The following information should help people understand why charging the newer Apple products like the iPhone 3G, 2nd gen iPod Touch, and 4th gen iPod Nano, can be problematic and what they should look for in charging accessories. Basically, there are two problems you may encounter when trying to charge the newer Apple products. One is somewhat common among USB-charging devices and the other is specific to these Apple products.
When charging via some type of cable, the common issue is that the device needs to “believe” it is connected to a computer and has a data connection. This is why, for example, your iPod stops charging when you turn your computer off, even though you may have it hooked up to a powered USB hub. (Your iPod thinks “the lights are on, but nobody’s home,” so its not going to charge.)
Manufacturers can “fake” this connection by adding simple circuitry to the charger (AC, car, etc.) or to the USB cable itself. Gomadic, for example, has a different connector tip for just charging and another for normal data. The charging tip has the special wiring. The Boxwave iPod Charging Adapter is a short USB cable with the special wiring. My Creative Zen and Sandisk Sansa Fuze have this same issue, so it is not unique to Apple products.
The second problem, however, is Apple-specific and relates to the fact that iPod was originally only chargeable via Firewire which uses 12 volts; USB is 5V. With the original iPod, you had to charge via Firewire although you could plug the cable into a special AC adapter. When they added Windows and USB compatibiity, the adapter had two cables coming from the dock connector, USB on one side for data and Firewire on the other for power!
Now, obviously since iPods have moved totally to USB; they no longer rely on 12V and are charging using 5V. So why then do many docking speakers not charge the newer iPods or the iPhone 3G? Well, the dock connector specification used by most manufacturers still supply power using only 12V. It’s the way they’ve always done it. They never made the change to support the 5V spec. I suppose this wasn’t necessary since iPods and even the first gen iPhone continued to support charging at this voltage. This all changed with the newer products unfortunately since Apple dropped that backward-compatible 12V support.
There are a few third-party adapters that make the 12V to 5V connector changes. These are primarily designed for attaching to the end of iPod charging cables, but if space and asthetics allow, you should be able to use on a docking speaker. Here are some examples of adapters:
These adapters are pretty expensive even though none of the circuitry changes are difficult or costly. Pretty simple really. I’m guessing that most of the cost is from the Apple dock connectors.
Obviously the different power voltages are running on independing lines on the dock connector. This would allow migration and support for both. Unfortunately, docking speaker manufacturers did not migrate and Apple just stopped putting the circuitry into new products that allowed charging on the Firewire power line. According to Apple, they were warned. (Note that you don’t have to worry about ruining a new iPhone 3G if you plugged it into a device that only supported the 12V.)
So there you have it. If you want to charge your iPhone 3G, 2nd gen iPod Touch, and 4th gen iPod Nano using a cable, make sure it has the special circuitry to make the device think there’s a data connection. You don’t have the 12V issue here because the 5V USB power will be sufficient. Note that this is issue is not specific to the newer devices, so anything that says it will charge an iPod via cable should work.
If you want to charge one of these products using something like a speaker with a dock, it must support the new 5V spec, which most don’t. The only product I can absolutely confirm that has this is the Logitech Pure-Fi Anywhere 2, although it has an issue with the Aux input (read this). I’ve read that the iHome iH8 and iH9 work as well, but I cannot confirm first hand.
My recommendation is to look for something that says it supports the iPhone 3G, even if you will be using it with a 2nd gen iPod Touch or 4th gen iPod Nano. In fact, do not buy any docking speaker product unless it supports them as it won’t charge any future Apple iPod product! HOWEVER, that said, there is, unfortunately, yet another issue with only the iPhones, and that is the additional shielding necessary to eliminate radio interference being heard. So, there “could” be a docking speaker product that worked with the 2nd gen iPod Touch and 4th gen iPod Nano, but not the iPhone 3G.
Note that if the docking speaker supports the new products, it should still work with older iPods. The only things that might not work is the original Firewire iPods. Hopefully, 2009 will be the year that all manufacturers make the change.
If you want more technical info on the pins and such, here are some links:
I hope this information helps people. It took me a long time to put all the pieces of the puzzle together =)
I bought one of the Boxwave iPod Charging Adapters and it does indeed turn the standard iPod USB data cable into one that will allow you to plug the cable into, say, an AC adapter with USB input and it will charge the iPod.