If you do any operations in the military today, you will be carrying mostly batteries. The batteries you carry will probably be equal in weight to the amount of ammunition and water you carry, depending on what types of operations you’ll be doing. If you’re lucky, a vehicle will be carrying most of your batteries, but if not…
Flashlights, short-range civilian radios (so military nets don’t get crowded with squad- or platoon-level talk), GPS devices, and on and on– all of it powered by batteries of different types. The Army is experimenting with solar-powered stuff these days and I hope it turns out to be promising, because we all want a break from the batteries.
And, oh, of course– the batteries you lug around with you in the hot sun all day, the ones you use to replace the batteries that just ran out in your device? Yup– 50-50 chance they’re just as dead.