How to correctly calculate the operating time of an external battery to charge the phone?

C

charly2012-07-23 14:43:32

Do it yourself

charly, 2012-07-23 14:43:32

Hello.
Faced with the choice of an external battery for charging a mobile phone on the road. But I realized that the choice is not easy. In this regard, I ask the community for help in calculating the operating time of an external battery.
The parameters of the internal battery of the phone are as follows:
E = 1750 mA * h
U discharge = 3.7 V
U charge = 5V
I charge ~= 0.8A
Then the battery energy W = 6.48 W * h
We take an external battery with x-kami:
E = 9600 mA *hour
U discharge = 5V
I discharge = 1A
U discharge and I discharge correspond to the charging parameters for the internal battery.
Then it turns out that the energy of the external battery W = 48 W*h
Question.
How many times will it be possible to charge the indicated internal battery from such an external battery?
I read many articles, but I could not understand how to calculate correctly.
Thanks in advance.

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3 answer(s)

A

astrobeglec, 2012-07-23
@astrobeglec

Battery capacity is calculated by mAh. In your case, with a charging efficiency of 100%, you can charge 5 times, but with a lower efficiency, respectively, less.

R

R6MF49T2, 2012-07-23
@R6MF49T2

Battery charge efficiency ~65%? from here we conclude - you can charge 3.5 times.

E

elgordo, 2012-12-28
@elgordo

The whole difficulty is that the capacity of the external battery, most likely, will not correspond to the declared one. I assume that you are trying to find a balance between price and capacity. Therefore, I would buy for the maximum capacity, based on the maximum amount that you are willing to spend.
As for the calculation, given the existence of the law of conservation of energy, simply divide the capacity of the external battery by the capacity of the internal one. Imagine that the charge will flow from one to another (in fact, this is the case, similar to vessels with liquid, capacity = volume). The phone uses PWM for charging dosage, i.e. There shouldn't be any waste of energy. Well, as already noted, part of the energy will be lost in the process of transformation.