Small 12V Sources?

[Chad1]

Hey guys. Would really appreciate some advice from the community...

My question: What's the smallest power source that can supply 12V and ~120mA?
Background Info: I've been working on a fun little doo-dad which essentially drives a 12V Radioshack computer fan inside an ABS project box. I'm currently using a 9V battery in series with two AAs to supply the 12V and ~120mA necessary to drive the fan. But the battery/fan size make the doo-dad's footprint (i.e. th project box which houses the fan and batteries) larger than I'd like. Even a 1.5" computer fan (the smallest I can find) uses 12V and ~110 mA, so I'm stuck with these specs. I thought about using a couple of 3V coin cell batteries and using a switchmode supply to boost it to 12V, but I don't think I can get enough current out of them. I'm in need of some ideas for small power sources which can deliver the aforementioned specs. Ideally smaller than a single AA, if such a thing exists/can be done.

[sleemanj]

I'm in need of some ideas for small power sources which can deliver the aforementioned specs.

Small LiPo cell and a boost converter would be your best solution I think.

Even a 1.5" computer fan (the smallest I can find) uses 12V and ~110 mA,

Is the fan size important?

These are 1.5cm each side I believe (a little more than half an inch), 5v, 60ma
http://www.aliexpress.com/item/FANS-HOME-Sepa-1-5-1505-5v-0-06a-remote-control-car-motor-mini-small-fan/865168271.html

I have some coming in an order soon, I just wanted to see such a tiny fan :-)

[pa2ees]

What about powering the fan with 6V or 8V? If the fan is a DC (not pwm) fan, it might run slower, but it will still run.  It's just a thought.

 - Erik

[mariush]

The fan will run with smaller voltages, it will probably even run at 5v but at low speed.

Forget about cr203* batteries, they're designed for <10mA of current. 
Forget about powering the fan from a 9v battery, it's expensive and low capacity and if you want them to last you shouldn't draw more than 100mA constantly.

I'd suggest changing design to a 4xAA or AAAA batteries. With rechargeable batteries, the maximul voltage will be about 5.4v which is below what most microcontrollers and ICs can handle.
If you use regular batteries, you may want to use a low drop regulator because 4 regular batteries would give up to about 6.5v which is a bit more than some microcontrollers and ICs can handle.  You can find 5v ldos that have only 0.1-0.2v drop so they'll do 5v fixed just fine. Or you could use a LDO in both cases to drop to 3.6v or some lower voltage.

The fan should run from 5v but at low speed. You could go for a cheap lm25** boost regulator (you can find them on eBay for a couple of dollars) to boost the 4-6v to 7.5-12v
 

[pa2ees]

Another battery option is a regular lithium cell, not a coin cell. You can get lots of current from them for a boost converter, and they have a good amount of energy for their size, so it would be smaller than 4 AA cells. Plus they're rechargeable, and you can get them from a hobby shop. You could find some smaller than a single AA cell, but it would have to be recharged/replaced more often.

 - Erik

[tszaboo]

Ebay 12V wall-wart power supply? USB + Traco 0512?
Does it have to be move-able? If you go with battery power, than I would put in a temperature switch and a fan controller, because power saving.