Quote:
Originally Posted by Katsunami
The lifetime does depend on the device, though.
Let's say that for each year a battery loses 25% of the capacity it has remaining. (I'm just making these numbers up, but it illustrates the point.) Then you will get this use out of it:
Year 1: 100%;
Year 2: 100 * 0.75 = 75%
Year 3: 75 * 0.75 = 56%
Year 4: 56 * 0.75 = 42%
Year 5: 42 * 0.75 = 31%
A laptop battery that starts out with 6 hours of usage will have declined to a maximum of two hours of use after 5 years. While still usable, it can be a pain in the neck.
A Kindle on the other hand, starting out with 6 weeks, will drop down to 2 weeks of usage. That's a huge drop, but an e-reader which lasts for two weeks is still perfectly usable.
I've noticed that, after three years, I'm starting to see the "Your Kindle is almost empty"-warning. Previously, I never saw it; I've always connected the reader to the computer to upload books before it appeared, keeping the Kindle charged perpetually. Now I don't seem to be able to manage this anymore. (I'm not reading slower or more books between charges AFAICT.)
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Math is not entirely true,
To say year 1 you have 100%, year 2 only 75%, 3 50, and 4 25% would be more true,
Why?
Because you end up charging a 50% battery more frequently, than a new one!
I've always said this to my froends owning li-ion cellphones:
When you can charge it, keep it plugged in!
My friend, who is of the opinion to fully drain his li-ion before charging every month or two, went through 2 batteries already, and is always seen with a battery pack.
Me, I have my phone always plugged in, with a low power 800mA charger.
In the office, bedroom and car.
I basically only unplug it from the bedroom to the car, and car to the office.
I'm in my 3rd year on my original Samsung Galaxy Mega battery, which has between 75 to 80% of new capacity.