Circle Pack of 18650s design hopes led to Wolfram Alpha

[tnttburbank]

I'm planning to build a circular shaped pack and I searched for designs and had trouble finding any. However Wolfram Alpha has an interesting tool that lets you specify layouts:
(sigh newbie you'll need to make link)wwwwolframalphacom/input/?i=pack+circles+of+radius+18mm+in+a+circle+of+radius+145mm







Very interesting results.

You can even specify packing in a square:
(sigh newbieyou'll need to make link)wwwwolframalphacom/input/?i=pack+circles+of+radius+9mm+in+a+square+of+side+220mm





Might be useful to optimize layouts and use the images to draw the parallel pack connections.

Cheers,

Tom

 

[Korishan]

Interesting.

Why would you want a round pack? I can't think of an application atm for a need for it.

 

[DarkRaven]

Why would you want a round pack? I can't think of an application atm for a need for it.

For your selfmade, high power LED flashlight built into a piece of PVC pipe, obviously!

 

[zag2me]

Because they look very cool, good enough reason for me

 

[Mazlem]

Because you want your trashcan Mac to be useful again.

 

[tnttburbank]

Interesting.

Why would you want a round pack? I can't think of an application atm for a need for it.

I have a 120V tower fan that has a circular base and I plan to make a 2 levelcircular base with casters on the bottom level and have the tower fan be "wireless" from anywhere in the room. Since the base was circular it got me wondering how to calculate the maximum number of cells that could fit in the space. Got me thinking of PowerColumn instead of PowerWall. I just got into this and I have to test my first 100 used cells so it will be a while until the unit gets built. I want to start with a smaller pack first to try out the various techniques.

 

[ozz93666]

You've read my mind , tnt ... that's what I'm building , but perfect hexagons ... the sides need to be odd numbers to get a perfect and optimum spot welding of the nickel strip ....

A hexagon of 7 cells on each side has a total of 127 ....makes up one 127p brick .... 5 cells on each side gives 61 .... a 61p brick , you have to decide the brick size that best suits you , and only use that size ...can even use 3 cells on each side makes a 19p brick

I put a new sleeve on each cell , spot weld nickel strip on top and bottom connecting cells firmly together , a touch of super glue where the cell's sleeves touch and it's as solid as a brick!!!(no fuses of course)

But get this .... no need for connecting wires ,you just stack them on top of each other to make a "POWER TOWER" as tall as you like...

I know what you're all thinking .... how can you get a secure and reliable low resistance connection when each p brick is just resting on top of the one below??? ....

If constructed well the nickel strip makes a very flat surface and has contact at 100 different points to the bricks below and above , they are heavy and push together making a firm contact .... the ultimate in serviceability since you can disassemble the tower easily ...

The bottom brick of the tower rests on an aluminum plate ... that's one terminal of the stack to which a wire is connected ... likewise the top brick ....

The current path could not be shorter hence very low resistance.

For a visual indication of voltage of each brick cut open a junk cell and put a small voltmeter inside , then put the sleeve over the cell and heat shrink ...the voltmeter can be seen shining through the plastic sleeve, put one voltmeter cell in one corner of each brick .... for those who prefer balancing , just slip the wire between each brick.

 

[completelycharged]

Stacking packs is ok if you don't plan on fusing individual cells. The other issue is heat transfer because cells in the core will get very hot so the design may need selective missing cells to form additional airways for cooling if there is no forced airflow through the smaller gaps..

A round pipe makes for the option of having a long series pack, boring a hole in the ground and putting the pipe in. Fully waterproofed, ground cooled... One 2.2m x 110mm diameter underground waste pipe can contain over 5kWh of cells. 32s22p (120V).

 

[Korishan]

The other issue is heat transfer because cells in the core will get very hot so the design may need selective missing cells to form additional airways for cooling if there is no forced airflow through the smaller gaps..

This would be perfect for those "blank cells" that some packs have.