New Triangle Battery "Box" Design

[LI-ghtcycle]

I posted something on this in the Battery section, but now I want to talk more to the construction of the main battery case holding the battery packs.

I made a cardboard template for all available space inside my newer Trek frame's triangle and used another template of the cross section of a 28v Dewalt battery pack minus the case and BMS.

First off, I was amazed that just removing the battery from it's main plastic case (still keeping the internal black end caps & BMS for now) I reduced it's weight from 2 to 1.5 lbs!!

With my plan to use 16 to 18 parallel 8 cell groups, this is a weight savings of 8 to 9lbs!!. Of course I will be gaining some weight from the battery case and BMS I will be adding, however I believe it will be less than the former pack design I had that required building a mount for each individual battery that included a PCB interface board that had to be soldiered up for each Dewalt pack.

Here are pics of the cardboard template:

And here is a link to the other post showing a lame drawing of the battery case I would be making out of thin (3/32 in.) ABS sheet with tabs to attach to the bottom tube and seat tube:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=19177

The Idea is to have the batteries and TP Packs BMS inside the case with some form of active cooling fans located in the top back corner just underneath the top so that rain wouldn't be dripping into them, and vents all along the case sides that wouldn't let rain drip inside but would allow air flow around the batteries and most importantly the BMS. I might even tuck the controller inside if it's practical, or there isn't room, and it wouldn't hurt the performance, I might have the BMS in a second case on the back rack.

My main concern is that the batter case has to open similar to a "clam shell" and the left side would be fixed, and only the right side would open with either just the flex of the plastic or some kind of hinge at top. The individual battery packs would be secured with a "binder bolt" (the type of fasteners that look like 2 bolts on end with one being the "nut" that the other screws into) holding together the black plastic end-caps inside the Dewalt packs.

These packs would then be secured inside of the form fitting plastic case with 3/4" wide velcro strips so that they could be tightly held in place from all angles. The bottom of the case would again be secured with binder bolts (I suppose they could be T10 just like the Dewalt packs or other tamper resistant fastener) and a charger would be attached as well so you wouldn't have to do anything more than plug it in for charging. My goal is to have a charger capable of charging the entire pack at the same rate as the Dewalt packs charged, so a full charge would take 1 hr or less depending on SOC.

Thoughts?

 

[hurricaniac]

patrickza and I have done this type of ABS box inside the triangle. His thread is at http://endless-sphere.com/forums/viewtopic.php?f=3&t=10256 and there are photos of mine at http://endless-sphere.com/forums/viewtopic.php?f=6&t=235&start=465.

The left side of my box is fixed, but can be rotated out of the triangle and removed easily. The furniture bolts (with T-nuts embedded into the fixed ABS side using a soldering iron) hold it together in a tightly packed, rigid and secure installation.

Here's a diagram of the fixed side with removable cover:

 

[LI-ghtcycle]

Looks good Hurricaniac! 8)

How many AH's of Lipo you got stuffed in there?

My box will be a little wider and require more shaping of the plastic to achieve my desired results, but I'm wanting the same basic result.

There is something about fabric that looks more appealing on a bike however, but I can't think of how I can get the results I want with anything other than plastic! DOH!

I wonder if there is some form of paint-able resin like one would use with fiberglass that could be painted onto a flexible cloth to give it rigidity and waterproofing that I'm looking for.

I am beginning to favor more of a "shrink wrapped" form but rigid and the ability to open it like your box. Even if I go with the ABS I plan to heat it and shape it around the individual packs somehow to make it an even more tight fit. I'm really partial to the look of this design (if it's water proof this might just be the ticket):

 

[Miles]

Have you got a good source for binder bolts LI? I need some 4mm x 25mm..

 

[AussieJester]

I wonder if there is some form of paint-able resin like one would use with fiberglass that could be painted onto a flexible cloth to give it rigidity and waterproofing that I'm looking for.

^^ this is a method used in car stereo industry to make speaker 'enclosures' for cars, fabric is often
strethed over a mdf frame and resin applied to it before bondo and sanding happens.
Same technique could be used for a battery box IMO.

