Apple iPhone 4 does not recognize my DC car charger Apple iPhone 4 does not recognize my DC car charger AC charger works fine. I bought a new DC charger and it still does not recognize that charger. I took it back and exchange it for another one and it does not recognize it as ever being plugged in. I did not buy a cheap charger—that was a $30 charger.
The most likely explanation is that this is a generic charger not designed/tested for use with an iPhone. Have a look here for a more detailed explanation, but in a nutshell, iPhone-compatible chargers need to put out some very specific voltage levels on the USB data (NOT power) lines to be recognized by the iPhone.

So, unless this charger specifically states that it is iPhone-compatible, it just won't work without internal modifications, and you should just return it and get one that is made for iPhone.