What is best orientation for a prismatic cell battery pack?

[Russell]

Assuming you can orient your soft cell lithium battery pack in any direction what would be the best to protect it from road shock?

Standing upright?





Resting on its side?





Or lying flat like pancakes?




Anybody know for sure?

-R

 

[dogman dan]

No Idea, but since nobody has said anything, I mounted mine on its side, 2000 miles ago. I can see how flat like pancakes could be a problem if they need to expand some, but I doubt it matters between upright and on the side. Box it up somehow though, so you don't tear up corners when the bike falls over.

 

[Russell]

I don't own a lithium battery…yet. The pictures are an example where the individual cells can be seen to illustrate my question. My own guess would be "on their side" would be best but I have no info to back that up. Since there are many Ping batteries floating around which use the soft cells I thought someone might know if say laying the battery in the "pancake" configuration was harmful or not.

-R

 

[Aerowhatt]

Upright is best. The guts of the battery are basically hanging inside the pouch so having both tabs having equal tension stress makes some common sense. It's how the batteries are tested in most cases!

Flat is worst, the bottom cells have the weight above crushing them. If they were made to support weight they would have a hard case.

On it's side would be second best, but upright is ideal. Any placement should include a nice straight stiff base for the battery and a modest amount of resilient foam to help reduce the hard edges (Highest G's) of the shocks.

Aerowhatt

 

[GCinDC]

Newbie here... In love with my first kit...

Ping built me a long skinny pack (13" x 6" x 3") to fit in the frame's triangle (11/08). I've been looking for the perfect case for it ever since, from power tool cases to toiletry kits to laptop bags. (I'm going mad...)

In the meantime, I've had it wrapped in a lightly padded nylon bag (dollar store) and hanging from the crossbar by two straps, and anchored at the bottom corners by velcro straps.

After 200 miles, I recently unpacked it to stow it into a bag I designed and sewed for the purpose (madness).

Anyway, I found slight indents at bottom around the straps and a slight sag in the middle. With delusions of reconfiguring the cells, I peeled back some tape at the corner to peek. At top and bottom of the pack, there's what looks like a thin grey piece cardboard strip. I was relieved to see it but am sure it can't provide much support. I'd like to get the pack in a hard shell, so now I'm exploring how to make a case with PVC Sheet...

If anyone has suggestions, please advise. In the meantime, I'm just going to start sharing my story...

 

[monster]

you could buy some plexiglass from a hardware store and heat bend it. make a hot wire rig to heat bend long edges accurately.

or

you could get some sheet metal and duct-tape to insulate it.

 

[docnjoj]

Dont forget plywood for easy working!
otherdoc

 

[pakobike]

Clearly the box depends on the shape and extent of the battery pack, but looking aluminum boxes found this CD.
To suit the different parties clearing the cut and went back to riding.
Maybe a briefcase that approximates the measure and can be amended to place your battery.
Cells of the battery work in horizontal, below there is a layer of foam.

I hope this is understood, my English is very basic

Saludos

 

[dnmun]

why not use a plastic milk jug and cut off the top and one side and set you pack inside it with some open cell foam to support the weight. it looks like your pack is about the right width, use 2 jugs with the cut open ends facing each other and surrounding the pack, then tape it up some more, very light and capable of preventing penetration by most possible dangers. with the upper part open, you can get to the top later also. i think vertical is best, to allow the separators to hang from their top, and the vent is in the top too, i think.

 

[GCinDC]

Russell, Sorry if I hijacked your thread! Thanks, everybody, for the suggestions.

I went to the hardware store (twice), all revved up to buy a 2x4' sheet of optix arcylic to play with but was misquoted at first -- it was going to cost $70...

I'm stubbornly evaluating my requirements:

__ structurally solid, can handle some curb jumping
__ lockable (urban; i never used to worry about locking my old bike, and now i'm afraid to leave it anywhere!)
__ firmly mounted and weatherproof electronics: switch, charge & discharge connectors
__ moderately easy to remove battery (dream on, right?)
__ enclosure for controller too? (not sure about this)
__ hard shell to support/protect battery
__ low CG
__ small box or place for emergency junk (fuse, parktool, tape, velcro ties)
__ leaves enough room to grab and lift bike at the cross bar (near the seat -- the sucker's heavy now...)
__ not attention getting... lol

pakobike, do your legs hit the case? Believe me, I've been looking ALL OVER for cases like that. I've been eyeing the propane torch case in the garage... Do you open yours to charge it? Where'd you get the lights?

 

[Pure]

Why not use carbon fiber to make your own box. I've been dying to find an excuse to play with it. It's a tad expensive but would be very light and would def do the job. Just design your box then carve a life size replica of what you want it to look like out of styro foam. Stack and glue sheets of it together until you get a piece the right size. Then wrap the box in a garbage bag and use duct tape to smooth down the excess bag. Then apply your carbon fiber. After it dries, use a rotary cutting tool to cut it in half to remove the styro block. Install your battery then put it back together. To reattach the two sides just run a strip of aluminum over the seam. Don't forget to seal the seam with silicone. Heck if you didn't care about getting the battery out very easily you could just reseal the seam with another strip of carbon fiber.

