Hi Everyone,

I'm looking for ideas on how to power a circuit I want to put into my wallet. The trick is that I want to keep the wallet as thin, thin, thin as possible. The circuit runs (typically) off a single 3v coin battery.

Standard coin batteries would be just fine to use. Appealing for cost reasons too. But they require an interface. some way to connect them to a couple wires. if a couple batteries could be stacked side by side to increase circuit lifetime, that would be even better.

All the coin battery holders ive seen are pretty thick. designed for PCB mounting. Far too thick to fit into a credit card slot. There must be other options out there too.

rechargeable would be GREAT too, but I don't mind changing batteries. If it came down to a half millimeter of thickness versus rechargability, I'd take the thinner solution.

What's out there?

 

As to connecting to coin cells, that should be easy. Any thin clip, such as a money clip, with connections will do it. There are also clothes line clips, alligator clips, you get the idea. You will need insulators, but carpet tape is extremely strong, and is fiber glass based, so it should work.

For high capacitor cells, there are always cell phone batteries.

 

Another thought, it doesn't have to be coins, but thin strips of metal with wires attached all tightly taped together.

 

Check out musical birthday cards and hack that battery holder.

John

 

You can buy coin cells with PC tab welded to them.
Here is a link:
http://www.mouser.com/catalog/catalogUSD/640/2075.pdf

There are some electronic distrbutors that have value-added departments that can spot weld tabs also.

 

Yep, get the coin cells with the spot-welded tabs.
Don't try to solder wires/tabs on to coin cells - they WILL explode!

 

You might want to contact the technical representatives of some battery companies, for two reasons. One, they'll know if there are some specialty batteries that are available that the hoi polloi may not be familiar with.

Two, it's possible that you may be misapplying a coin cell, considering that there may be mechanical pressure and stresses on it different than when it is held in a holder. You don't want to be like those kids in the 60's who walked around with Zippo lighters in their pockets because they thought they were cool. When they were filled with naphtha, the vapors would leave a nice, annoying red rash on your skin. I can imagine that the chemicals in a coin cell might be worse to have in skin proximity...

 

Remember the Polaroid instant-developing photographic cartridges that hold the pack of pictures-to-be ?

That may be what you are after. There is a wallet-size, cardboard thin battery in them as I remember, and they last way longer than you can imagine.

You may still get the film packs somewhere.
http://users.rcn.com/fcohen/Polaroid.htm
If those are too thick; try:
http://www.powerstream.com/thin-lithium-ion.htm
http://www.infinitepowersolutions.com/product
Miguel