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Graph of the iPhone battery life vs Time


Well-known member
Jun 13, 2010
Wait, so you mean to tell me that using the phone at 20% and having it drain more power (phone call) than from 30-20% is abnormal? **** and I was here thinking my phone would charge by itself when I used it to call people.

Before you say the phone dies too fast, this phenomenon does not occur with my phone, I could use it normally from 20-0%. Perhaps in this unscentific test of sorts, the signal was low and the phone tried everything to keep the phone call alive.
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Well-known member
Oct 7, 2009
nah.. even though when i had my 3G it was a POS but did not drain any faster after it hit 20%

IF any of these so called findings were true it would be all over the web. the sad thing is some people are so naive they might actually believe this and discourage them from buying an iPhone


Well-known member
Jun 10, 2008
coming from a background in public-safety communications systems, there is a very distinct problem with the "battery meter" on MOST electronic devices.

quite often, the "Battery Meter" is a gauge based on Voltage, rather than Amperage. Since voltage gradually decreases, although not in a linear fashion, as the voltage gets low, the battery dies quicker. whereas amperage does decreases in a more linear fashion.

to see this best... take a glass of water that is full. that will be our battery... poke a hole into the very bottom of the cup and watch the water flow out...

the force of the flowing water is voltage, the volume of water is amperage.

as the water drops to the bottom of the cup, the force of water decreases, and eventually trails off. but the force slows down as the water level in the cup drops. THUS the voltage drops, and the meter shows to the best of its ability show the "level" of the battery.

there are a few battery technologies which show the actual level of the battery, but the battery is much larger than original batteries, and the chargers get very large and complex too. There is a technology used by Motorola called by Motorola, IMPRES, whereby the charger working with the battery, actually measures how much amperage goes in and out of a battery during charging and use. those batteries are most probably the best check of actually battery capacity.

Apple DOES use similar technology in their Laptops, see MacBook / MacBook Pro: About This Mac --> More info... --> Power --> Charge Information will show Charge Remaining, and Capacity, both are mAh measurements, or milliAmperage Hours

hope that helps..


Apr 23, 2011
So one study tells it all. That's some thorough research! How many iphones in the test? Under what conditions? Were they fully charged before start of test, partially charged? That's like saying I bough a certain brand of tires and 5 went flat at 15,000 miles, therefore all their tires will go flat at 15,000 miles. No details for that study. That's what we call as quack science.
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Well-known member
Jan 17, 2011
Last time my battery was around 20% and I made a call, my 3GS lasted longer than I expected. I feel like having the screen on wastes more battery than being on a phone call does. I was on EDGE though, that probably makes a bit of a difference.


Well-known member
Jan 11, 2010
graph is meaningless... so the guy starts making a call at 20% left... OF COURSE it's going to drain more quickly then if just sitting idle...


Well-known member
May 31, 2011
I'm commenting here, since my comments reflect this and not the original thread where this was linked in.

I find this graph odd in my case, as I've thought the iPhone stays alive for a long time once it reaches 30% or below. I can last on 20% for a good while, and have some time once it reaches 10% as well. Much better than my old blackberry, once it says low battery I better plug it up because it's going to die ASAP.