I have no clue if my method would work but as you can guess I've put some thought into it. If anyone knows of a better way to work with it please tell me.

You can find all kinds of suppliers on the net. Just google "carbon fiber cloth" Here is the first example I looked at. http://www.jamestowndistributors.com/userportal/show_product.do?pid=2782&familyName=Carbon+Fiber+2x2+Twill+Weave

 

[Drunkskunk]

Orintation doesn't matter.

I run these pouch cells in RC planes, and have cracked the carbonfiber wingspar (that could suport my body weight) in a tight turn at 100mph+, for a 16 ounce plane, that was 150 to 200 G's. The plane took loads of over 50 G's often, and I've never had trouble with these pouch cells being crushed or being vibrated to death.

A good box to keep them from being bounced around is helpfull, but you can mount them upside down, and strapped to the spokes if you want.

 

[GCinDC]

Carbon Fiber sounds amazing! I only wonder about the strength where I'd mount it to the frame. I'll need to research this to understand exactly how it could work. I love the idea, and thanks for the link.

 

[Russell]

Upright is best. The guts of the battery are basically hanging inside the pouch so having both tabs having equal tension stress makes some common sense. It's how the batteries are tested in most cases!

Flat is worst, the bottom cells have the weight above crushing them. If they were made to support weight they would have a hard case.

On it's side would be second best, but upright is ideal. Any placement should include a nice straight stiff base for the battery and a modest amount of resilient foam to help reduce the hard edges (Highest G's) of the shocks.

Aerowhatt

Orintation doesn't matter.

I run these pouch cells in RC planes, and have cracked the carbonfiber wingspar (that could suport my body weight) in a tight turn at 100mph+, for a 16 ounce plane, that was 150 to 200 G's. The plane took loads of over 50 G's often, and I've never had trouble with these pouch cells being crushed or being vibrated to death.

A good box to keep them from being bounced around is helpfull, but you can mount them upside down, and strapped to the spokes if you want.

Of course what you can do with a few cells properly restrained in an aircraft is a bit different than what should be done with a 60 cell Ping pack, of that I think we can all agree :| Since the limitation for me will be the dimensions of my two rear trunk bags I will probably be lying the cells on their side.



-R

 

[GCinDC]

Pure,

I checked out your link, and am intrigued by the process. The video shows application of several sheets on flat table surface... Fairly simple compared to:

Then wrap the box in a garbage bag and use duct tape to smooth down the excess bag. Then apply your carbon fiber. After it dries, use a rotary cutting tool to cut it in half to remove the styro block

My questions are:

- How many strips of the cloth to use? Say, to make a thickness of 1/8"? Or would 1/16" width be enough?
- What all would you buy to make a triangular box measuring 20" (at crossbar) x 17" (downtube) x 24" (bottle bracket tube)?
- Could I integrate an internal aluminum shelf, by making the foam shape, then slipping an aluminum bar through and then applying carbon fiber cloth around it..?

Any thoughts? Or links to threads where others have done it?

Thanks,

Greg

 

[Aerowhatt]

Orintation doesn't matter.

I run these pouch cells in RC planes, and have cracked the carbonfiber wingspar (that could suport my body weight) in a tight turn at 100mph+, for a 16 ounce plane, that was 150 to 200 G's. The plane took loads of over 50 G's often, and I've never had trouble with these pouch cells being crushed or being vibrated to death.

A good box to keep them from being bounced around is helpfull, but you can mount them upside down, and strapped to the spokes if you want.

Apples and oranges my friend. I fly high performance RC planes too. With a 16 oz plane you are talking about a 3 or 4 cell battery weighing less than 5 oz. A far cry from 15 20ah cells all resting flat on the 16th one!

Vibration in a high performance RC plane?? My props turn between 10,000 and 22,000 rpms. Everything has to be perfectly balanced or it comes apart! Compared to a hardtail bike on the average city street the RC battery sees no vibration what so ever.

Encouraging people to abuse batteries which contain significant amounts of energy is dangerous and irresponsible!

Aerowhatt

 

[JinbaIttai]

I might be way off on the physics, but it seems to me that a 65lb bike cartwheeling to the pavement at 25mph has more energy to get rid of than a 1lb plane doing 100 mph.

 

[Drunkskunk]

Orintation doesn't matter.

I run these pouch cells in RC planes, and have cracked the carbonfiber wingspar (that could suport my body weight) in a tight turn at 100mph+, for a 16 ounce plane, that was 150 to 200 G's. The plane took loads of over 50 G's often, and I've never had trouble with these pouch cells being crushed or being vibrated to death.

A good box to keep them from being bounced around is helpfull, but you can mount them upside down, and strapped to the spokes if you want.

Apples and oranges my friend. I fly high performance RC planes too. With a 16 oz plane you are talking about a 3 or 4 cell battery weighing less than 5 oz. A far cry from 15 20ah cells all resting flat on the 16th one!

