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18650 pack build using plastic battery holders

Posted: Aug 23 2015 11:21am
by www.recumbents.com
An easy to build battery pack
There has been an explosion of choices in new high power batteries for the intrepid e-biker, but the best option as of this writing are the 18650 form factor Lithium ion batteries using the NMC formulation. These batteries are called INR or NMC and are of Lithium manganese nickel formulation. This chemistry combines the safety of LiFePo4 batteries and the high energy and density of LiPo. A disadvantage is that they do not have the longevity of some other formulations. After 250 cycles these cells will be down to about 60% capacity. Is this really a problem? Not for me, it will take me several years of fair weather commuting in the Midwest to get to that many cycles and by then a new, better, cheaper batter will be available.

The biggest issue with building e-bike battery packs out of a bunch of small batteries is how to connect them together. They can be soldered together but the heat of soldering may damage the battery. They can be spot-welded but that requires specialized equipment that is not available to the average home builder. In addition, many battery pack builders just heat shrink the batteries together which leaves them vulnerable to damages from dropping or crashes. Initially I thought that building a battery pack in a Hammond aluminum box would be a good idea, but I ran into issues and abandoned the build.

I am now working on a build using plastic battery holders, Click this link to skip to the start of the 18650 battery holder build

or your can read through the sordid tale of the abandoned build that came before it...

Some of the comments below may not make sense because I changed this first post (sorry!).

-Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 23 2015 12:41pm
by spinningmagnets
Great idea, and the drawings are we done. What program did you use to make the drawing?

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 23 2015 1:22pm
by www.recumbents.com
Hi Ron,

I use paint shop pro v7. An oldy but goody. Corel still makes a version of the app.

If this ends up working well I'll supply 1X PDF drawings so people can just print out the layout at 1X on their inkjet printer, glue the paper to the sheet of conductor, mark the battery centers for dimpling, and cut out the patterns. That should simplify things somewhat.

Or I could just buy a http://lunacycle.com battery and save myself the hassle. :mrgreen:

-Warren.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 23 2015 3:59pm
by kenkad
Warren,
Thought I might spend a couple of hours on the 3D CAD because I have a good deal of interest in these type of battery assemblies. Thank you for your post.

I took your idea and extended it a bit. First, I did not see a whole lot of gain by staggering the batteries, so, I put them in line. The idea is that someone may have a polyethylene extrusion that provides (say a 6 cell wide strip) the 'crate' for the cells. In addition, it allows a better uniform copper 'strapping' senario, three different patterns for whatever series configuration. I did a 4P to show in the following JPGs. Enjoy them and copy to your hearts content whomever is interested. Much better than spot welding. You could easily add small tabs for the BMS leads, etc.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 24 2015 4:01pm
by www.recumbents.com
Nice KenKad, does it still fit in the chassis arranged like that?

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 24 2015 7:14pm
by Hillhater
I think Kenkad missed the point about using the off the shelf metal box for a 48 cell pack .!
kenkad wrote:. First, I did not see a whole lot of gain by staggering the batteries, so, I put them in line.
.. try getting 50 cells in that box without staggering them !

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 26 2015 8:31am
by marty
Aluminum box I like. Plastic battery enclosure is good. Fabric bag is asinine, extremely stupid and foolish.

This was MY idea.
From 2007
https://endless-sphere.com/forums/viewt ... +companies

Re: Duct Tape E-Bay Lifepo4s???

Postby marty ยป Mon Jan 28, 2008 9:13 am
Put batteries in a plastic box.
Here is a list of plastic box enclosure companies.
http://www.budind.com
http://www.hammondmfg.com
http://www.hoffmanonline.com
http://www.altechcorp.com
http://www.boxenclosures.com
http://www.daviesmolding.com
http://www.okwenclosures.com
http://www.pactecenclosures.com
http://www.polycase.com
http://www.pomonaelectronics.com
http://www.serpac.com
http://www.tekoenclosures.com

Some of these links from 2008 might be broke?

