If you’re a soldier doing reconnaissance in enemy territory, you’ve got a lot of problems. Taking fire, staying invisible, and enduring the elements are obvious. Battery life is a little less so. The idea that propane is a solution to these woes? That sounds crazy.


And yet, battery life remains an increasingly cumbersome struggle that the military faces. As American soldiers become increasingly reliant on technology, they demand more power sources. One dependable option is the standard Ultralife UBI-2590 battery, pictured below. Weighing over three pounds a piece, these brick-sized devices can power anything from a radio to an antenna to a smartphone. But since the batteries have a limited capacity, soldiers need more than just one for a mission. They might need a few dozen. After all, there aren’t many wall outlets for recharging in the mountains of Afghanistan.


Enter DARPA. With the support of DARPA’s Trans App program, a team of engineers from Ultra Electronics built a lightweight, 350-watt propane generator that’s capable of charging in batteries in the field. It’s also practically silent. At a recent DARPA demo day the team showed me the invention, which isn’t much bigger than a duffel bag. I had to ask if it was running. (It was.)

At first, a propane-powered generator might not seem like such a game-changing innovation. But consider our recon soldiers camped out in far flung locations, transmitting potentially life-saving intelligence while struggling to evade detection. Once they’re out of battery power, the soldiers can’t do their job. Firing up a gasoline-powered generator would give away their position, and dropping more batteries into the area risks lives. So these soldiers lug in as many charged batteries as they think they’ll need—sometimes adding nearly a hundred pounds to their already heavy load of gear.

Propane is not nearly as heavy as lithium ion battery cells. Thanks to the impossibly quiet new DARPA-funded generator, soldiers can carry in a few batteries and recharge them on the fly. To give you an idea of how much weight this new invention can save, check out the illustration below. On the left are 100 UBI-2590 batteries. On the right is the equivalent amount of gear a soldier would need to generate the same amount of power on a mission:


Bear in mind the simple, brutal fact that each of those 100 batteries weighs over three pounds. The propane generator weighs just 11 pounds, and the tank weighs an extra 20. Smaller four-pound tanks work just as well.

Effectively, DARPA wants to replace dozens of pounds of gear in a soldier’s pack with just a few pounds of propane. It sounds like an ambitious but simple goal, one that could save lives. Now if they could juuuuuuuuust figure out how to turn fatigues into a giant solar cell, nobody would have to carry any power sources at all.


Images by Adam Clark Estes