A huge swath of accessories that were compatible with the first-generation are not compatible with the iPhone 3G, either failing to charge the device or losing functionality completely.
iPhone Atlas reader Carson's case is exemplary:
"I upgraded form the first generation iPhone to the 3G iPhone and noticed that it does not work with all my accessories.
- Doesn't work with the iPod AUX connector in my car, a $350 adaptor
- Doesn't work with the Monster Cable FM tuner
- Doesn't work with the cigarette power adaptor
Charging The most common problem is one in which various accessories fail to charge the iPhone 3G. The explanation for this issue is as follows: most accessories on the market charge iPods/iPhones through either USB or a 12V connection that works through the FireWire portion of the pin connector. The latter method is cheaper, and hence more common. Apple has removed 12V (FireWire) charging from the iPhone 3G; this means that these devices are no longer able to deliver a charge. As such, some accessories will still perform their intended function, but fail to charge the iPhone.
Audio/video connectivity The iPhone 3G is also not capable of pushing audio through some previously compatible devices. This is apparently because of a new sensing mechanism that obviates functionality of non-compliant devices.
Incopmatible or partially incompatible (unable to charge) devices include:
- Monster FM tuner
- Monster car charger
- BOSE SoundDock
- Dension ICE
- OEM iPod Connection Kit for several cars (Mazda 3, Scion XB, Audi)
- Sony XA-110IP iPod Interface Adapter
If you've experienced incompatibility with a specific accessory, please let us know.