Why does the first bar of the battery life take 36 hours to go away, and the other 3 seem to vanish in 10 minutes? How do my calls get dropped when I CLEARLY have full bars? Read on m'friend.
We're in a world that sends robots to outerspace, has cured innumerable diseases, and FINALLY allows us to play Super Monkey Ball using accelerometers on a portable device - you'd think we'd be able to measure the amount of charge on a battery. Truth is, we can - and accurately too. But you'd never know it in your every day life...36 hours to dissipate all the power, but plug it in for 10 minutes and miraculously it appears that you're back to full strength? How can that be? We all know it's not actually back to full (or >80% as the bars would suggest), so what is actually going on? Marketing.
Like everything else, that battery meter is controlled by software, and that software is controlled by humans - at least for now. In related news...
Signal vs. Noise
We all know AT&T's pitch, "More Bars in more Places," but what does that really mean? We've also all had calls dropped only to look down at the phone to notice "full bars." The issue is that the meter only tells one half of the story.
When your phone is on standby and you're likely to look at the meter, those "bars" are the combination of two factors: the raw signal strength received from the cell tower, and the signal to noise ratio (the SNR) - essentially, how well the tower can hear your phone based on how much other noise (data) you are competing with. The SNR is by far the most significant component in determining call quality, but because the SNR is constantly changing the phones display a blend of the two measurements, and are set to give far too much weight to the signal strength of the tower.
When you are actually on a call, your phone and the tower are in in two-way communication, and the meter reads more precisely, but you're generally not looking down at the meter at those times.
When you see full bars, what you're seeing is that your phone is hearing the the local signal loud and clear, but what is not shown is if the tower can hear your phone shout back. Throughout your call, the amount of data being sent to your tower can change frequently, and when a deluge hits, it's as though you're pissing into a waterfall. In this case, you're not actually being lied to, just selectively informed. More marketing.
All your Base are Belong to Marketing
It's a lot easier to sell phones that are always charged and always transmitting full signal strength. Working with the truth is hard. As it turns out, the firmware on many phones artificially inflates both the battery meters AND the signal strength. It's like bad politics, once one candidate goes dirty, the other candidates have little choice but to lie back, and so the cycle continues. Why else would we need so many 3rd party battery monitoring apps? (sampling here)