Re: [iPAQ] H38xx power drain problems

Am Mo, den 19.01.2004 schrieb Philip Blundell um 23:30:
> On Fri, 2004-01-09 at 22:36, Nils Faerber wrote:
> > Reason for my reasearch was to find this nasty power drain problem still
> > persisting in H38xx iPAQs, i.e. consumption of 25% up to 50% within 12
> > hours (and more). This reduces the usability of the devices
> > significantly.
> I just experienced some slightly strange behaviour on my h3900, which
> might be related to this. The ipaq was sitting quietly on my desk,
> suspended, and had been that way for a couple of hours. All of a sudden
> it woke up for no apparent reason, and sat there for a few minutes until
> ipaq-sleep suspended it again.

Strange.
Sure you have not had a user RTC alarm set?

Oh... this brings me to a bug in atd I have to fix which prevents your
time/alarm applet from doing repeated alarms...

> If this is happening often, it would obviously cause abnormally high
> battery drain. Perhaps we should add some extra instrumentation to the
> wakeup handling code in h3600_asic_battery.c to find out what the cause
> of these mysterious awakenings might be.

This might indeed be a problem. But maybe we should first try to find
out, without much hassle, if this does really happen. Maybe a simple
resume script which notes the resume date/time to some log. So you would
easily be able to trace if there are more of those wakeups.

I plan on doing this, now, and also want to modify the battery charging
algorithm a bit. I intend to add a /proc interface to the charger logic,
maybe /proc/asic/charger with three possible values:
0 - force charger off
1 - force charger on
2 - automatic

I also think that the charging threshold, this 10mA thing, is utterly
wrong. First this does no good to LiIon batteries. They do not like it
very much to be fed up to the limit all the time. The last 5-10% (i.e.
90-95%) are very critical. Most charging circuits reduce the charging
current to very low when entering the last 10% (to be charged). Likewise
it is also recommended that LiIon batteries must not be fully charger
again unless they have lost a certain amount of capacity; mostly the 10%
threshold is used again. This means that charging should only be done if
the capacity drops below 90%.
I will also try to change this once I have the above change in place ;)
The effect you get when you always charge the battery is the "lazy
battery" effect, i.e. you get a reading != empty (even more than 50%)
but any higher than usual battery load, e.g. WLAN, would cause a battery
fault - this what happened to an older H36xx iPAQ now :(

Oh well... I see what I can do ;)

BTW: Want to build our own PDA???

> p.
CU
  nils faerber

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