This Instructables describes in detail how to build your own solar powered mobile phone.
Linear Technology article discussing solar charging, using maximum power tracking - see extracts
http://cds.linear.com/docs/LT%20Journal/LTMag-V19N4-04-LT3652-JimDrew.pdf
The idea dates back to 2002 when I was working on my dissertation on methods of energy scavenging that could be integrated on silicon. On a footnote, I added simple calculations demonstrating that if the surface area of a 'candy bar' mobile phone is covered with solar cell of 5% efficiency (which is pretty rudimentary), including a DC/DC converter, the overall output power is sufficient to augment the battery, providing power for stand-by indefinitely.
And here it is! Or rather a simplified version that is equally effective if not better!
Specifically what you need:
The Motorola F3 - a very cheap (I suspect the cheapest mobile phone there is) phone that is widely available both in US and UK. It is this affordability and basic ruggedness that I had chosen this model. More on this later...
A solar panel - the one I had acquired is available online (more on this later) but any other suitable make can be used provided it is rated 4.5V and above, having the dimension not larger than 100mm x 40mm.
A Schottky diode, 1N5817 or equivalent - a basic component which is not hard to find, you can even use the SMT version as long as you can solder some wires on both ends.
Some wires, I use enameled wire, more on this later...
Some basic soldering + a sharp pen knife + aluminium tape + epoxy + a hand drill + super glue
That's it! Surprised it is so easy? Why not get your hands dirty and build one!
The finish product is shown below.
Linear Technology article discussing solar charging, using maximum power tracking - see extracts
http://cds.linear.com/docs/LT%20Journal/LTMag-V19N4-04-LT3652-JimDrew.pdf
The idea dates back to 2002 when I was working on my dissertation on methods of energy scavenging that could be integrated on silicon. On a footnote, I added simple calculations demonstrating that if the surface area of a 'candy bar' mobile phone is covered with solar cell of 5% efficiency (which is pretty rudimentary), including a DC/DC converter, the overall output power is sufficient to augment the battery, providing power for stand-by indefinitely.
And here it is! Or rather a simplified version that is equally effective if not better!
Specifically what you need:
The Motorola F3 - a very cheap (I suspect the cheapest mobile phone there is) phone that is widely available both in US and UK. It is this affordability and basic ruggedness that I had chosen this model. More on this later...
A solar panel - the one I had acquired is available online (more on this later) but any other suitable make can be used provided it is rated 4.5V and above, having the dimension not larger than 100mm x 40mm.
A Schottky diode, 1N5817 or equivalent - a basic component which is not hard to find, you can even use the SMT version as long as you can solder some wires on both ends.
Some wires, I use enameled wire, more on this later...
Some basic soldering + a sharp pen knife + aluminium tape + epoxy + a hand drill + super glue
That's it! Surprised it is so easy? Why not get your hands dirty and build one!
The finish product is shown below.
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Signing UpStep 1: Introducing the solar powered phone.
So here's the phone, you can get one from Orange (UK network provider) with a pre-paid SIM card for a princely sum of �9.99! (no kidding! Stretch those credit crunched dollars!)
A sign of its popularity , the phone has its own Wikipedia page!
http://en.wikipedia.org/wiki/Motorola_FONE_F3
Some background on this model.
First off, it is VERY basic, you get more ring tones than functions on this phone, supposedly it was designed for developing countries, interestingly, it has an E-INK display that is very readable in bright sunlight and very good reception.
Turn-offs? SMS on this thing is atrocious! Bottom-line, the price far out-weights everything, if it is made of cardboard it would be disposable.
And here's the solar panel, I chance upon this little panel on an web-shop, www.dealextreme.com (I am not affiliated with the site)
see:
http://www.dealextreme.com/details.dx/sku.12988
The dimension is PERFECT. Fits the phone like peas in a pod.
I don't have any data on the stand-by power consumption, just an estimate based on the number of hours it takes to drain the battery (3.7V, 700mAh). It works out to about 22mW (Typical P = 6mA x 3.7V). Of course this figure jumps significantly to a watt when the phone is in used (as in transmitting). The idea is to provide power in excess of the stand-by power consumption to charge the battery. More on this later.
