PMU questions

PMU questions

[Colin Leroy]

Hi everyone,

I'm at a loss with a PMU-related problem... Basically something happened
and my iBook (G4 14") battery now thinks it can last only 30 minutes.
It used to be 3+ hours. I don't really know what happened.

After having tried to recalibrate it using Apple's secret-code
(shift-control-option-power) and cycling it, things only got worse. I
suspect it's due to the fact Linux doesn't put the laptop to sleep
when the battery empties, but I don't have an OS X partition nor can
backup 40GB...
So I'm about to buy a new battery, but I fear the stupidity of the PMU
will make it work as bad as the current one. So, here are the questions
I have, I think people there will be more apt to answer me than any
hotliner I could get at Apple:
- is the max_charge field displayed in /proc/pmu/battery_0 stored in the
PMU itself, or in the battery ? If I get a new battery and can't
calibrate it, I do hope it's stored in the battery, but I'm really not
sure about that.
- Would there be any way to overwrite this value by using some hack in
via-pmu.c, or is that PMU a real black-box ? If it's writable, does
there exist code somewhere to do that, or some doc I could use to write
it ?
- If there are people on this list with an iBook g4 14", could you tell
me what's your max_charge value is ? mine is now 507... :-/

Many thanks in advance...
-- 
Colin

Re: PMU questions

[Benjamin Herrenschmidt]

On Tue, 2004-10-19 at 07:20, Colin Leroy wrote:
> Hi everyone,
> 
> I'm at a loss with a PMU-related problem... Basically something happened
> and my iBook (G4 14") battery now thinks it can last only 30 minutes.
> It used to be 3+ hours. I don't really know what happened.

Happens all the time on Apple laptops lately. My tipb battery is now
half of it's capacity. Browse the archives on the web, you'll see that
it's a common disease with those.

> After having tried to recalibrate it using Apple's secret-code
> (shift-control-option-power) and cycling it, things only got worse. I
> suspect it's due to the fact Linux doesn't put the laptop to sleep
> when the battery empties, but I don't have an OS X partition nor can
> backup 40GB...

No, it has nothing to do with Linux. 

> So I'm about to buy a new battery, but I fear the stupidity of the PMU
> will make it work as bad as the current one. So, here are the questions
> I have, I think people there will be more apt to answer me than any
> hotliner I could get at Apple:
> - is the max_charge field displayed in /proc/pmu/battery_0 stored in the
> PMU itself, or in the battery ? If I get a new battery and can't
> calibrate it, I do hope it's stored in the battery, but I'm really not
> sure about that.

It's all coming from the battery itself.

> - Would there be any way to overwrite this value by using some hack in
> via-pmu.c, or is that PMU a real black-box ? If it's writable, does
> there exist code somewhere to do that, or some doc I could use to write
> it ?

Not that I know of.

> - If there are people on this list with an iBook g4 14", could you tell
> me what's your max_charge value is ? mine is now 507... :-/

You can try the following: disable pmud & pbbuttonsd, and let the machine
on & drain the battery until it shuts down by itself (empty battery). Do
_not_ let it go to sleep or whatever pmud does when it thinks your battery
is closed to exhausted. Drain the battery completely.

Then, do a full charge, and drain it again completely.

Do that a few times. If that doesn't help, then I'm afraid you have to
ask apple for a replacement battery.

Ben.

Re: PMU questions

[Colin Leroy]

On 19 Oct 2004 at 09h10, Benjamin Herrenschmidt wrote:

Hi Ben, 

thanks for your answer!

> Happens all the time on Apple laptops lately. My tipb battery is now
> half of it's capacity. Browse the archives on the web, you'll see that
> it's a common disease with those.

Ah, nice ("nice") to know... It looks like the more these batteries are
"smart", the faster they get fucked up...

> You can try the following: disable pmud & pbbuttonsd, and let the
> machine on & drain the battery until it shuts down by itself (empty
> battery). Do_not_ let it go to sleep or whatever pmud does when it
> thinks your battery is closed to exhausted. Drain the battery
> completely.

You mean until the laptop shuts down by itself ?

> Then, do a full charge, and drain it again completely. 
> Do that a few times. 

Without resetting the PMU ?

> If that doesn't help, then I'm afraid you have to
> ask apple for a replacement battery.

