1. Apple started out with the classic iPods, that used FireWire 400, using a power adapter called the “Apple iPod Power Adapter.” It’s model number A1003, and the output is 12 watts (12 volts x 1 amp). It’s about 6 cm. on a side, and should be used with older iPods that use FireWire 400. It looks like this.
#1 (Original) Apple iPod Power Adapter (FireWire 400) 12W
2. The next generation of chargers, arrived when the iPods went 100 percent USB. It was called “iPod USB Power Adapter.” There were two versions. The first version, call it 2a., was the same size as the FireWire version above, about 6 cm square, It is model # A1102, and is rated at 5 watts (5 volts x 1 amp).
#2a. iPod USB Power Adapter (5W) (Original)
The next version of this 5W adapter, call it 2b., was slightly smaller than the original shown above, being about 4.5 cm. square. The model number is A1205, and it also puts out 5 watts (5 volts x 1 amp.) It’s suitable for all USB iPods and the iPhone. (It shipped with the original iPhone.) If you bought several early iPods and worked your way up through the iPhones, you probably have a few of these laying around.
#2b. iPod USB Power Adapter 5W (Revised)
3. When Apple came out with the iPad in April, 2010, its larger capacity battery called for a charger with more power. It ships with the “10W USB Power Adapter” model number A1357. It’s output is 10.7 watts (5.1 volts x 2.1 amps) Unfortunately, it looks just like #2b.
#3. 10W USB Power Adapter (looks just like #2b) 10.7W
If you try to use the old 5 watt adapter (#2a/b above) with an iPad, it will work, but it’ll charge the iPad much more slowly when it’s idle and perhaps not much at all when in active use. So if you have any “#2” type chargers laying around, it’s probably a good idea to mark them as 5W so you don’t accidentally try to use it with an iPad.
4. Starting with the iPhone 3G, Apple started shipping iPhones with the “Ultracompact USB Power Adapter,” although it’s too small to actually print that text on it. The model number is A1265, and it’s about 2.8 x 2.5 cm and outputs 5 watts (5 volts x 1 amp.) Being as small as it is, it naturally suggests that you should only use it with iPod touch and iPhones.
Ultracompact USB Power Adapter 5W
In September, 2008, Apple discovered that some of these Ultracompact adapters had a defect that could lead to the prongs snapping off and offered to replace them free of charge. The replacement adapters have a small green dot next to the prongs.
It’s important to note that you can use the 10W charger (#3) to charge an iPhone. Even though it’s over capacity, both #3 and #4 chargers output 5V, and the iPhone will only take as much current as it needs to charge. There’s no risk of damaging your iPhone. See my comment above about the other way around.
The type printed on the sides of these power adapters is incredibly small; it’s almost impossible to read. I am 20/15 at 12 inches, and I needed a lighted magnifying glass to read the ultra-fine print, output and model numbers. So, as I mentioned above, a permanent marker and a code, 5W or 10W, for some of your #2 and #3 chargers is a good idea.
Nowadays, all iPads ship with #3 and all iPhones ship with #4. (The iPod touch comes with the USB Dock Connector cable but no power adapter.) So there shouldn’t be any confusion moving forward.
Thank goodness.
[This article was updated on 20 Feb 2012 to include the model A1102, #2a]