[Gta04-owner] How could GTA04 shine

Christoph Mair christoph.mair at gmail.com
Thu Mar 8 10:05:46 CET 2012

On Thu, Mar 8, 2012 at 9:43 AM, Bob Ham <rah at bash.sh> wrote:
> On Thu, 2012-03-01 at 19:27 +0000, Radek Polak wrote:
>> while we are talking about competing with Android and iPhones, here is my idea
>> that can make GTA04 attractive:
>> - solar charging - not many phones have this and it should be quite easy to
>> place small solar panels on the back of GTA04. And they are quite cheap...
> I think this is an amazing idea.  Now that we have viable 3D printable
> case designs, this is a realistic possibility.  It would be easy to
> design a new, thicker backplate that can house a solar panel.  I can
> imagine having one unmodified backplate for normal usage and one
> backplate with a solar panel to take to music festivals, camping, etc.
> A quick bit of searching turned up this suitably-sized panel
> http://uk.farnell.com/sanyo/am-5710car-sce/solar-cell-outdoor/dp/1679078
> which is rated at 134mW.  I presume the electrical output would have to
> be conditioned somehow before being fed to the battery controller.  Do
> any of the EE-minded people here have an idea of what that would entail?

The open circuit voltage is specified with 6V. The AC charge path
(available at the debug connector) supports 6.5V maximum. Therefore It
should "just work" to connect it directly to these pins. To get better
efficiency a MPPT (maximum power point tracker) is recommended. Its a
chip which regulates its own input voltage to the value where the
panel delivers the highest output current.

Just one note: the highest current you can get from this solar panel
is 15mA. Unfortunately we (still) do consume a lot more power during
suspend. This solution will only charge the battery (very slowly!)
when the device is off. But the Idea is great anyways. Maybe there are
other (foldable?) panels with higher output power..


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