KiM

 

[LI-ghtcycle]

Have you got a good source for binder bolts LI? I need some 4mm x 25mm..

Not a clue yet Miles, but I'll let you know as soon as I do, I just googled "binder bolt" (funny thing most of the time they are tamper resistant and called "SEX BOLTS?!?!" and also weirdly enough used to put together bathroom stalls ... after realizing that I was thinking T.M.I. !! ).

I had only seen them in the garage where my father has assorted bolts and such that he has salvaged over the years.

Here is a site that looks promising, I have no idea about their price or anything else, I was actually going to check the local Fastenal store to see if they sold them.

 

[LI-ghtcycle]

I wonder if there is some form of paint-able resin like one would use with fiberglass that could be painted onto a flexible cloth to give it rigidity and waterproofing that I'm looking for.

^^ this is a method used in car stereo industry to make speaker 'enclosures' for cars, fabric is often
strethed over a mdf frame and resin applied to it before bondo and sanding happens.
Same technique could be used for a battery box IMO.

KiM

Hmmm, very interesting there KiM, I wonder what kind of fabric, and I would want to try something with black stretchy type fabric, use resin and just sand it smooth and avoid adding weight with bondo, but I suppose a good lightweight bondo would work too, the only other Idea I have is to goto a local plastic manufacturer to use an oven and heat each side of the box to the point where it could be laid over the side of the bike in a jig, and then have it conform to the shape of the battery cells with out the black plastic caps inside the dewalt packs, but this would probably be too expensive, complicated and might be too much heat for the battery cells.

I wonder if there is a relatively in-expensive fabric I can get (even better if I can "re-purpose" something cheap from Goodwill) that is already going to help repel water that I can then cut to size, and stretch over my battery packs and use velcro to hold them where I want them and then use the resin to make it solid, and then I could leave the top portion flexible so I could just have a small piece of ABS pipe (1/8 in. cut in half or smaller) to make a tunnel for the break & derailleur cables.

Any Ideas? I'm kinda thinking similar material used to make divers "dry-suits" or if the resin will do the trick, just a strong version of spandex like material.

I had thought of using nylon from an old tent or something before, but that wouldn't stretch.

Part of the idea is to make it look more at home on the bike, not for stealth, just aesthetics.

 

[tritonwow]

Hmmm, very interesting there KiM, I wonder what kind of fabric...
Any Ideas? ....

Looks like the guy uses fleece but any stretchy fabric (wetsuit neoprene may work but may be too heavy when it's done) which the resin doesn't dissolve should work for your base layer.
http://www.explorerforum.com/fiberglass/fiberglassing.htm

You'll have to build a base layer of of non-penatrable plastic (I use the stuff they use for a vacumn bagging) so the resin doesn't get all over your bike/parts (or stick to them). A mold release may also be necessary (carnuba wax is one type) Also, the resin gets hot while curing so it's a consideration. Then you'll need to put on fiberglass to strengthen it.
After a few layers you can remove it and continue to build off the bike.

Triton

 

[LI-ghtcycle]

I weighed my bike today even with-out the old battery pack and I was shocked to realize it's 56lbs!

It seems I may have miscalculated previous estimates!

So maybe I need to re-think the idea of a rigid case and go more light-weight. My intent has always to make the battery case integral to attaching it to the bike, instead of separate containers to hold cells that are then held together by an outer case.

Maybe I will have to first attach the batteries and then cover them much like adrian's, minus the duct tape.

Maybe I should just admit that I'm hooked and I want MORE POWER!!

I'm going to have to start looking into one of those metal geared oil bath geared motors!

 

[LI-ghtcycle]

I went looking at some different fabrics that might work for the battery cover, and I'm thinking Neoprene might fit the bill, should repel water and stretches a little and then feels pretty strong, I might have to go with a more permanent and less accessible pack build, and just have the cells held together in a group with shrink-wrap in the shape of the triangle, this will be cleaner and less blocky anyway.

I was also thinking about cushioning the battery, and saw where some RC plane hobbyists would use closed cell foam rubber to protect their batteries in crashes. I'm hoping the 1/8th in. thick neoprene will help in this regard too.

