticky as hell and you want to have them in right place the first time.

Oh I don't like sticky. I'm just going to follow the proven route and get the mcmaster.com poron foam, given the cost is negligible per pack. I'm really excited about this pack build, I just don't have the BMS details worked out, or the funds to justify pulling the trigger on buying all the materials.

I would like to build up a couple packs for other people, but I don't feel confident doing that until I've used one I've built and put it through some heavy testing for several months.
 
liveforphysics said:
I recommend making an attempt to measure the compression set of your silicone buds. Crush them some known amount, and leave that crushed system in say ~100degC environment (this is to simulate the thermal kinetics of a few years passing) for a week, then allow to cool to room temperature, release clamp load and measure how much of its original thickness recovers immediately following the release of clamp load.
Yeah, I see where you are pointing to, I made more digging and there are a lot of different composition of silicon rubber, compression set can be somewhere between 3% and 70%. :| Have no 100C for 1 week available, but did compress it to 50% at 30-35C ambient we have here, will wait for a month to see what happens. What if I cycle the temperature few times? Is 100C and 35C big difference for material with such temperature stability? (-50C to 300C)
quuxman said:
Oh I don't like sticky.
They are sticky on the base only, but poron is definitively better choice, I just wanted to have it as transparent as possible to say hello now and then to every cell, every conductor. :D
 
Great idea. Thank you for sharing it with us. I was looking for a way to assemble the pack overseas where I would take everything but batteries, and it looks like this is it. I will be taking my bike to Japan for vacation, so once I build the case, I can just buy the batteries in Japan, pop them in, and I will be on my way zooming around the island of Shikoku. I just ordered ten 5x6 cell spacers on Amazon for only $8.19 including shipping.
 

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parabellum said:
I will use silicon bumps. :D About BMS, I am searching myself for one that stops and balances to ~4.1V/cell, only exotic stuff there ($$$).

After days of searching for a simple BMS with adjustable or 3 and 4-4.1 LVC and HVC respectively that did balancing before 4.2V, I concluded there are none. This is the only thing that's readily available and will definitely do the job, about $150:

https://www.energusps.com/shop/product/battery-management-system-bms-s516-30a-16

I'd like to hear how the bumps work out too.
 
Nice one, I believe it is circuit's creation, unfortunately 300USD for me, I need 24s (2x are required). Exotic and has to much stuff I do not need, BMS that is not killing my cells is good enough for me. I simply need 3V/cell LVC and 4.1V/cell HVC, even balancing is not so important.
 
I just bought a used Tesla battery pack and going to build e-bike pack from it.
How is your no solder/weld pack working for you? Any problems with connections or power flow?
Tesla pack.JPG
Tesla battery.JPG
 
spinningmagnets said:
How many cycles/miles/hours on that pack?
It is out of a 2015 P85D with 4,109 miles on it.
They should be OK. If not I will make earrings out of them and sell them on QVC. :lol: :lol: :lol:
 
I'm guessing this vehicle was in a wreck or something?

Before you disassemble, and then as you disassemble, and you PLEASE get some detailed macro shots of whatever cell corrosion and coolant line damage shots you can provide?

Thanks! I love Tesla and the incredible pack they designed!
 
parabellum said:
liveforphysics said:
I recommend making an attempt to measure the compression set of your silicone buds. Crush them some known amount, and leave that crushed system in say ~100degC environment (this is to simulate the thermal kinetics of a few years passing) for a week, then allow to cool to room temperature, release clamp load and measure how much of its original thickness recovers immediately following the release of clamp load.
Yeah, I see where you are pointing to, I made more digging and there are a lot of different composition of silicon rubber, compression set can be somewhere between 3% and 70%. :| Have no 100C for 1 week available, but did compress it to 50% at 30-35C ambient we have here, will wait for a month to see what happens. What if I cycle the temperature few times? Is 100C and 35C big difference for material with such temperature stability? (-50C to 300C)
I did have some time today and took out the silicon bump out of the vice.
Original thickness - 4mm
Compressed to - 2mm (50%)
Decompression after 1,5 month (almost)
In 5 seconds - 3.3mm (It was adhered to the vice with sticky base and took few secs to rip off)
In 1 minute - 3.6mm
In 5 minutes - 3.7mm
In 15 minutes - 3.8mm (most of the glue stood on the vice, so real end result could be little more)
Does it mean ~30% set rate? I took 5 sec result, am I doing something right, at least? Any advise? Is it good enough to use as compressing element for the cells?

P.S. Sorry, here is a picture :)
 
Great job on this - and thanks for sharing your ideas and techniques with the rest of us.

A kit to do this (minus cells) for a reasonable price would be game changing for home built ebikes. I just completed 2 simple bikes using ebay kits for which I built the battery packs out of 18650 cells - and that was by far the most time consuming, technically involved, and aggravating part of the whole project to do.

Now that it's done I wish I could start over and do it a little bit differently - but my expensive cells are all welded together.
 
Punx0r said:
3.8/4.0 = 95% of original thickness. So 5% set after 45 days at ambient when compressed by 50%.

So what can you/we say about this? Good or bad choice of material?

I would like to use something like this because I want to use a copperplate and not strips and this would hold things in place. When I cant use the spacer block grooves like snath is doing.
 
Swe said:
Punx0r said:
3.8/4.0 = 95% of original thickness. So 5% set after 45 days at ambient when compressed by 50%.

So what can you/we say about this? Good or bad choice of material?

I would like to use something like this because I want to use a copperplate and not strips and this would hold things in place. When I cant use the spacer block grooves like snath is doing.


It's not bad at all for compression set if your design keeps it at say 30-40% crush, and it only loses ~5% of it.

