description of battery level calculation updated
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@3019 a1c6a512-1295-4272-9138-f99709370657
diff --git a/docs/CHARGING_ALGORITHM b/docs/CHARGING_ALGORITHM
index 7bbdd60..928adef 100755
--- a/docs/CHARGING_ALGORITHM
+++ b/docs/CHARGING_ALGORITHM
@@ -8,10 +8,11 @@
[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 @@
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]