Why don't cell phones make use of solar power to help charge the battery?

[dracoi]

Maybe they won’t wear it on their heads, but they just might wear the solar panels on their shoulders: Solar Powered Jacket from SCOTTeVEST

[constanze]

@MyFootsZZZ

Really!? The person that asked me seemed to take some pride in thinking up the idea. I guess he was beaten to it.

Only about ten years or so.

[constanze]

@filmore

Solar cells don’t provide much charge. Devices like the iPad want a 1amp charger, which is a lot. So even if they had cells, it might be like trying to fill a bucket with an eye dropper.

I don’t know about the iPad, but normal cell phones aren’t a problem, because the solar cells charge the Akku (US battery), and the cell phone uses the battery.

[constanze]

@Hampshire

Cost wouldn’t be a factor since you can buy solar calcualtors for $3 now. Space wouldn’t be a factor either since they could be built into the frame of an ipad under the glass.
I’d guess you just can’t draw enough power from a small solar cell to make it worth it.

Calculators don’t need batteries, they run directly from the solar cell.

Cell phones, on the other hand, use an Akku anyway, so charging it with solar cell instead works just as well.

The model that PEARL sells is specificially no-frills - no phones or 100 different functions, just phone, flashlight, radio and “a few games”, but also waterproof, can be dropped and lasts 100 hours. In other words, targeted towards the outdoor market of people who hike through desert/ mountains/ jungles and can’t charge by plugging into an outlet.

The other big benefit of the generic charger (PDF) with a dozen assorted plugs to fit into every different cell phone is 3rd world. Cell phones are already used to bridge the gap of no land lines; now 3rd world groups are donating universal chargers (with a flashlight) and different plugs. People offer to charge cell phones for a few cents, and everybody is happy.

[constanze]

@Reply

Now that doesn’t sound so bad (half an hour to full charge under ideal conditions), but 1 square foot is a huge PV charger for daily use. How and when would you carry that on your person? The “typical” pocket charger (like Solios), last time I checked, put out no more than about 1 watt. That means that in perfect conditions, a pocket charger would take 5 hours to charge your cell phone.

And why does that matter, if normal charging time when you plug the phone into the power outlet is also usually around 4-5 hours? The formula is not “The more power to charge with, the faster it goes”, but rather "in order to make the Akku (US battery) last longer, it needs to be fed a specific charge at a specific pace, and the charger will either step it up (from solar) or down (from household currency). (That’s also why the charging bricks get so warm: they step the power down.

They do sell big portable, foldable panels for more generating capacity for extending camping trips, but the idea is that you’d leave it at camp and let your electronics (or a battery pack) sit there and charge for a long time.

Or you let it hang outside your office window/ car window while the phone is inside.

In other words, you just need a lot more square footage than most people are willing to lug around daily. (The technology is improving and there’s a lot on the horizon, but not yet accessible to the mass market)

Except that there are quite a number of solar chargers already out there which are roughly the same size as the cell phones or a bar of chocolate, for ease of transport.

The new market are the wearable soft panels, that you slot (as others have mentioned) into your jacket or onto your backpack.

2. It’s really hard to get maximum exposure. Depending on the particular PV technology used, even partial shade can substantially decrease power output. I’m talking clouds in the sky, your head (if you’re wearing it), overhead trees, mountains, being indoors through a window, etc. all decrease your PV charger’s effectiveness, and when you only have 1W max capacity to start with, you don’t have a lot of wiggle room.

You make it sound as if a bit of clouds means doom. It doesn’t. Even with a cloudy sky, you have 70% UV exposure for example. Most of the US is very far south anyway and gets plenty of sunlight. Clouds just mean that instead of 5 hours, it takes 7 hours to fully charge.
And the chargers do have cords. It’s quite possible to put them on a ledge or windowsill outside the window and lead the cord back in where the phone is resting.

3. People like to use their devices during the day and charge at night, which is of course counter to what the sun does. Some manufacturers work around this by including a battery pack in the charger, charging that during the day, and using that to charge your device at night.

Is that your personal observation or a general study in usage habits?

4. Even the cheap chargers are like $60+, and for shorter trips it often just makes more sense to buy an additional battery, pre-charge that and bring it with you. Much simpler, much more reliable.

Um, what kind of cell phone are you using? All the ones I know of have inbuilt Akkus (batteries) that can’t be swapped out like two Mignon batteries (Because they eat so much they need NiMH or LiOn Akkus). That’s why “emergency chargers” are being sold - not for the people lost in the wilderness, but for people in the city stranded away from the next electric outlet expecting an urgent call.

If you don’t have the option of swapping the Akku, or if the Akku isn’t sold seperatly (I haven’t seen one yet, because of the short life cycle of cell phones in general), then being able to charge it whenever the sun shines without needing access to an outlet can be quite valuable.

5. As for stationary indoor use, having a large-area PV charger just to charge your phone probably doesn’t make sense on either a financial level (electricity doesn’t cost that much when you have access to it) or a life-cycle analysis, energy-payback level (will the energy spent in manufacturing and distributing the charger ever get paid back through its expected use?). I haven’t done the math to make sure, but that’s what I suspect…

Ah, the utopia fallacy combined with the double standard: solar panels are condemned because it takes energy to produce them, but the other forms of producing electricty are given a pass on manufacturing cost; and because it’s not perfect or cheap yet, it’s better to keep using the bad technology instead of switching.