I'm looking for a battery solution for the Beagleboard XM, which requires a 5V power supply. I currently have a simple 4x1.2V AA battery pack, but I'm not particularly satisfied with it:
1) It gets overcharged (~5.2V) and activates the overvoltage detector of the machine.
2) I have to remove the batteries from the pack to put them on a charger every time I need to charge them. I'd much prefer a solution that with no separate parts and one in which you don't need to move the batteries around.
The BeagleJuice is the closest thing I've found to what I'm looking for, but there's no version out for XM yet.
I'm embarrassingly electronics-illiterate, so I don't really know how to go about this. Any help?
Answer
Because of regulator dropout, it will be hard to find an ideal regulator that can deliver >1A from four NiMH cells. Low dropout regulators typically have modest power, high power regulators typically have larger dropout.
I recommend you switch to 6 cells (7.2v); however I just don't use NiMH any more, lithium cells are so much better. Search for "protected 14500" on dealextreme.com, these AA-sized 3.4v laptop cells are awesome. The larger 18650 size is good too.
For 5v regulation, try the "Battery Eliminator Circuit" from a model helicopter (search for BEC or battery eliminator on dealextreme.com or a hobby site such as hobbyking.com). These regulators can handle way more current than you will use. eg http://www.dealextreme.com/p/8s-5a-switch-mode-ultimate-bec-ubec-45214
Don't forget you can use your multimeter to measure how much current your beagleboard is actually using, which will let you know both how beefy a regulator you will need, and how long a battery life you can expect (factoring in the efficiency of your regulator).
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