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Subject: Re: some Ideas about Batteries in Powermanagemant
From: Uwe Freese (mail_at_uwe-freese.de)
Date: 2003-01-19


Hello Holger,

Holger Lembke wrote on Sunday, January 19, 2003, 8:34:50 PM:

HL> Ok, the story. My AJBR has a distracting capacity display. If I start using
HL> it, it has 100%. Then the capacity display drops rather fast to something
HL> around 60%. It falls slowly to 40% and 30% sometimes comes back and than
HL> quickly falls down to low percentages and my AJBR stops working.

These quick changes aren't usual. Your batteries or your unit could be
broken!

HL> After looking at
HL> http://www.stud.uni-karlsruhe.de/~usng/rockbox/ladeverfahren.html and
HL> looking at 'static int percent_to_volt_decharge[11]' I think it is easy to
HL> see why it is this way.

HL> The voltage values simply dont give the resultion to get a better idea
HL> about the capacity at the flat part of the discharge curve.

The "resolution" is enough. In the middle part of the courve, the
voltage has a linear form there.

HL> If this is right, could there be a better way of showing the capacity?

HL> Is it possible to calculate it by runtime? Simply have a thread that
HL> checkes the on/off state energy consuming items (hdd, backlite etc), knows
HL> the drain and capacity and does some math?

I also had this idea some months ago. I already started to write a test
version of this kind. But I rejected this idea after some tests.
If you charge/uncharge the batteries completely every time, it may work.
But if you charge/decharge only litte amounts, it will drift off very
quickly.

HL> Or use the history (that from charging) for a better calculation?

In which way? If you have ideas, let us know.

Bye, Uwe.



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