Introduction
While related to each other, Amp hour (Ah) and Watt hour (Wh) represent two different electrical phenomena in solid state batteries. Amp hours is a measure of electrical charge, while Watt hour is a measure of electrical energy. Amp hour shows the amount of electrical charge of a battery (or a semi solid state battery), or what we usually call the battery capacity. Watt hours, on the other hand, is the total amount of energy a battery can provide, which is a combination of the battery’s amp hours and its voltage.
Table of Contents
Difference Between Ah and Wh
Amp hours refers to the amount of the current that can be drawn from a battery in the duration of on hour. So a battery rated at 66Ah can theoretically provide 66 ampere for 1 hour, or 1 ampere of current for 66 hours. You may know ampere hour as the nominal capacity of a battery which is written on its label. So for a 6S 32000mAh solid state battery, the ampere hour or Ah equals its capacity which is 32000mAh.
On the other hand, Watt hour is the total stored energy of the battery, which is a combination of the both ampere and voltage. So a more meaningful metric that can be used to compare different models of batteries is to refer to their Wh/kg or their energy density. So for example, a 6S 27000mAh solid state battery has 640Wh energy, while a 12S 27000mAh solid state battery has dual energy of equal to 1280Wh. This may not be a good measure because these two models both have around 272Wh/kg energy density.
How to convert Ah to Wh
In order to convert amper hour to watt hour, you need to know the voltage of the battery. And if you multiply the voltage of the battery by its Amp hours, you will get the Watt hours of the battery. For example, for a 6s 22000mAh solid state battery, its amp hour is 22Ah, or in other words, it has 22Ah capacity or electrical charge. Since it is an ultra high voltage model, it would have 3.95v/cell nominal voltage, leading to a total of 6×3.95v=23.7v output voltage. Consequently, the Watt hours of this model would be 22Ah x 23.7v = 521.4Wh.
Inversely, to convert the Watt hour to Amp hour, you should divide the number by voltage of the battery. For example, for a 6S battery, if we know that its Watt hour is 948Wh, by dividing the Wh by the battery’s voltage which 23.7v, we would get 948Wh / 23.7v = 40 Ah. So the Amp hour or capacity of the battery is 40000mAh, and it will be a 6S 40000mAh battery.
You can see a few more examples of conversion between Ah and Wh, as well as the Wh/kg value, for a few different models with different capacities and different numbers of cells:
| Model | Ampere Hour (Ah) | Watt Hour (Wh) | Energy Density (Wh/kg) |
| 7S 35000mAh battery | 35Ah | 968Wh | 237Wh/kg |
| 14S 44000mAh battery | 44Ah | 2433Wh | 237Wh/kg |
| 18S 66000mAh battery | 66Ah | 4692Wh | 299Wh/kg |
| 24S 66000mAh battery | 66Ah | 6257Wh | 297Wh/kg |
