mobile

I'm interested in how I can predict the future battery life of a smartphone after a certain number of days of usage(not number of cycles or decrease in mAh). This is somewhat important in the debate of user removable vs sealed in batteries. Or when deciding if you want to buy a phone with a sealed in battery.

I did not really find any such method online, so I came up with the method below. It assumes a constant degradation during use, so its probably somewhat inaccurate.

The degradation factor is based on Apples claim that 500 cycles gives 20% degradation, so the average degradation factor must be 1 - 0.8^(1/500) = 0.000446.


Method for calculating degradation of battery life:

D = dPT

D: Degradation in percentage of original capacity or battery life.
d: Degrading factor, assumed constant. (typically 0.000446)
T: Time (e.g number of days)
P: Power consumption in share of battery per time (typically %/day)

New battery life can thus be calculated as:

l = L(1-D)

l: Battery life (when user is awake) in end of period.
L: Battery life (when user is awake) start of period.



Example of use:

Jon wants to know his battery life in one year from now.
He estimates his initial battery life (during the hours he is awake) to 12 hours.
His battery drains in total 150% during a typical day(including night) of use.
He assumes a degradation factor of 0.000446.

Hence:

d = 0.000446
T = 365 days
P = 150 %/day
L = 12 hours

D = dPT = 0.00045 * 150 %/Day * 365 days = 25%

Thus the new battery life will be:

l = 12 * (1 - .25) = 9

So his new battery life is 9 hours after one year of use.

Do anyone have comments? Or know better ways of doing this? :confused: