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Author Topic: why doesn't the back of every mobile phone have a solar panel?  (Read 4063 times)
MR GUS
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« on: May 23, 2008, 10:25:25 AM »

ok, they may be small but since 2002 haven't really got any smaller.
So why doesn't each phone have a basic nigh on full sized rear thats a sturdy small basic solar panel to simply turn the thing over & grab what's free in order to top up from light either on the bus, outside on a window-sill etc, after all we all have vibration & rings turned to max.
 How much would a few hours a day add to a mobiles standby? taking an item such as the freeloaders panel (1 of 2) as a starting point for design.

no effort for people who don't like to think!? as we all leave em on desks etc 1/2 the time
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Austroflamm stove & lot's of Lowe alpine fleeces, A "finger" of Solar Sad
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Joules
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« Reply #1 on: May 23, 2008, 11:00:12 AM »

I estimate with todays PV panels the size of a mobile phone would take 3 weeks to charge the internal Li-po assuming it was pointing vaguely at the sun.  You could wear your mobile on your head or shoulder. Be much better to have a home/office/car solar charger that can soak sun (when it's visible) and rapid charge the phone.... A bit like a better built free-loader.  I know, as I currently have a Solio, and whilst it charges a PDA, it then takes   nearly a week to recharge itself on the window sill.

                                          Joules
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RichardKB
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« Reply #2 on: May 23, 2008, 05:23:00 PM »

Because PV panels do not work in your pocket.

Rich
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MR GUS
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« Reply #3 on: May 23, 2008, 05:30:14 PM »

I must be a freak then as mines always in my hand for some reason, failing that by the window, hate scratching it with keys in pockets.

think i'll try lugging my freeloader about & experiment
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Austroflamm stove & lot's of Lowe alpine fleeces, A "finger" of Solar Sad
Noli Timere Messorem
Screw FITS ..it is, & always has been about the environment (said the penny-pinching Scotsman)
RichardKB
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« Reply #4 on: May 23, 2008, 05:55:40 PM »

 Cheesy I very rarely carry keys in my pocket. Left front pocket only has mobile in never anything else.

Plus as joules said the charge time would at best putback the mains charge a bit.

Rich
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Ivan
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« Reply #5 on: May 24, 2008, 12:10:16 AM »

It would be really useful when camping, or when ship-wrecked, or at festivals. Even if you had to leave it in the sun for a few hours, to get a few minutes phone calls - it might serve a useful emergency backup.
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MR GUS
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« Reply #6 on: May 24, 2008, 02:54:52 PM »

yes, it would be nice to have the option of thin flip out panels (if you don't need the smallest slimmest phone available) ..a built in 3 panel charger like the solio would be the sort of phone i'd happily invest in when upgrading) ..what with the processing power of the phones these days it would be nice to know what sort of pull it was able to attain via the screen so you could work out what sort of light opportunities you'd need to attain part or full charges, could potentially shut up solar dissenters.
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Austroflamm stove & lot's of Lowe alpine fleeces, A "finger" of Solar Sad
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Screw FITS ..it is, & always has been about the environment (said the penny-pinching Scotsman)
KenB
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« Reply #7 on: May 25, 2008, 09:05:32 AM »

List,

One of my chargers is rated at 4.2V, 800mA or 3.36W.  From my experiments with solar garden lights, I have seen 4.2V, 25mA in very bright sunlight from a 50mm square pV. Multiplying this up would need an area of 400 x 200 mm to provide a similar charge. My 10W pV was about 300mm x 300mm IIRC.

It would probably be better to carry a second battery with you, if you are thinking of getting caught short.

If manufacturers could only standardise on a common size and capacity for a Li-Po battery, and design phones, cameras, MP3 players etc around the standard, you would then be able to purchase them anywhere (garages, chemists, post offices, supermarkets).  You might also be able to buy a cheaper non-rechargeable alkaline version, that would keep you going for an hour or so.

Batteries, however, are an expensive and very planet unfriendly way of buying electricity.

There have been various offerings of hand cranked and foot operated generators.  The foot operated on is like a car foot-pump in action, where each downward stroke spins up a flywheel that is geared up to run a small dc generator.

Most Li-ion phone and camera batteries are 3.7V and 600 to 1200mAh  (2.25 to 4.5Wh)  - so 15 minutes of pumping on a foot generator could give a boost to these.



Ken
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Ivan
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« Reply #8 on: May 25, 2008, 04:05:40 PM »

Just checked the battery in my phone - 3.6v, 900mAh. So it stores 3.6v x 0.9Ah x 3600sec = 11664Joules of energy

Ken's solar-powered light gives 25mA at 4.2v, which over an hour, yields 4.2v x 0.025 x 3600 = 378 J

So you'll need 30hours rated output from Ken's panel to recharge the battery. ie 30hours bright sunshine, assuming no losses in the system.
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