After I posted my last article I decided to do some experimenting based on the description of the DIY iPhone 3G charger I linked to.
I checked the two travel chargers I have, and just as expected: The one that charges the iPhone 3G has a 2.4v and 2.8v reference voltage applied on the data pins in addition to the 5v charging voltage. The one that charge my iPod but not my iPhone have no voltage on the data pins.
So, I guess the solution is to make a small adapter that gives the required voltage on the data pins: USB in, some resistors and USB out. Like described in the article about the DIY iPhone 3G charger.
That simple adapter will solve the problem of some of the USB chargers that won’t work on the iPhone 3G, but not the problem with the equipment that use the old FireWire method of charging (like the Dension ICElink in my car). For that you need a slightly more advanced adapter.
OK. So Apple ditched support for FireWire charging on the iPhone 3G. Stopping it from working properly with a lot of audio systems and car installations. FireWire support has been on its way out on the iPods for a long time and I guess Apple had to remove this feature at some point. Apple have a history of removing old technology pretty fast, but usually they have provided some kind of replacement. An external floppy drive when that was removed. An external DVD drive for the MacBook Air etc.
In this case they did not provide any adapters, leaving a lot of people pretty angry. Whatever. Other companies are already working on the appropriate pieces of electronics. And I need one of those, because the iPhone 3G will not charge in my car.
However, I am experiencing problems charging my iPhone through a lot of standard USB equipment as well. Stuff that charges my Nokia Phone, my iPod and a lot of other USB based gadgets.
It seems like the iPhone 3G does more checking on the USB port before it starts charging. Here are some examples.
The image shows two standard USB charging units. Simple connectors that converts the 12V in the car to 5V in the USB port. The white one charges my 60GB iPod but not my iPhone 3G. The black one charges both my iPod and the iPhone 3G.
The same goes for these travel chargers. The one to the left only charges my iPod. The one to the right charges both.
And because of the not-so-impressive battery life of the iPhone 3G it would have been nice if this portable battery / solar charger would work. But it won’t. Works fine on all USB based gadgets I’ve tried, but not on the iPhone 3G.
Others are also looking into this, but if you have a simple explanation or know about an adaptor that will make all USB chargers work on the iPhone 3G – please let me know.
I did some more research and found a solution.