[Gta04-owner] How could GTA04 shine

[thomasg]

On Thu, Mar 8, 2012 at 23:42, Bob Ham <rah at bash.sh> wrote:
> On Thu, 2012-03-08 at 12:37 +0100, thomasg wrote:
>
>> I don't think the price is really the matter here. The problem is,
>> that there are no panels which are so efficient that this small
>> surface will be good for anything.
>
> I don't believe that is necessarily the case.
>
>> Also, the peak performance is really hard to reach, as you say
>> correctly, it has to be sunny, you have to point the device in the
>> right direction (and angle!), it can't be too hot (the efficiency at
>> above 320K temperature will be reduced), so all in all even in good
>> conditions you're likely not exceed 70% of the peak performance.
>
> There is a panel here
>
> http://uk.farnell.com/bp-solar/msx-005f/solar-panel-0-5w/dp/654000
>
> which is rated at 500mW; 150mA at 3.3V if I understand the
> specifications correctly.  Seventy percent of this is 350mW which is
> significant.  In fact, it's exactly the power used by the USB
> trickle-charge; 70mA at 5V = 350mW.
>
> This particular panel fits the length of the openmoko case but requires
> slightly more width and would need squared corners.  Of course, having
> the design files for 3D-printable cases one is not limited by the
> existing backplate dimensions or shape :-)

You're right, the specs are a lot better, but it can't be made fit in
the already bulky Neo casing (although it would fit into cases of
modern phones with 4.5" screens).
Also, it is important, that this panel generates a very low voltage.
The nominal voltage under testing condition (which includes cooling
the panel down to 298K ) is only 3V. In mediate climates under full
sun, you easily get 320K or even more panel temperature, in this case
the voltage will drop rapidly and I don't believe that you can
actually charge a LiIon battery with under 2V.
Not to mention, even with 500 mW max. at optimized testing conditions,
it is unlikely that you will get out more than 350 (or rather 300) mW
in real life.

Again, I don't think this can be really valuable, even in theory, not
taking into account that you have to get this thing in and protected
for every-day use.

> --
> Bob Ham <rah at bash.sh>
>
> for (;;) { ++pancakes; }
>
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