Good places to search for a specific size
http://www.newark.com/
http://www.mouser.com/
http://www.alliedelec.com/

Might be able to search by interior dimensions? Haven't looked into this recently.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 28 2015 1:22pm
by www.recumbents.com
I just purchased the following from Amazon:

Enclosures, Boxes, & Cases 7.38X4.7X3.07 - $25.03 + $8 shipping
https://www.amazon.com/gp/product/B005T8QLN8
18 Gauge Copper Sheet - 6" x 12" - $21.85
http://www.amazon.com/gp/product/B00YT3TP2S
Silicone Wire - Fine Strand - 10 Gauge - 10 ft. Black, 10 ft. Red - $19.99
http://www.amazon.com/gp/product/B00BWYMBO6
Dimple Pliers - 7mm (Blue) - PLR-726.70 - $22.95
http://www.amazon.com/gp/product/B008SGDV7C

And I also ordered 50 Samsung 25R batteries from lunacycle.com - $202 with shipping.

Total - $300



-Warren.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 30 2015 2:41am
by markz
Great idea, I have been spending the past hour or so looking at off the shelf enclosures myself.
At first I was randomly searching mouser.com for some ideas, then it hit me, electrical boxes. So I go to B&E Electronics (Because thats my new go-to store for anything electronic/electrical) and have found several options that look quite appealing to me. ABS, alum, steel, styrene boxes all of various different sizes. I found boxes that can hold 50+ 26650 batteries non staggered for $12+. I just round the diameter to 1 inch and length to 2.6"

You can add Hammond Instrument Case to your list of companies. I will just post what I am looking through and there are many companies selling boxes.
http://www.be-electronics.com/SearchRes ... =50&page=4

This approach looks promising to me, as I can go several different ways with how I want to build my battery box. I can have modules that slip into the old lead acid case, or buy slightly larger boxes to fill the space in my bike frame, and epoxy the boxes together to suit my width, length and height needs.

I've been racking my brain all day trying to find a suitable means for a box, even tempted to just find some pipe. I still think I should wait until my 26650 holders come in from SlowTech (Fast Tech)

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 30 2015 2:50am
by cwah
The box is almost 600g... which is for 50 cells at 2.5kg about a quarter of the total weight!

It adds significant weight to the system!

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Aug 30 2015 12:46pm
by markz
Yeah weight is a concern, me now my bike is so heavy I dont care anymore.

This is a ABS box, most likely light. But has the screw holes/mount impeding box space.
http://www.be-electronics.com/product_p/rl6685.htm

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 01 2015 11:44am
by www.recumbents.com
The parts are starting to arrive.

I now see that the 18 gauge copper sheet is a bit on the thick side (.0478 inches) so I'm going to order some thinner copper sheet. Probably the .021 thickness is plenty thick. The thicker copper may see "bus bar" duty...
Ordered 26 gauge (.0217 inches) copper sheet: http://www.amazon.com/Solid-Copper-Shee ... B00QXZ0TK2

The 10 gauge silicon insulator wire looks good.

-Warren.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 04 2015 7:19pm
by www.recumbents.com
The batteries arrived and though they were rattling around in the box they appear undamaged.

Here's what the batteries look like in the case:

Image

As calculated there is still space for wires, a fuse, and connectors in the case.

Next step is to make the 1x printout of the cell interconnects and cut out the copper shapes.

-Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 06 2015 2:04pm
by bgt
BMS????????

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 06 2015 3:39pm
by www.recumbents.com
No BMS. I will bulk charge and balance with my balance charger when needed. LVC cutoff is handled by the CC HV160 controller. This worked fine for my LIPo pack, should work for this one as well.

Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 11 2015 11:45am
by www.recumbents.com
I got the drawings printed out to scale and create a PDF of the drawings which should allow anyone to print them out to scale as well (updated first post with a link to the PDF).

