Recently I noticed that my iPad was not charging as quickly as it used to. Only a month or so ago I was impressed at how my iPad's battery would easily charge up to the 80% range in a couple short hours, but more recently the same charge time would produce a meager 10% if I was lucky. It was infuriating, and the only thing more infuriating was that I couldn't figure out why. After doing a bit of research this is what I discovered.
Being aware that the iPad requires more power to charge (10 watts), I was sure that I was using the right adapter, the one that came in the box with my iPad. However, I became increasingly aware that I had various iOS power adapters strewn all over the house which looked identical to what I assumed was the iPad charger as well as a few compact adapters, one of which came with my iPhone 4, and others that I just seem to have accumulated from goodness knows where. I suddenly realised that I could have easily picked up the wrong charger and mistaken it for the iPad one. The problem was how to decipher one adapter from the next.
The compact Apple Power USB Adapter, the one that comes with an iPhone 4 or 3GS, is a 5 watt adapter, but it doesn't actually say that anywhere on it. However, it does indicate that the output is 5 volts at 1.1 amps (5V 1A), which means 5 watts (I realised this after a bit of learning about electricity). This adapter will charge your iPad, but at a much slower rate because it only has an output of 5 watts. According to Apple's website, this adapter is compatible with all iPhones and iPod touches as well as what appears to be all previous iPods too, but not the iPad.