Yep battery carriers, also rechargeable (li-ion) batteries (you need to read up on them though), I also have a cotton pickers charger (usb, voltage readout) for traveling. Then - TRITS, TRITs, TRITS. Tritium vials that are installed with Norland 61 (UV cured) - so that the light is visible at night.
I have a (modded) AA powered Surefire L1 that has a trit in the "clip" portion of the pocket clip - makes it easy to spot in the hotel bedside table.