[maemo-users] What is Best practice for Battery Longevity on N8X0?

From: Igor Stoppa igor.stoppa at nokia.com
Date: Fri Feb 15 07:47:34 EET 2008
On Fri, 2008-02-15 at 02:01 +0000, ext Neil MacLeod wrote:
> Igor Stoppa wrote:
> > On Thu, 2008-02-14 at 14:08 +0100, ext Frantisek Dufka wrote:
> >> Igor Stoppa wrote:
> >>>>> n800: 18 days
> >>>>> n810: 27 days
> >>>> Impressive, any details where the savings were done? Is this strictly HW 
> >>>> related and the n800 has same OS2008 version as N810?
> >>> it's both hw and sw; the sw part is about fixing wrong settings in muxing,
> >>> pullup&pulldown and disabling voltage regulators when not in use or OMAP
> >>> is in retention.
> >> Just to confirm, these 18 days are already on N800 with OS2008 and with 
> >> those sw issues fixed?
> > 
> > I don't remember if i checked exactly the sw version that is public atm
> > but if it wasn't then it was close enough.
> > 
> I can't imagine those fixes are in the current software, or anything close to them as a few weeks ago I performed an idle run-down test on an N800 with 2.2007.50-2 (a freshly flashed device with no configuration changes whatsoever, so essentially a factory fresh install with a fully charged battery). After 12 days and 2 hours[1] the low battery alarm began to sound - that is just 2/3rds of what you are saying is possible so why such a large discrepancy - could my 9 month old N800 battery really have lost 1/3rd of it's capacity? Or can this difference really be down to component variance (the tested N800 is from March 2007)?

At the risk of sounding like a lawyer, if you check my original post, i
wrote _projected_

That means that over a short run (less than an hour), current is
measured (very accurately) and then applied to the battery capacity.

This test ensures that there are no obvious issues with high to medium
frequency. I am not aware of anybody here really measuring the battery
life over days. I used to do it in 770 times when the activity was a
little bit less hectic (and at that time the test was for only 11 days).

The fixes i mentioned are there, but there might be something else, at a
different level, which compromises the actual achieving of such high
idle times.

We don't use real batteries for he measurement, so that is out of hte
equation in our measurement and i really don't know what's the aging
profile of those batteries.

This is in general why the promised use time is shorter.

When the product is in conception/requirement definition phase, use
times for several use cases are defined and not always in a way that
really stretches the HW/SW capabilities.

So as long as a requirement is met, we are happy with it and move
forward to fix the next bug/issue.

With 770 the focus was on idle time, then with the first releases on
n800 it started moving to idle & connected and n810 has brought more in
the hot spot _active_ use time.


Cheers, Igor


Igor Stoppa
Next Generation Software
Nokia Devices R&D - Helsinki

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