Maybe I can use thin copper buss material to solder the bent-back tabs onto in the groups of 8 and then just shrink-wrap the whole thing together.

I have seen some custom made packs with shrink that are triangular shaped, but I'm not sure where to get wrap that large? Or if it comes in a triangular shape to begin with?

 

[moostrodamus]

All i have is a skill saw, but i am working on a box for the triangle. My hope is once i get it all together with all the nessasary holes and mounts I will price getting the box made with aluminum...thats what i am thinking anyway. For now making do with the tools (tool) I have on hand.

Moo...

 

[LI-ghtcycle]

Looks good Moos!

I have thought about getting some aluminum sheet myself, but I just don't like the look, I really want to find some kind of material that is made of 6 plys of thin Neoprene or something so that it's really strong while still stretchy.

Gonna call up a mill-end store today and get some more info on what they have.

 

[LI-ghtcycle]

Ok, I took the plunge!

I found a local mill-end store and bought some thick Neoprene designed for diving suits, and I am really impressed!

I think this stuff is going to more than fill my requirements for strength and protection. I believe it's 4 mm thick, and it stretches like a big sheet of elastic, and it's basicly closed cell foam rubber so I believe it should offer plenty of impact protection especially since it will move if struck. I understand it has some abrasion resistance properties too, but I thought I might look into adding "sliders" like you see on sport bikes, the little plastic nubs that stick out a little further than the sides of a sport bike to protect the plastic if it goes down.

I'll post some pics soon.

 

[hurricaniac]

Looks good Hurricaniac! 8)

How many AH's of Lipo you got stuffed in there?

I'm using 6s 5000mah Turnigy's for a grand total of 44.8v and 15ah. I'm considering using Doc's parallel-series set of Kilovac relays to have on-the-fly switching to go to 66v and 10ah. The need for speed is a disease...
-Bruce

 

[moostrodamus]

Hi LI-ghtcycle,

I'm not familiar with the term "Mill End Store" Is its a place to buy leftovers of material from manufacturers? Id be real interested to know to see if i could find something like that here in Toronto or Canada. Any suggestions for a search on the internet? Love to get my hands on so leftover aluminum sheets. Only place i could find only sold 4X8 sheets at CD$ 150...

Thanks,
Moo

 

[Chillboy]

For fiberglassing over cloth I've always just used old t-shirts.
But I only buy the cloth and matt and use a super-hard 1:1 marine expoxy for resign.
Get a roll of shrink wrap for wrapping skids and do the whole area on the bike you want to glass.
Stretch the tshirts over and secure them.
Cut all the pieces and lay them out dry and have them ready to glass.
Then it gets stinky

 

[Chillboy]

If you want some flex to the design, or shapely inside to your box check out UV fiberglass.
Spread it out in the shade then drag it into the sun to cure.
Just like reg. fiberglass it has a sweet spot in it's curing time to sand then sets up really hard but remains flexible.
It might be smart to use this on the inside and wrap the battery in plastic and press it into it for support on the inside with
the outside sanded nice and smooth and painted.
I know you guys don't like gas tanks *jk but this was the best way to get mine where I wanted it on this seaflee.

This flat project started with a tshirt, 2 layers of cloth and 2 layers of matt then I used the UV fiberglass (paint can).

 

[LI-ghtcycle]

Very cool, thanks for the info CB!

I like the idea of it being flexible after it's set. How expensive is the resin?

 

[Chillboy]

They do make UV fiberglass but sorry I meant to say bondo is what I used on top of the reg. fiberglass.
iirc a can this size was about $20. I got it at Canadian Tire, it shouldn't be too hard to find elsewhere.
http://www.jamestowndistributors.com/userportal/show_product.do?pid=6094&familyName=Bondo+UV+Sun+Activated+Body+Filler

 

[LI-ghtcycle]

Kewl, I like the flexibility! The last time I used Bondo was like 10-15 years ago, and it wasn't anywhere near that flexible, right now I am trying with a Neoprene Cloth with out anything else on it, I plan on stretching it just enough so it's under tension, but can still flex safely with out risk of tearing (that's the hope anyway) just waiting on a few more supplies and fixing my lights for now.