A sign of its popularity , the phone has its own Wikipedia page!
http://en.wikipedia.org/wiki/Motorola_FONE_F3
Some background on this model.
First off, it is VERY basic, you get more ring tones than functions on this phone, supposedly it was designed for developing countries, interestingly, it has an E-INK display that is very readable in bright sunlight and very good reception.
Turn-offs? SMS on this thing is atrocious! Bottom-line, the price far out-weights everything, if it is made of cardboard it would be disposable.
And here's the solar panel, I chance upon this little panel on an web-shop, www.dealextreme.com (I am not affiliated with the site)
see:
http://www.dealextreme.com/details.dx/sku.12988
The dimension is PERFECT. Fits the phone like peas in a pod.
I don't have any data on the stand-by power consumption, just an estimate based on the number of hours it takes to drain the battery (3.7V, 700mAh). It works out to about 22mW (Typical P = 6mA x 3.7V). Of course this figure jumps significantly to a watt when the phone is in used (as in transmitting). The idea is to provide power in excess of the stand-by power consumption to charge the battery. More on this later.
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If you have a digital multimeter, the diode measurement mode will tell you the forward bias voltage (when conducting), if not so simply set up a circuit, battery and a torch bulb, alternate the terminal of the thing you suspect is a diode, it should block one way.
What I have suggested about the choice of panel is in the instructables...
However your last question pique my interest, frankly I had abandon the phone for another, reason, it is very basic, the screen does not do text proper.
But since I did this, there are quite a number of phones with the new feature of augmented solar charging on the back of the phone, google, you will probably get a few hits.
(700mAh @ 3.7V) = 2,590mWh of battery available.
If the phone consumes 22mW continuously in one hour it will have consumed the equivilent of a 22mWh battery and in 117 hours it will have consumed the whole 2,590mWh battery....
According to the F3 spec... the phone is supposed to have 300 hours of standby time... not 117hrs.
What am I missing here?
Thanks!
I prefer to use my actual real life run-down test.
What am I missing here? :)
I do think you are missing something... Mobile phone transmmission power can vary depending on its distance from the base station, I am suggesting it could go up to a watt, as a typical maximum, assuming worst case, why would I want to rely on Motorola happy-clappy specification of 8.3 hr (if what u say is even true)?
I don't really need to know how their ideal figure is obtain, I know for sure it is not true or exact in real life.
I have a suggestion, why not you get one of these phone and test it out, IF you don't get that figure, please sue them for false advertisment, and then ask me to correct my instructables.
Is that alright?
http://www.instructables.com/id/37v-emergency-charger-Nokia-cellular-with-9v-batt/
First, over-charging, above the cell maximun floating voltage, typically at 4.2V, might shorten the battery life, destroying the battery in this case? No. I think you need a massive wallop of energy which the solar panel can't ever provide to edge it pass thermal runaway. But note that the Li-ion cell can also self-discharge, and the phone does consume minute standby power, obvious to the fact that it maintains the time and date after you had switch it off.
Second, if you're thinking of using a zener with a breakdown voltage of 4.2V, it is not necessary a good idea, 1)Zener diode reference isn't accurate enough (+/-5%?) 2)Exact value to what you have in mind may not be readily available, or even if there one, I would advise, something nominally derated minus 5%.
I had advise against this (overcharging). I reiterate, in circumstances as such that your mobile phone battery is fully charged, you turn it off, leave it under the sun charging. Do not such thing with this simple circuit.
To find out more about Li-ion battery, I recommend an excellent article from Linear Technology quarterly magazine on the charging and discharging method that extends Li-ion battery life.
http://www.linear.com/ltmagazine/LTMag_V18N3_Sep08.pdf
I followed the link to the Wikipedia Web page for this phone, and it said that this is CDMA, didn't they get rid of that in like May? Or is this only in Australia? I got a phone that I found at some garage sale for 10c with charger and instructions so I bought it, to find that I couldn't ring out, send or recieve text because it was CDMA. Now I would really like to make this and it sounds great, but that 1 small thing is quite ominous as a could be failure. D =
Reards,
Kryptonite