that has a 3000 mah battery, your portable charger has 4000 mah. mAh clearly represents the amount of time that a battery can power your computing device. When it comes to online calculation, this battery life calculator can assist you to determine the time that how long the battery charge will last. Again, as an example, a 1900mAH battery can supply 1900mA of current to a circuit for one hour, and then it will have used all of its charge. Usually a circuit will not demand 1900 mAH of current all at once for operation. Smartphone manufacturers have increased the amount of battery in the past decade and 4000 mAh that was considered as a humungous amount is becoming standard now. For example, a circuit connected with 800 mAh current rating and it is connected to the load of 40 mAh.
Again, mAH, iillliampere-hours, show how many milliamperes of current the battery can supply per hour of use.
If instead of the current you have voltage and watts, then the formula is (mAh*Volts)/ (Watts*1000) = (hours). Then the battery will last for 20 hours. The formula is (mAh)/ (Amps*1000) = (hours). For example, if you have a 3000 mAh battery that runs at 0.2 Amps (0.2Amps = 200mA), then the time that the battery will last for is (3000)/ (0.2*1000) = (3000)/ (200)= 15 Hours. there's gonna be some loss through charging so you will probably only be able to charge it from 0 to … A 6 Cell Li battery on a netbook will last you around 5-6 hours, obviously depending on what applications/hardware your using.