The time a battery can deliver power, also known as the runtime, can vary depending on several factors, such as the capacity of the battery, the load (the electrical device it is connected to), and the efficiency of the battery.

The runtime of a battery is determined by the capacity of the battery, expressed in Ampere-hour (Ah), and the current requirements of the connected device, expressed in Ampere (A). To make a rough estimate of the runtime, simply divide the capacity of the battery (Ah) by the current requirements of the device (A). This gives an indication of how many hours the battery can supply power before it is completely discharged.

However, it is important to note that the actual runtime can vary due to various factors. Firstly, the actual capacity of the battery may be lower than the specified capacity due to aging, environmental conditions, and other variables. Secondly, the load can vary over time, which affects the runtime. For example, a higher current requirement will result in a shorter runtime.

Additionally, the performance of the battery can be affected by environmental factors such as temperature. Batteries generally have reduced capacity at low temperatures, which can decrease the runtime.

Therefore, it is advisable to consult the specifications and recommendations of the manufacturer of both the battery and the device for an accurate estimation of the runtime. Based on that information, you can get a better idea of how long a battery can deliver power in your specific situation.