[android-developers] Re: Extreme battery life

On Nov 22, 1:44 pm, Mark Murphy <mmur...@commonsware.com> wrote:

> If your CPU is in sleep mode except during a small window to gather
> and upload your data (e.g., using AlarmManager) maybe you could get
> this sort of life, but I'm dubious it can make it 4 months. After all,
> the battery loses power even if the device is completely *off*. If the
> CPU is supposed to be on all the time collecting sensor data,
> fuggedaboutit.
>
No, I don't have to take sensor data except right before I launch the
daily reading. But even when the CPU is just ticking over doing
nothing it still has to keep a bunch of volatile state in registers
and RAM and such. All that stuff might add up to over 1 mA. Really
deep sleep modes usually store everything volatile into flash and then
current drops to under 10 uA - just enough to run a little wake-up
counter. But I don't think Android can do anything like that, even if
the underlying hardware (like the ATMega) supports it.

Solar is not an option but outboard batteries might work. Charging
through the USB port is not very efficient, though, so I'd lose a lot
of the benefit of a big external battery.

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