xeris

Have been fooling around with assembly of a Li-ion battery. Uses the ubiquitous 18650 cell Previously I had tried to solder the bus bars to the cells with results that I didn't like. The big difference in pack design (for me) was the discovery of the spacers Battery Spacers, Separators : Lithium Rechargeable Batteries, Battery BMS, Pack Assembling that allowed a non solder build. Found this site and thread https://endless-sphere.com/forums/viewtopic.php?f=14&t=57810
Picked up the poron blanket material here McMaster-Carr - Poron Urethane Foam
Thought it looked like a smart way to build a pack. Pack can easily be disassembled and any issue with a cell can be addressed. Cells could also be upgraded to what ever new, better cell that comes into the market. Found the cells here http://liionwholesale.com/
Also purchased some 26650 cells and spacers, but have not finished a pack using them yet.
Used two pieces of 1/8" PVC laminated together (1/4") to form top and bottom plates. During the glue up of the plates I built a bit of camber into the pieces. Discovered the need for the camber on my first experiment in building the pack using ~1/4" plexi for top and bottom plates. Probably could use a center screw to eliminate the bowing up in the middle of the plates, or other reinforcement on the plates. Might do that in a future build, but right now this is how it came out.
I thinking about draining the pack to ~14.2-4V. Not sure if the higher voltage the pack has now will cause a problem with the electrical components in the bike (converter unit, ICM?) Since that voltage is where the charging system is currently running at I know that is OK. The fully charged cells, 4.2V which yielded 16.8V for the pack. Have been testing the pack by cranking over the motor on a C70 Passport I have in the garage. Using that to reduce the voltage and check for any issues with the pack.
Some photos.

xeris

More photos.

Wolverine

And you have how much $$ wrapped up in this project?

xeris

The 18650 cells were $4.xx ea. ~$38.00ish. for eight. The spacers were pennies ea. Copper for bus bars, free. Steel for tool to dimple bus bars, free. Local machine shop $20 for milling the dado in the steel bus bar tool. Which can be used over and over and over and over again. Screws and misc. fasteners ~$3-4 beyond what I had in my 30 odd year old stash of same. The PVC and poron sheets were <$20. and are enough to make multiple packs.
The big advantage over buying a $100+ ready made Li-ion battery they can be repaired if a cell goes bad. I know what quality of cell the pack is comprised of, which is the biggest advantage as not all Li-ion cells are equal in quality.
Most important, to me, the same reason we wrench on our bikes, to make it mine.

NHSH

Respect!!! way to go, especially the fact you came up with a real solution to be able to maintain each battery individually with such ease. True engineering mind!

I been using the 8 pack shrink wrapped trough Daugherty for 4 years now successfully on the VTR, ton's of torque on every start, but wondered what am I going to do when it will start failing..

Also had a smaller 6 pack that I got at the same time that failed last year on my XR650 and was very disappointing. Partly my fault, I didn't upgrade the oem charging system which kinda suck, these batteries do like better charge than the old Honda diode crappy R&R can give.

Wolverine

+1.

E.Marquez

Nice take on a DIY battery pack...
Ive been making my own for a few years now. each battery gets a soldiered on tab.. the tabs connect by copper buss bar, the whole thing is shrink wrapped.
So i can still pull a battery pack apart to individual cell, and charge them / test them individually. I can balance individual cells or pairs. And if the day comes, replace an individual cell by removing the cell, soldiering the tab, and soldiering it onto new, charged and balanced cell.

I like the idea you came up with....
Are you concerned at all, you will have less than perfect contact between cells and the copper "buss bar" Vibration and shock is a huge factor in pack failure..
Is there a "springy" pad between battery and the end caps? that might help keep great contact between batter and the copper bar...

Overall size... does your pack end up same, larger? smaller then an OEM battery?

Because of the extra space between rows of cells in my packs to connect tabs the buss bar...my packs end up the same size as an OEM battery in width and length, just less in height. ..and a whole lot lighter of course.

xeris

I did not have good results with solder tabs/bus bars. In fact I killed 2 cells after two rounds of on and off with the bus bars. These were cells that I pulled out of a DeWalt battery pack I found on sale.
No joke there. As you know a short can make a big mess.
Since this is all experimental and I have not run it the bike yet, there is some question in my mind. That said, following the build design (more or less) from the Endless Sphere web site which emphasized the use of a urethane Poron sheet to hold the bus bars in place and minimize any vibration from causing a loss of clamping force.
With the thickness of the copper and depth of the dimple on the bus bar, the depth of the channel the bar fits into across the spacers I feel like there will be more than enough pressure on the cells.

The finished pack is roughly 78mm (3")HX42mm (1 5/8")WX100mm (4")L. This doesn't include the terminals. They protrude above the top plate about 19mm(3/4"). So quite a bit smaller than stock.

E.Marquez

How about contact paste? It would both prevent oxidation that would increase resistance and help ensure constant contact.
http://www.mgchemicals.com/products/...mbly-paste-847

The other concern I was having with the need for a "spring" layer is cell contraction / expansion while heating and cooling.

xeris

Thanks for link. Yes I have, but haven't done a search and this will save me a lot of time. That paste, I think, is the same that was mentioned somewhere in the thread on Endless Sphere site I linked to in my first post.
The post I remember contained some mention of the price. At $13 for 25mg, building a big pack, e-bike or similar would get into your pocket a bit. For what I'm doing, not so much.
Here is a place to purchase from MG Chemcials 847 Carbon Conductive Assembly Paste

The urethane Poron blanket is supposed to perform that function. I have had the pack assembled, sitting on my bench close to two weeks before I disassembled it and took photos. The Poron had some indents from the spacers and bus bars, but were still flexible and "springy".
I'm hoping that the Poron sheet as called for in the e-bike pack build will keep any thing bad from happening.
Going to do a 4S pack build with 26650 cells also. Those cells that I have are rated at 45amp continuous and 60amp pulse. Might have to get four more of those cells to do a 4S2P build as well.

E.Marquez

Where are you sourcing cells?

killer5280

Which cells did you use? The linked site has about a million.
I have an old shrink wrapped JD battery that finally died after 5 years. I wonder if I could use parts of it to make a new battery.

killer5280

This is the link xeris posted in one of the first posts in this thread.
https://liionwholesale.com/

xeris

The batteries available on that site have changed a lot since I first ordered and continue to change every time I go and look at it. There are better choices now than when I ordered my cells.
The Bassen 26650 cells are the ones that I have. The 18650 cells that I used are LGHP6. If I were to order more to make a battery I would consider a Samsung INR 18650–25R

xeris

https://liionwholesale.com/
Based on the reviews at the site it seems like their claim of testing the cells that they get in is real.

E.Marquez

Thanks.. I've been burned a few times now getting old, rehab or fake cells buying from overseas sources...and other times I have gotten quality 123 or other brand name cells. I'm itching to build some new batterys ...but waiting till I have a large enough order to get bulk pricing.