Using mAh to represent energy capacity works fine within a small circle of products—mainly devices that use single-cell Li-ion batteries, along with their accessories. When you mix in categories that use different battery chemistries or multi-batteries—laptops, drones, RC toys, power tools, etc.—mAh is no longer a reliable metric for comparing capacity. Instead, use the watt-hour (Wh) unit of measurement, which builds the nominal voltage into the value, resulting in a proper capacity rating. Watt-hours are agnostic to battery chemistry or multi-battery configurations. A 50 Wh battery bank has the same energy capacity as a 50 Wh laptop battery, which has 5x the capacity of a 10 Wh smartphone battery.