I found a guide online that shows how to make a solar phone charger (in a bottle), and I thought I'd try it out, but I'm worried about damaging my iPhone 4 (for a school project).

(If anyone's interested, it's found here: http://www.instructables.com/id/Solar-7-up-Solar-phone-charger-in-a-bottle/#intro)

But basically you use small pieces of solar cells (the author of the guide calls them "solettes") and superglue them together in series (so it's not exactly a solar panel; it does what you need though). 11 solettes are needed.

I purchased them on eBay as 52x19mm solar cells; the seller gave the following information for each:

Average Power (Watts): 0.14 Wp

Average Current (Amps): 0.28 Imax

Average Voltage (Volts): 0.5 Vmax

Effeciency: 17.6%

Everywhere I looked said iPhones need 5V since it uses a USB charger, so as the guide says, you'd need ten 0.5V solettes, plus one " 'false' solette that doesn't produce electricity but just serves to bring do the top surface connections to a solette underbelly". To my understanding, amps and watts don't really matter, the volts do (I think higher amps/watts just mean it would charge faster)? I'm really new to all of this.

Anyway, the voltage will probably differ a bit from the required 5V and also the amount of sunshine you'd get would change things a lot, so I was wondering if getting the wrong amount of voltage (and oftentimes - when the sun isn't shining - less voltage) could damage my phone.

A lithium battery and a lithium charge chip or board is also needed. The author used a 2000mAh LiPo. The guide says:

In order to power the LiPo charge circuit, which then pumps current into the LiPo battery, which then charges your smartphone, we need to produce 4.8V - 6VDC from our homemade solar panel.

I was wondering if it was possible for someone to explain this part a bit. The cheapest rechargeable 2000mAh LiPo battery on eBay is a 3.7V one (others have 11.1V, others have 7.4V, etc). Can I use any kind of battery? And what I don't understand is if the battery has its own voltage then isn't the amount of volts that goes to the phone 3.7V (from the battery) rather than 5V (from the solar panel)? I'm sorry if this is a stupid question, even a link or something would be sufficient, I couldn't find an explanation online myself.


closed as off-topic by Fizz, PeterJ, Null, Daniel Grillo, Nick Alexeev Oct 2 '15 at 18:41

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Fizz, PeterJ, Null, Daniel Grillo, Nick Alexeev
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ This whole question could have been cut down to the last paragraph. \$\endgroup\$ – Fizz Oct 2 '15 at 2:36

The LiPo charger used is a LiPro Rider Pro, that charges the LiPo from the solar panel (or usb) using a LiPo charging regulator and also steps up the voltage from the battery to 5v for usb out, using a switching boost regulator. See Seeed's wiki page for the charger for more details.

  • \$\begingroup\$ I honestly read that page over 5 times and also the page for the original LiPo Rider, and I'm still not sure, so I'm asking; so basically if I bought this LiPo Rider Pro, can I use any kind of LiPo battery? e.g. this one, that is described as Capacity: 2600mAh Cells:4S Volts : 14.8V Continuous discharge rate : 40C Max discharge rate : 80C Max charging rate : 10C". It's for a dollar: ebay.ca/itm/… \$\endgroup\$ – Seven Mar 14 '13 at 21:23
  • \$\begingroup\$ @seven Absolutely not. The lipo charger regulator on the LiPro Rider Pro has a 6.5v absolute maximum. It's normally 4.6 to 6v input. It would not be able to charge a 14.8v lipo pack. It is intended for a single cell 3.7v lipo. Notice that 7.4, 11.1 and 14.8 are all multiples of 3.7? You would need a 14.8v lipo charger for that. \$\endgroup\$ – Passerby Mar 15 '13 at 3:19
  • \$\begingroup\$ Apparently its minimum is 4.8v; so wouldn't that mean a 3.7v LiPo is not okay? (Since it's under 4.8v....?) And I don't really understand how this guy hooked up the battery and the LiPo Rider Pro, but I'm guessing that the solar panel is charging the battery which then charges the iPhone (via the USB)? So then at night, if the the battery wasn't all used up during the day to charge the phone, would the solar charger still be able to charge the phone? So the solar phone charger is basically a solar battery charger? \$\endgroup\$ – Seven Mar 15 '13 at 21:29
  • \$\begingroup\$ 4.8v is the input voltage to the charger circuit. \$\endgroup\$ – Passerby Mar 15 '13 at 22:25

Not the answer you're looking for? Browse other questions tagged or ask your own question.