At 2:41 PM -0700 10/17/99, [EMAIL PROTECTED] wrote:
>Do the newer Power Books really use so little power and have such excellent
>power management that they can get up to 6 hours on a single battery, or is it
>the batteries themselves (or even some combination of the two would work for
>this question)?
Mostly better batteries. The energy density of a modern LiIon
battery is very high compared to older batteries.
Also, I believe it's only the iBook (which has a rather large battery
and a smaller screen) which is supposed to get 6 hrs on 1 battery.
The bronze PowerBook G3 is supposed to get about 4 hours per battery,
and I've heard that's not too far from the truth if you turn all the
power saving features on.
>If the computer can't take advantage of the superior batteries, because it
>doesn't "know how", then why not a software solution that monitors the power
>management firmware and intercedes on behalf of the new battery, much the same
>way the 2400's G3 upgrade L2 cache card works, by telling the logic board CPU
>to ignore the startup process and taking control itself.
That isn't how it works at all. There is no CPU on the logic board
in the 2400. The G3 upgrade completely replaces the original 603e
and the original L2 cache. Since the 2400's firmware doesn't know
how to activate the G3 cache, you have to run a system extension or
control panel which turns it on partway through the boot process.
> I mean if software
>can control battery reconditioning and monitor battery life, why not control
>power management?
Because software can't actually control battery charging directly.
Apple (and everybody else for that matter) designs their notebook
power controllers to be mostly independent of the main CPU. In
Apple's case, the PMU chip controls the entire power system.
Programs which "recondition" batteries really just suppress the
ordinary MacOS automatic low-battery shutdown so the battery can
fully discharge. MacOS itself is told by the PMU when the end of the
battery is imminent. (Once the PMU thinks the battery is really
dangerously low, it will just shut down the machine without even
asking the OS.) Similarly, monitoring battery life is a matter of
asking the PMU how much life it thinks the battery has left.
The PMU is an independent 8-bit microprocessor with its own control
program. If you could change the control program, you might have a
chance at safely charging newer battery types. Unfortunately that
control program is stored in read-only memory burned into the PMU
chip itself, so there just isn't any way to change it.
Besides that, the Duos probably do not have the charging hardware to
support current battery technology. Lithium ion is quite different
from the NiCd and NiMH batteries the Duos used. All rechargable
battery technologies require constant monitoring throughout the
charge process to determine when to stop charging. NiCd and NiMH
only need voltage monitoring. Lithium ion also requires monitoring
of current, and requires that the charger be capable of switching
from voltage- to current-controlled charging. Without these
capabilities, there is no way to safely charge a LiIon battery. And
the risk of unsafely charging one is an almost certain explosion,
meltdown, or fire caused when the battery overheats.
Tim Seufert
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