Tech Forum

First, under load shouldn't be that much different from being off as long as the circuit can handle the current needed to do both jobs. That you will need to measure and then find a pre-built circuit to do the trick.

I suggest pre-built since they are so cheap. I did the same kind of thing for a phone that refused to recognize its own charger as a valid charger. A good ol' Motorola phone, I'll never buy another phone that has some type of recognition routine in it to check the charger.

In any event, the first thing I noticed was that my camera charger was for the same type of battery, same voltage, same AHr rating, same Li Ion battery. I hooked up wires from the charger into the phone and it worked just fine.

Next I wanted a more universal Li-Ion battery charger & found more than one on-line. The one I settled on was from dx.com:

1A Lithium Battery Charging Module - Blue  $1.70/e
[url=http://dx.com/p/1a-lithium-battery-charging-module-blue-205188]http://dx.com/p/1a-lithium-battery-charging-module-blue-205188[/url]

There are others as well, a Red at 3A for under $9
[url=http://dx.com/p/1a-lithium-battery-charging-module-red-318740]http://dx.com/p/1a-lithium-battery-charging-module-red-318740[/url]

These are circuit cards usually with a USB power port to give it 5V 1A to work with, so you will need to do some soldering for connections to the battery from the board.

At 1A, expect to charge and run your phone without a problem, since most cell phones, even on transmit, are below 1W output. see: [url=https://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health]https://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health[/url]
and
[url=http://hypertextbook.com/facts/2006/EbruBek.shtml]http://hypertextbook.com/facts/2006/EbruBek.shtml[/url]

Charging your iPhone should not require any special accomodations. The OEM charger from Apple supplies 5V at 1A via a USB connection with proper cable. Either the 30 pin connector or the new 5 pin "lightning" connector cable both deliver the same power.

The phone (as all phones now) has built in current limiting, temperature sensing and voltage sensing to protect the battery.

You just need to deliever 5V, regulated, to the cable with, of course, polarity protection for the solar charger. A simple LM7805 regulator IC is what most chargers use for the 5V.

It really is NOT a good practice to leave the phone on the charger continually, as most rechargable batteries 'like' to be excercised. Charge it up, let it run off battery until it shows recharge is needed then reconnect charger. You should get several years of service from it.