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description of battery level calculation updated

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@3019 a1c6a512-1295-4272-9138-f99709370657
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Uwe Freese 2002-12-18 19:39:13 +00:00
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39
docs/CHARGING_ALGORITHM
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@ -8,10 +8,11 @@ some information here, write to mail@uwe-freese.de.
[INTRODUCTION]
This doc describes how the charging works for the recorder. The algorithm can be
found in firmware/powermgmt.[c|h]. Debug output is done in apps/debug_menu.c.
Charging for the player is done by the hardware and therefore isn't implemented
in rockbox.
This doc describes how the charging works for the recorder. The algorithm can be
found in firmware/powermgmt.[c|h]. Debug output is done in apps/debug_menu.c.
Charging for the player is done by the hardware and therefore isn't implemented
in rockbox. Only the functions that calculate the battery level are also used
for the player.
All following information is related to the recorder.
@ -154,25 +155,21 @@ power consumption, a usual constant value is used. If the LED backlight is set
to always on, it is also considered.
[BATTERY LAZYNESS]
[BATTERY DISPLAY HOW THE USER EXPECTS IT]
The battery voltage gives no realistic hint to the actual charging status when
the charger was just turned on or off.
To not confuse the user with the shown battery level, some tricks are used in
the battery level calculation (this does not affect the charging algorithm,
because it uses the raw voltages):
Assume a 50% full battery and then turn on the charger. The voltage goes up. But
the voltage is smaller than the voltage of a 50% full battery when the charging
started at 0%.
To consider this (and make a better remaining time estimation possible), I
implemented the battery lazyness array. It means (in simple words, let's assume
the charger is turned on):
- if the charger is just turned on, calculate the battery status (percentage)
out of the voltage for decharging (even if we actually charge)
- after 20 minutes of charging, calculate the battery status out of the voltage
courve for charging
- inside these 20 minutes, mix the voltage courves (another array in
powermgmt.c tells how)
- if charging is completed, top-off charge or trickle charge is running, always
set the battery level to 100%
- the battery level is only allowed to change 1% per minute (exception: when usb
is connected, is is allowed to go 3% down/min)
- if charging just started (or stopped), ignore the battery voltage for the
first 25 minutes
- after turning on the device, add another 5% to the battery level, because the
drive is used heavily when booting and the voltage usually gets a little higher
after that
[WHICH CHARGING MODE TO USE]