How do I make an alkaline button cell "flatpack"?

For my application I need an 12V A23 battery, but to optimize space I would like to rearrange the tiny little 8xLR932 alkaline cells as shown on the picture. I want to connect them i series, just like an A23. 

The final product is disposable, so I'm thinking of using shrink plastic around the whole thing, but I have no idea which is the fastest and easiest way to connect them. Solder tabs? Wire+glue? Wire+tape? Anything else?

I am also a little worried that all the connections will steal voltage from my battery pack. Will this be a great issue?
Thanks!

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Jack A Lopez9 months ago

I remember one time, years ago, I took apart a flat, disposable, gizmo containing like 30 button cells, all wired in series.

If you can picture it, just from me describing it to you, this gizmo had the same dimensions as a credit card, 54 by 86 mm, except thicker, about 5 or 6 mm thick. The thickness was just, like 1 or 2 mm greater than the thickness of the button cells themselves.

It was intended to be a wallet-sized, personal alarm. One corner of the card was made to break off, and doing this would close a circuit, connecting the series-stack of button cells to an alarm circuit driving a piezo speaker, for to make earsplitting, 90 dB banshee wailing, alarm noise.

The place I bought it from was one of these surplus mongers, like Electronic Goldmine, or BG Micro. They were selling it cheap, essentially selling it for the batteries it contained.

Anyway, regarding the construction of this gizmo, it was essentially molded plastic (maybe ABS?), in two halves, each the same area as a credit card, with little molded walls to hold the button cells.

The tiny metal jumpers, connecting one cell to the next, those were made of something flat, springy, shiny. Guessing the jumpers were made of, maybe nickel plated steel. I think they were also bent and springy, so that they were continuously, if statically, pushing against the button cells.

The two plastic halves that held it all together, I think those were pressed together, and then ultrasonically welded. There weren't any screws holding it together, because it was made to be cheap, and disposable.

I do not think this particular, personal-alarm-card, gizmo exists anywhere in this world anymore. I can't find it via Google Images. But if you want to see similar flat-packed, button cells, sometimes similar battery holders can be found in greeting cards with flashing lights and music. Because, you know, those have to be flat because of rules the Post Office has for how thick a letter can be, and still be classified as a letter.

BTW, I can confirm what Downunder35m says about soldering button cells. It is not do-able because the heat cooks them instantly.

Also, Steveastrouk's idea of using star-washers (small, metal, springy) seems believable, as an option for fabbing this thing in your garage.

Toga_Dan9 months ago

How flat? How lightweight? How resilient? How much current?

Pertinent questions.

Toga_Dan9 months ago

https://www.instructables.com/id/Rechargable-C-Cells-From-Dead-Drill-Battery/. Looking at how mfg do similar stuff can help.

Toga_Dan9 months ago

http://www.ebay.com/itm/like/172202706380?ul_ref=h...

Copper tape. Conductive adhesive? Do they mean electrically? Or heat?

If electrically, I may be in love.

Yonatan249 months ago

There are also flat pack 2032 USB phone chargers that can fit in your wallet.

Toga_Dan9 months ago

http://www.tapesmaster.com/detail.php?pid=4271&cid=1644&gclid=CMX3xYCml9ICFYS1wAodMrANcQ

Copper tape

karolina81 (author) 9 months ago

Thanks everyone, I think I've got what I need now. You have all been very helpful! Cheers.

karolina81 (author) 9 months ago

Hi all and thanks for very good answers!

When googling "cheap greeting card sound module" I find PCB's with tiny batteries everywhere. And for me, that do not even own a soldering gun, this seems like an interesting alternative.

Does anybody know if it's expensive to get a custom PCB design of this sort? I haven't managed to find any standard designs for LR932 yet!

BUT, i also found something similar to what Jack A Lopez described, with the molded pastic thing. However here the metal parts seems to be soldered to lithium batteries, which makes this product a no-go I think.

mold.JPGbatt2.JPG

If you can supply the parts, like the actual cell clips it should be quite cheap to have them produced for you - if the numbers are big enough.
Usually you don't have to bother asking if yu need less than 500 pieces produced.
If you know someone capable of reading and speaking chinese to help you out it should be no problem to order them directly from china for a few bucks.
For example figure out(or let the chinese guy do it) who actually produces the sound modules.
Then contact them and ask for a sample of their battery holders together with your intended final order amount.
If you are lucky and assuming more than 100 pieces you should be able to get a price under 75cents, including the batteries if they are nice.

Not soldered, welded. There are special tools that can spot weld the tabs on for you.

Downunder35m9 months ago

Things that won't work (from experience):
Soldering - bad as these tiny things fail right after.
Aluminium foil - the cell release gas and corrode the foil.
Heat shrink - with a spring in a long pack for sure, not as a flat pack.

The idea with the circuit board is not bad but I would go the simple way:
Cut little squres from the copper clad that are just slightly bigger than your cells.
Clean the copper properly ;)
Place the cells in the center of the clad piece and secure with a bit of hot glue around it.
Use the flat, positive side for this and amrk the clad with a pen for polarity.
Use the other pieces to give the cells a nice "hat".
Now use short rubber bands over the corners and one side to hold it all together.
Solder and place as required.

Spot weld ?

steveastrouk9 months ago

I'd be tempted to make a PCB for top and bottom, then shrink them as you said. Making good connections might mean putting a star-washer on the top and bottom of each cell, or something to just push the oxide out of the way