I'm looking to power my new Arduino project from a power tool battery. Right now I have a few options ranging from 3.6V to 9V batteries. Is there anything that I should watch out for before trying to hook up the battery directly to the board? Ideally I'd just like to hook up the board to the terminals on the outside of the battery with minimal modding.
Thanks!
Use something 7V or over, and under 20V. Should work when connected to the DC connector then.
You need to be careful of the power dissipated in the
regulator.
The power dissipated in the regulator is (Vbattery - 5V) * I
where I is the amount of current you will draw from the
regulator in your application.
IIRC the minimum voltage required by the Arduino is around
7V. The minimum efficiency is 5/7. At 9V in your are at 5/9
which means close to half of the power is wasted heating
the regulator.
(* jcl *)
jlucianai, I've been looking at the articles from here: http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html
I don't have any prior experience with this sort of thing, so will that mean that I'll need to include a heatsink on the regulator? I'm not entirely sure what this will entail 
Or, is there some sort of additional voltage regulator or rudimentary power supply I'll need to create? There should be around 4-5 sensors attached to this that will need to be powered, including a 3 or 4-axis accelerometer.
Thanks for the help!
If all you are powering is 4-5 sensors and an accelerometer
you probably won't have a problem (at 9V).
Get the datasheets for each sensor and the accelerometer
and add up the currents. See if the Arduino documentation
mentions power dissipation and input voltage.
Since I use my own boards I am not familiar with the Arduino
regulator. I did writeup a FAQ about linear regulators --
http://wiblocks.luciani.org/FAQ/faq-rtheta-ldo.html
(* jcl *)