battery advice needed

Hi, Im just starting a project to turn my monome ( wireless using a la fonera box. My main problem is powering it all. I really like the look of the lithium stealth backpack but im in the uk and it comes to $80 with shipping! What alternatives are there out there? Am i being unrealistic need to power a matrix of 64 leds and send and recieve serial via the la fonera and aslo find a way to power that. I don''t mind having a sepearte power for the fonera but one solution would be ideal.

EDIT: Just to make myself clear: im using an arduino connected to a button matrix and an led matrix both 8x8. How can i power the arduino via a battery? Thanks a lot, Steve

Here are a few links:

Cheers for the reply. I don't really understand the phone battery one, seems starnge how 3.6v can be used to power 5v with no step up.

The 9v battery seems like a reasonable soultion, im just worried about how long it would last?

If anyone else has other suggestions, let me know.

Thanks a lot

To get 5V from a lower voltage, you use a step up converter, like this one: or this one

Indeed, the 9V won't last much, especially in your case where you drive a bunch of LEDs.

thanks :) just saw a video of someone whoe connected a cordless drill battery to the arduino through the power plug, looks interesting. Just seen these and im wandering if i could use any of them and which would offer the best battery life. A bit more info on my circuit: it basically scans rows of leds 8x8 saw at most 8 leds are lit at once and then its just the serial stuff going in and out which will eat up battery. so i guess itd be rated at about 200-300mA.

The last two are the most apealing because they can be recharged.

Thanks a lot

I don't really understand the phone battery one, seems starnge how 3.6v can be used to power 5v with no step up.

He's just being lucky with the atmega tolerating the lower voltage. Try this with some serious load on any pins and unexpected things will happen. 8MHz can run reliably on 3.6V - 16MHz can't.

The easiest way to know how much your device is taking is to measure the current (average). The 9V 1.2Ah battery you pointed to is not very powerful. I would rather use 4xAA NiMH batteries, 2.5Ah, in series (4x1.2V = 4.8V), like these ones:

And you can connect them directly to the Vcc, no regulator or step up converter. They should last for 8 hours of use at 300mA.

That's great thanks. I've just hooked up the 4xAAs. Works a charm!