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Nokia Phones
R. Alex Whitlock
What's the point in having a powerometer on a phone if it's going to say "full power" for two days of chatting away and then dwindle from "full power" to "low battery" less than two hours? My old phone had this problem and, unfortunately, my temp phone has the same thing.
Observations
The power meter is a good idea in principle.
The problem is that the twit who designed it didn't factor in any "expected battery life" calculations, preferring to rely on the battery's voltage reading - and probably just designed one program for a whole multitude of phones rather than a specific one that would take into account the characteristics of the battery pack for your particular phone.
As anyone who's ever paid attention to battery chemistry knows (read: nerds like me), reading the voltage is the worst possible way to tell how much charge a battery has - especially in the NiMH / Lithium type batteries commonly used in such portable devices.
To sum up, you probably have a two-cell battery, NiMH, and the person therefore set the "full" reading around 2.5 V or so.
Fully charged NiMH is about 1.45V per cell, of course. They vary with charge capacity on a known curve from there however; at 20% discharge to about 80% discharge, they only move down from 1.3 volts to 1.24 or so. Then from 90% on is when they just tank and start dropping like crazy.
Now, your battery charger (we hope) also has a little detection circuit to tell when it's finished charging your NiMH battery. Because NiMH batteries get high, then start descending again on overcharge, and really do NOT like to be overcharged (as opposed to the old NiCd rechargeables which would take trickle-charging all night with no complaints, but have problems with storage capacity and developing "memory").
The batter is Lithium Ion, but thanks for the info!
Li-I's have an even flatter voltage curve. The explanation holds even better for them.
I've always had pretty accurate readings on my cell phone. Maybe some phones are better at calculating remaining life than others.
I know palm devices use different algorithms to calculate remaining battery life, depending on the type of battery (and if you go into the secret "dot palm" command set, you can change the settings). I can't imagine that phones, at least higher end models, which have been around much longer, don't employ something at least as sophisticated as early palm devices.
Kevin,
You'd be surprised where they cut corners :) Plus, Palm devices have been around a LOT longer and have access to higher-power CPU's able to run the somewhat intensive algorithms in the background that take into account not just the type of battery and the current reading, but also the estimated and stored previous usage curve and readings of how much power has actually been used.
Cell phone? Nah. They just read the voltage curve, and if they set the reading scale down just a tad from where it should be (as little as 0.1 volts for Li-I), it'll remain stuck on "full".
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