Vibration in a high performance RC plane?? My props turn between 10,000 and 22,000 rpms. Everything has to be perfectly balanced or it comes apart! Compared to a hardtail bike on the average city street the RC battery sees no vibration what so ever.

Encouraging people to abuse batteries which contain significant amounts of energy is dangerous and irresponsible!

Aerowhatt

6 ounce 3 cell with dimensions of 4.6"X1.7" would have a total weight of 37 pounds pressing on the top of the bottom cell at 200G. thats 4.75 pounds per square inch.

A 16 cell pack can have various sizes and weights, but lets say its a heavy 20 pounds, and 4X9 inch cells would have a total weight of 18.75 pounds pressing on top of the bottom cell, or 1.92 pounds per square inch.

Ultimatly, it matters what the manufacturer says. If they haven't said Don't stack them horizontaly, there's no reason to think we can't without some other evidance of trouble.

And who's encuraging itrresponsable behaviour?

 

[Russell]

Take a look at this post;

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=8174&st=0&sk=t&sd=a&hilit=ping+bad#p124210

I think there's only ONE WAY to position THAT battery and it's right side up

-R

 

[JinbaIttai]

Take a look at this post;

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=8174&st=0&sk=t&sd=a&hilit=ping+bad#p124210

I think there's only ONE WAY to position THAT battery and it's right side up

-R

Photo taken the day the swelling was discovered.

 

[JinbaIttai]

Here's how it used to look.

 

[Pure]

Pure,

I checked out your link, and am intrigued by the process. The video shows application of several sheets on flat table surface... Fairly simple compared to:

Then wrap the box in a garbage bag and use duct tape to smooth down the excess bag. Then apply your carbon fiber. After it dries, use a rotary cutting tool to cut it in half to remove the styro block

My questions are:

- How many strips of the cloth to use? Say, to make a thickness of 1/8"? Or would 1/16" width be enough?
- What all would you buy to make a triangular box measuring 20" (at crossbar) x 17" (downtube) x 24" (bottle bracket tube)?
- Could I integrate an internal aluminum shelf, by making the foam shape, then slipping an aluminum bar through and then applying carbon fiber cloth around it..?

Any thoughts? Or links to threads where others have done it?

Thanks,

Greg

What you are seeing in the video is just an example of how to lay it. You have to have some sort of structure to provide the shape until it dries. The bag keeps the resin off of the styro. Resin will melt it so you can't let the 2 touch. And if you can't get the bag off, no big deal as it's added weight would be negligible.

The problem with carbon fiber is the expense. To be able to make the box thick enough to support the weight of the battery would put a real hurting on your wallet. Then there is the problem with it's rigidity. The constant weight of the pack combined with the vibrations from the bike would surly crack it. Probably at the point of stress with the most weight on it. So...

The most economical way to use it would be to think of the box you are making as a strong, light, water proof shell. Build your actually battery hanging system out of something like this. http://www.ronshomeandhardware.com/ProductDetails.asp?ProductCode=609586&click=1014 . Google aluminum angle stock. Shop around as I know you can find it cheaper. That was again just the first link I looked at on google.

I've built many a RC car chassis out of smaller stuff than this and I can tell you it is strong! I wouldn't use anything less than 2 inch stock for our batteries. What you would do would be to make a battery cage and mounts using this. If you cut it right it can be pieced together with small flat top screws and lock nuts. (the Little nuts with plastic on the threads) Then design your box out of carbon fiber to envelope this. Use a flat 2 inch stock bent to fit around the battery for extra support. Wrapping the battery frame in duct tape wouldn't be a bad idea. Just make sure you leave enough space in your measurements to accommodate it. You want it tight, but you still have to get the battery in it before bolting up the bottom of the frame.

All of this might be a bit hard to do with your space limitations. Ideally I'm more or less thinking of a saddle bag type setup. I want my batteries as low to the ground as possible.

As for the thickness of the carbon. If you went with a total carbon fiber with aluminum supports (yes you can put it in like that) your carbon would need to be pretty thick. Probably at least 4 sheets of that stuff I'm linking below. That was the thickest of the 3 types I saw they had. It would have to have extra carbon layers around any type up aluminum running through it like your thinking.

For what I want to do, simply wrapping the styro in this http://www.jamestowndistributors.com/userportal/show_product.do?pid=1443&familyName=Carbon+Fiber+Tape first then putting a covering layer of this http://www.jamestowndistributors.com/userportal/show_product.do?pid=6158&familyName=Carbon+Fiber+Cloth+Plain+Weave+12K should be strong enough. If you wreck your bike it will crack but that is probably going to happen no matter how strong you make it.

Make sure you insert aluminum tabs in between the layers every where you would want to drill it.

As stupid as it sounds I got my idea for using styro as a form from Mythbusters.

 

[Drunkskunk]

Expanding on what Pure said, and since I've done some foam loss building as well, all carbonfiber would get expensive. a thin layer of it would be strong enough, but not ridged enough. Fiberglass, on the other hand, is cheap. you can actualy build a composit of several layers of fiberglass encased in a layer of Carbonfiber and get the benifits of rigidity and striength.