By w/h, I'm sure you mean Wh, which is a unit of charge. (W/h is something completely different, and mostly relevant for how a quickly power source (like a pow

By w/h, I'm sure you mean Wh, which is a unit of charge. (W/h is something completely different, and mostly relevant for how a quickly power source (like a power plant) can meet variation in power loads.) As for the rest of your explanation, it's actually NOT a good reason to label batteries by Ah or mAh over Wh. Wh is better for almost any purpose as long as it can be accurately determined. You still have to provide the voltage it is designed for, but it is just as easy to find the Ah's in a battery from the Wh as the other way around, when you know the voltage. The problem, though, is that the true voltage of a battery isn't constant, but tends to vary depending on what load you connect to it. This is because of every battery having an INTERNAL resistance (R_internal). This internal resistance will (for a basic cell) lead to a reduction of the delivered voltage (as seen by the load) by U_load = U_nominal - I*R_internal. Also R_internal can increase if the battery is cold, hot or has some defect. This means that the Ah unit provides a more precise measure for the capacity of a battery than Wh.