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Subject: Re: "Estimated Runtime" feature.

Re: "Estimated Runtime" feature.

From: Paul Louden <>
Date: Tue, 17 Apr 2007 15:40:30 -0500

To my understanding, 20% actually means "you have 20% of your total
time left" because we base it on a discharge curve rather than strait
mappings to voltages.

Meaning that percentage is an accurate value. The problem with times,
is that they're only accurate for new batteries, while playing MP3,
without skipping. Once you start moving from the usage pattern used to
determine that runtime, it becomes meaningless, or at least much less

Remember how many complaints people issued when the "Runtime
remaining" only said 9 hours, shortly after the H300 battery fix?
People assume that it's somehow calculated based on current power
consumption rate, rather than simply being "We expect it to last a
total of 16 hours, you have 80% left, 0.8 * 16 = 12.8, so 12 hours, 48
minutes" (which is, I believe, all that's done now, with the "we
expect it to last a total of 16 hours" being based on what you've set
as your battery capacity).

In my opinion estimating remaining time is misleading under this sort
of circumstance, and a user can go from 80% to "about 12-13 hours" in
their head if they really do get 16 hours total, and if they get 10
hours total because their battery is old or they use FLAC, they can
just as easily jump to "Oh, 8 hours left" rather than thinking that
there's 12.8 hours remaining and then finding out that they've used up
their battery when they expected it to have around for the ride home
from work.

As I said, I see it as being "nice", but ultimately about as useless
as the old % volume. Makes sense on a strictly intuitive scale, but
nothing really practical about it, unless (in the case of the battery)
you meet the same conditions as the runtime estimate represents.
Received on 2007-04-17

Page was last modified "Jan 10 2012" The Rockbox Crew