Hello, what's the working current and the working voltage of a flashlight? If three LED and 4.2V-7500MAH batteries, how long will it last?
Therefore, the output rated power is: 9.9 * 0.3=2.97WAccording to the efficiency of 90% calculation, the minimum input power should be: 3.3WYour battery is: 4.2 x 7.5=31.5WhWorking time: 31.5 hours 3.3=9.54.
This time is prerequisite:1, your battery capacity is not virtual standard, and indeed there is such a big 7500mAH, this capacity of our own very difficult to measure Oh;2, your power conversion efficiency can reach 90%;
This problem is analysed, the pressure drop of high brightness LED lamp is about 3.3V per lamp, and 3 LED is 3.3 * 3=9.9V, which are usually used in series.Your battery is 4.2V, so you will use the DC-DC boost circuit, and then do constant current output 300mA.
