We hope this post assisted you in making better 

use of outdoor power and enjoying nature. 


April 29,2020

How to calculate the time of outdoor power supply to power the equipment?

As the weather begins to warm, an increasing number of individuals prefer to go camping on vacations. At the current moment, an outdoor power source is a useful piece of equipment that may assist us in powering our electronics while we are out in the wilderness. But how do we know how long we can run our equipment on our outside power supply?

With over fifteen years of the energy industry background, CTECHi is committed to providing the most reliable, most innovative, and premium all-in-one sustainable power solutions for all kinds of off-grid life and power backup needs.

Firstly, we need to know and understand two concepts.

  • Ampere-hour: An ampere-hour is a unit of power that indicates the capacity of a battery.

  • Watt-hour: A watt-hour is an energy unit that represents the amount of electrical energy required by equipment per hour.

We can't just use ampere-hours to describe the capacity for batteries with varying voltages.

A 20Ah device, for example, may handle a voltage range of 12-24V; in this case, a 12V20AH battery is used to power the device, which can provide power for 1 hour. At this point, connecting two such batteries in series would result in a voltage of 24V20AH, and we will see that the ampere-hours do not increase, but the duration of the power supply doubles. Therefore, we can use the standard capacity work, W(work) = P(power) * T(time) = I(current) * U(voltage) * T (time).

That is why we usually use watt-hours to calculate the time taken by the outdoor power supply to power the equipment.

Second, you should remember that when we use the outside power supply, the cooling fan, inverter, and other accessories inside the outdoor power supply are also operating at the same time, resulting in a loss estimated to be around 15%. You may ask the vendor or look it up on the internet to find out how big your outside power supply loss is.

Example: 518Wh outdoor power supply for a 45W small refrigerator, power supply hours = 518Wh * 0.85/45W = 9.78Hours


Lastly, if your device is only marked with mAh and voltage, please use the formula W (watt-hour) = q (mAh) / 1000 * U (voltage) to calculate the watt-hour first, and then the power supply length as 1Ah = 1000mAh.

Example: 100000 mAh for a 3.2 volt device, Watt hour = 100000/1000*3.2 = 320Wh

320Wh = 320W*1Hour

power supply hours = 518Wh*0.85/320W=1.37Hours