Rockbox General > Rockbox General Discussion

Dap Playing Time

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robin0800:
It would appear that dap playing time, is directly dependant on battery capacity. The current used at least in the case of the ipod iappears to be hard coded.

Two Quick questions:

1) What is the ipod battery capacity set to?

2) What Is the value of the current used?

The Above assumes
Playing Time = Battery Capacity/Current used

frause:
1) I don't understand what you mean by "set to" but here is a table with ipod battery capacities http://ipodbatteryfaq.com/ipodbatteryandpower.html

2) The current drawn varies. For example with the backlight on and the disk spinning, the current drawn will be much higher than idling with no backlight.


--- Quote ---The Above assumes
Playing Time = Battery Capacity/Current used
--- End quote ---
Thats correct. That means that if you know the playing time you can calculate the average current. (assuming a healthy battery using it's full design capacity)

Thus, a new Ipod 5.5g 30GB playing for 8 hours from full to dead battery would be drawing approximately an average of 400mAh/8h=50mA.

I believe there was someone who measured the power drawn on some kind of ipod. Maybe search the forums?

robin0800:
Correct!that is exactly my understanding of it.

using patch FS#7070 to set 600mAH
results in the battery display time being halved any ideas

soap:

--- Quote from: robin0800 on May 15, 2007, 03:12:03 PM ---It would appear that dap playing time, is directly dependant on battery capacity. The current used at least in the case of the ipod appears to be hard coded.

--- End quote ---
The battery capacity value (now fixed in SVN) has nothing to do with the amount of current drawn.


--- Quote from: robin0800 on May 15, 2007, 04:28:40 PM ---using patch FS#7070 to set 600mAH
results in the battery display time being halved any ideas

--- End quote ---
It would, if you consider the fact I believe the value was 1300 before.

The time displayed is an estimation, based upon factors including the battery capacity, and a mapped discharge curve for the player/battery.  That patch you used fixed one of these factors, but the discharge curve still needs to be fixed.  A bicycle with one good wheel isn't much more use than a bicycle with no good wheels.  

The time displayed has absolutely nothing to do with how much power Rockbox consumes or how long your battery will last.

lights0ut:
I don't think that this is much of an issue, I don't view time remaining (even now on my new Gigabeat) as it is inaccurate. I prefer to see battery life in percentage because it gives me a better guess at how much time is left. If I paid attention to how long my iPod lasted during a regular days play, I'd say there was about 6-9 hours playtime depending on use. Now for simplicity's sake lets say the average is 8 hours, so at 75% you have 6hrs left, at 50% 4hrs and so on. Doing simple math is really not that inconvenient. Plus the percentage display takes up less room on the WPS than the time remaining.

On the inaccuracy of the time left: I remember booting my iPod with about 50% left to see that the time left would say 45m , then 10m later, when the player was idle, it would say 3h40m. IIRC, percentage just measures voltage from the battery as a percent of the voltage from a full charge, so it is more accurate since it does not factor in any drainage curves.

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