So, as my fellow iPhone 3G users will know, the battery life is not really sufficient to last through the day when the device replaces a cellphone, an iPod and a portable gaming console. Special battery packs exist, but they are quite expensive and make the device a lot bigger so it would no fit into a iPhone case any more.
The Chinese Internet store Deal Extreme sells a 2000mAh battery that recharges itself using the built-in solar panel for less than 11,50€ including shipping. That would be enough for recharging the iPhone completely. I ordered it to play around with it a little bit. By the way, if lugging around the whole power plant seems strange, you could use a 2xAA emergency USB socket (like this one) and recharge the batteries at home using a solar battery charger (like this one).
The battery looks quite good, it it roughly the same size as the iPhone and surprisingly light. It has two LEDs, a green one thats shows how much the battery is reloading (the brighter the day, the brighter the LED) and a red one that glows as soon the included 30cm pigtail with a USB-A socket on the other end is connected to the strange proprietary socket on the battery. The pigtail is a bit long for my application, but OK, you can’t have all at once.
After removing the panel, you see a very nicely done circuit board and an unlabled Li-Ion battery that might actually have the capacity that is advertised. If 2Ah isn’t enough, there’s plenty of room to add another battery, giving the whole thing 4Ah.
Connecting a stupid USB LED light, it works, but the iPhone 3G doesn’t start charging when I plug a retractable 1€ iPod sync cable into the pigtail. I read somewhere that the iPhone had to be told to recharge by the iPod helper software (It also doesn’t recharge if you plug it into a Linux box), so only feeding it 5V won’t do the trick. On an iPod pinout page, I found a description stating that I had to pull D- to 5V and D+ to GND, but that also didn’t work. Time for measuring the original Apple USB charger, which certainly doesn’t run iTunes and puts out 2.8V on D- and 2.0V on D+, but there’s no way I could put 4 different resistors into the iPod plug to feed it both these currents.
But 2.5V, which is what I get when I cut USBs 5V in halves with two 200k resistors (12uA leak current…), might be close enough. Tried it and it works, the iPhone charges. Great!
For Jeff commenting below, I included the best pic I have (my camera sucks big time). Just remove the two data cables, take the 2 resistors and solder them together as closely as possible. Cut one of the legs without resistor and bow the other around, giving an M shape. Cut all three wires to have the same lenght. Solder the two legs with resistors to the two pins that have the power cables and the other leg to both the now free pins. They are quite close to each other, so you can bend them together. Btw, the resistors were produced in the GDR circa 1970, funny they now are used to charge capitalistic high tech equipment.
The whole setup will be so small that you can still put the plug back into the original casing, I had to label the new cable so I do not mix it up with the other ones and wonder why it doesn’t sync:
I tried hacking together a schematic with OpenOffice.org, but this was an utter failure. 😉
Projects by deBaer 