Hello, Surface Forum! I'm a grad student, who'll be collecting data in an open-field environment this summer (Southern hemisphere). Will the core M3 SP4 last me an entire day with the wifi off (~12hr) 0n a single charge? (If not, is there a way to charge it using battery banks?) I also need recommendations for a case with a water bottle holder (standard 500ml). I'd prefer a messenger bag/sling bag; something ultra light and thin (I plan to leave my backpack on the vehicle, bringing only the carry-on for doing active field work). Thanks, and Cheers!