The most common drones, the ones you might see down the park, are currently powered by lithium batteries. It is common for one of those drones to have no greater flight time than 30 min. This is due to the energy density of the batteries. Lithium batteries are good, and have got a lot better over the last 6 years. The price is also relatively cheap. However, the quest for more and more endurance is forever present. This has lead to groups of people looking for more energy den