Next steps:
* use spray adhesive to glue the paper patterns to the copper sheet
* cut the patterns out of the copper
* use dimple pliers to make dimples

-Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 13 2015 12:09pm
by www.recumbents.com
I used spray adhesive to fasten the 1X printout to the 6" x 12" copper sheet. Here you can see the conductors ready to be cut out. I drew in tabs for the main power wires and the balancing wires. Also I added numbers and arrows to make it easier to figure out where the conductors go after they are all cut out.

Image

To cut the conductors out I used my old trusty aviations snips. I did have to to some filing and flattening afterward to clean up any jagged edges and ensure they were flat. Cutting out the conductors took several hours.

Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 13 2015 2:57pm
by markz
Are you going to tab weld them or whats your connection going to be?

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 13 2015 6:24pm
by www.recumbents.com
Markz- I am going to use foam and the pressure of the screw-on lid to provide enough pressure to make a good connection.

After the cutting and cleanup it was time to add the dimples. the + and - symbols are sort of in the right place but I measured and drew lines on the paper that was still glued to the conductors after they were cut out to make placement of the dimples more accurate. After that, using the dimple pliers to make the dimples was easy. I'll update the PDF with marks for the actual dimple centers later...

Image

Next, I wetted out 3 layers of fiberglass with West Systems epoxy and left it to cure. I embedded another copy of the layout between the layers of fiberglass to make it easy to see where to glue the copper conductors down...

Hey, do you guys think if I tin the dimples with some silver-tin solder that they will be more resistant to corrosion than the bare copper?

-Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 14 2015 9:48pm
by www.recumbents.com
The fiberglass top and bottom substrates for the conductors turned out well. I tried to tin the dimples with silver solder but I don't think my iron is hot enough. Maybe I will try the torch :)

Image

Next steps will be to solder the balance wires to the tabs and glue the conductors down to the top and bottom substrates.

-Warren

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 14 2015 11:07pm
by markz
Good point, I've been thinking about pressure like that as well. Your way seems logical.

Dimple Pliers, how much? and where did you buy them?
What size did you get? Is it the right size?

I'm trying to buy local now, so what kind of store, Home Depot, Rona, Lowes, Home Hardware? or is it more of a crafty type hobby store?

Thanks

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 15 2015 5:40am
by Punx0r
Excellent work :)

a small dab of anti-corrosive grease for electrical connections should protect the contact points from corrosion. However, silver solder will probably also works well, you just need a nice, thin, flat even coating. I would try heating the piece in an oven to get a nice, even heat that will let the solder flow properly.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 15 2015 11:51am
by www.recumbents.com
Markz- Dimple Pliers - 7mm (Blue) - PLR-726.70 - $22.95 http://www.amazon.com/gp/product/B008SGDV7C

Punx0r - Thanks! My chances of getting a consistently even layer of solder are pretty slim. Time to order the grease.

-Warren.

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 15 2015 4:58pm
by spinningmagnets
4P of the 25R cell is 10-Ah, and at 20A per cell, that's 80A from this very small pack.

I recently wrote about new cells that have 3500-mAh and are capable of 10A per cell...using those, this case would be an incredible 14-Ah with a 40A capability...pretty sweet for such a tiny box

The GA, MJ1, 35E, and the Tesla-B...

Re: How to build a 18650 pack in an off-the-shelf metal box

Posted: Sep 15 2015 11:15pm
by Hillhater
spinningmagnets wrote:4P of the 25R cell is 10-Ah, and at 20A per cell, that's 80A from this very small pack.

I recently wrote about new cells that have 3500-mAh and are capable of 10A per cell...using those, this case would be an incredible 14-Ah with a 40A capability...pretty sweet for such a tiny box....
Yes , attractive figures,...but remember the voltage sag you are going to get at those levels,...much more than an equivalent capacity Multistar lipo pack.
You are probably going to be giving away 3-5 volts on a 12 S pack.