It will likely be fine under increased temps as well being a silicone, but I would recommend doing your compression set tests at an increased temperature. For every ~10degC you increase it, you've doubled the rate of thermal-kinetic processes deforming the polymer. For this reason, if it's a high temp material like silicone, you could elevate it to say 90degC for a week and simulate years of compression set effects.
 
liveforphysics said:
It will likely be fine under increased temps as well being a silicone

Would Polyurethane be a bad choise? I saw these bumbers in that material. Looks like they have a nice shape but not silicone:
http://www.ebay.com/itm/200pcs-Adhesive-Rubber-Feet-Bumper-Stops-Door-Cupboard-Drawer-Cabinet-Kitchen-/112113767958
 
Over two years and still nobody is making these to sell?

I accept that over time, alternative parts can be sourced that "may" improve some part, but...I feel this is very workable in its present form. I had hoped that maybe I could have started to produce these, at least until a real manufacturer began producing them (I have a full-time job).

I have an "open source" idea I haven't seen published yet, so I want to post it here and that way, anyone who wants to use the idea can point to the date on this post to show date of origin. I have contemplated a loose-cell box for quite a while. I am satisfied with the current state of this design, and Snath has encouraged me to produce it, and for anyone on ES to produce it. The one area where I have reservations is in...which way should the P-group cells face?

Should they alternate the positive ends of each P-group? (that way the connecting bus bars are compact and short. Or...should all the cells face the same way? Of course in the second configuration, the bus-bars will need to connect the top of one P-group to the bottom of the adjacent P-group. It would require the bus bars to have a shape like this:

xxxxxxx........ (dots are cells, X's are bus bar)
__..__x........
........x........
........x........
........x__..__
........xxxxxxx

Plastic forms in the cell separators would prevent the odd-shaped bus bars from being installed incorrectly by various means.

Whether the P-groups all face the same way, or alternate, my "Idea" is to have a nipple pressed into the bus bar where it faces the positive cathode button (just as Snath has done), but on the flat negative anode end, there is a hole in the center of the bus bar contact point, so a cell facing the wrong way will not make contact with the bus bar. The negative ends of the cells would have a contact with the bus bar that looks like a ring, provided by a larger diameter "button" pressed into the bus bar, and then a hole drilled into the middle). The positive end of the bus bar would have a small button that had the same diameter face as the positive button on the cell.

I would also color the insides of the P-group compartments so it would be even more obvious which way that cell-group should face. If assembled incorrectly, it would be an open circuit.

I know this "idea" needs some work, but I think it has some potential. Feel free to use this if it appeals to you.
 
How do you connect the thick positive and negative leads to the copper strips? Do you just lay the copper wire on the strip/plate and just add a lot of solder? Is that enough for it to not loosen?

Tried to search for this but cant find anything related and since you have to do this on a snath pack I guess I can ask here.
 
Swe said:
liveforphysics said:
It will likely be fine under increased temps as well being a silicone

Would Polyurethane be a bad choise? I saw these bumbers in that material. Looks like they have a nice shape but not silicone:
http://www.ebay.com/itm/200pcs-Adhesive-Rubber-Feet-Bumper-Stops-Door-Cupboard-Drawer-Cabinet-Kitchen-/112113767958


Really must test compression-set if it's a material that doesn't have a good datasheet. My hunch would be that those would creep. Some urathanes are urathane/urea hybrids and have some visco-elastic creep, which means clamp load on your joints approached zero over time.
 
Luke, what are you thoughts on Rogers Bisco HT-800 silicone?
https://www.rogerscorp.com/documents/452/ems/bisco/HT-800Medium-Cellular-Silicone.pdf
https://www.rogerscorp.com/documents/477/ems/bisco/Compression-Modulus-of-Cellular-Silicones.pdf
I want to use it on my battery kit. I have got samples cut out of Rogers Poron 4701-40, i think it is the same Snath used on hes batteries and it feels fine. I have FSR under compression to measure the force for 7 months now and readings did not changed a bit.
upload_-1.jpg

Guess Bisco HT-800 would be even better with lower compression set(<1% vs. <5% @ 70C) and wider working temperature band.
 
agniusm, I think those bus-plates are wonderful, thanks for posting them. I do have one suggestion. The small finger that sticks up at the top center, the part that the slide-on connector attaches to? I would make it "T" shaped. I would slide a steel crimp sleeve over a wire that has a stripped tip. Lay the bare copper strands from the wire-tip onto the center of the copper "T", fold over the two arms so that the T is now an "I". Then slide the steel crimp sleeve over the folded copper arms and crimp it down.

The copper would carry the current, and the steel crimp sleeve would provide long-lasting clamping force. I haven't tried this yet, so I don't know what issues might come up, but...just a thought.

edit: unless, of course, that connection is only for the low-current balancing wire. In that case, I'm sure it will be fine.
 
agniusm said:
Luke, what are you thoughts on Rogers Bisco HT-800 silicone?


It looks great on a datasheet, as to most silicones.

I personally avoid silicones when possible, due to crack-propagation and notch-sensitivity, meaning an otherwise tough and robust piece of silicone (or glass which is basically the same building blocks as silicones), can get a tiny surface scratch, and now the crack propagates right through the whole material (glass or siloxane polymers alike). The other funny thing silicones do is transport vapors through them though they seal liquids fine, they are not gas barriers (may or may not matter depending on pack and application). They also tend to be awful to get finished polymerizing siloxane surfaces (like silicone sheets) to bond with adhesives to anything well enough to stay located in situations where the clamp loading alone can't control the position of the material from extruding out and escaping it's clamp loads over time.

I do still use silicones once in a while (sometimes it is the best option for the application), but typically only as a last resort if no other material is suitable due to the above material issues.
 
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