The USB Nugget Power Adapter is one of the most practical pieces of kit you are going to run across. It allows you to harvest power from BA-5590 and BB-2590 batteries, with two USB ports (2.3 amps) as output. You can run lights and charge any number of devices with those left over batteries that don’t have enough juice left to use in a patrol.
Manufactured by Controlled Solutions, Military Hardware is their distributor. While the Nugget is available on Amazon, it’s actually cheaper to buy it direct from Military Hardware.
The full line of gear offered by Military Hardware is available for unit and agency orders through Darley Defense.