Yes, I think I'll do this. For the record, I found compatible batteries
a little less pricey than Apple's ones here:
http://store.craytonelectronics.com/apibba2.html  

-- 
Colin

Re: PMU questions

[Benjamin Herrenschmidt]

On Tue, 2004-10-19 at 16:34, Colin Leroy wrote:

> You mean until the laptop shuts down by itself ?

Yes

> > Then, do a full charge, and drain it again completely. 
> > Do that a few times. 
> 
> Without resetting the PMU ?

Yes

> > If that doesn't help, then I'm afraid you have to
> > ask apple for a replacement battery.
> 
> Yes, I think I'll do this. For the record, I found compatible batteries
> a little less pricey than Apple's ones here:
> http://store.craytonelectronics.com/apibba2.html  
-- 
Benjamin Herrenschmidt <benh@kernel.crashing.org>

Re: PMU questions

[Colin Leroy]

On 19 Oct 2004 at 16h10, Benjamin Herrenschmidt wrote:

Hi Ben, 

> > > Then, do a full charge, and drain it again completely. 
> > > Do that a few times. 
> > 
> > Without resetting the PMU ?
> 
> Yes

Thanks for your advice, it works a bit. I started with a
max_charge : 597

After the first charge/drain it went up to 
max_charge : 1854

Strangely enough after a second cycle it's now
max_charge : 1573

I can't find a logic in this stuff... Do you think there's a special
reason why Apple uses such a complicated method instead of 
a) charging until voltage stays equals for a few minutes
b) draining until voltage goes under 13.5 volts (or 13, or whatever)

In my uninformed opinion that would work better, wouldn't it?

-- 
Colin

Re: PMU questions

[Benjamin Herrenschmidt]

On Wed, 2004-10-20 at 17:46, Colin Leroy wrote:

> I can't find a logic in this stuff... Do you think there's a special
> reason why Apple uses such a complicated method instead of 
> a) charging until voltage stays equals for a few minutes
> b) draining until voltage goes under 13.5 volts (or 13, or whatever)
> 
> In my uninformed opinion that would work better, wouldn't it?

I don't know...

Ben.

Re: PMU questions

[John Steele Scott]

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> I can't find a logic in this stuff... Do you think there's a special
> reason why Apple uses such a complicated method instead of
> a) charging until voltage stays equals for a few minutes
> b) draining until voltage goes under 13.5 volts (or 13, or whatever)
>
> In my uninformed opinion that would work better, wouldn't it?

My opinion is only slightly more informed than yours, but I do know that the 
characteristics of modern rechargable batteries (lithium-ion or similar) are 
quite complicated . . . for instance even the method of charging them 
requires special controlling circuitry.

cheers,

John

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Re: PMU questions

[Jon Masters]

On Tue, 19 Oct 2004 09:49:40 +1000, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> On Tue, 2004-10-19 at 07:20, Colin Leroy wrote:
> > Hi everyone,
> >
> > I'm at a loss with a PMU-related problem... Basically something happened
> > and my iBook (G4 14") battery now thinks it can last only 30 minutes.
> > It used to be 3+ hours. I don't really know what happened.
> 
> Happens all the time on Apple laptops lately. My tipb battery is now
> half of it's capacity. Browse the archives on the web, you'll see that
> it's a common disease with those.

I took my 667 G4 Powerbook back to the John Lewis retail outlet where
I purchased it two years previously and they replaced the case
(scratched paintwork), battery (didn't last very long by now), the
right hinge (just in case), the DVD/CDRW drive, didn't reinstall the
software as per my request, and a bunch of other fixes.

Essentially it's nearly new at this point and I love it. The motto of
the story is that, in the UK at least, John Lewis -
http://www.johnlewis.com/ - are the place to buy Powerbooks. They're
cheaper than Apple, give a two year warrenty and twice now have
entertained my crazy notions of things they might want to offer me
under warrenty. The other thing they did was accept a return when the
first unit developed a single faulty pixel on the day I bought it -
not Apple standard practice either.

I'm currently thinking about getting another battery from one of those
online refurb suppliers, but am completely discharging this one as
part of each charge/discharge cycle. Over 4 hours of battery now with
the display set on full and while doing compiles, etc.

Jon.