red555 -I am just wondering where you got the 5 volt limit. The supplied iPad charger says 5.1 volts. I also have a Griffen iPhone/iPod charger that works slowly for my iPad that says it puts out 5.2 volts.
Depending what spec you read, the value for usb will be listed in the 5 volt "range". 5.1/5.2 volts is close enough. No problem.
There are some old connectors out there for firewire charging that have a 12 volt output and that's what I am referring to when I say don't exceed 5 volts.
I also have a griffin charger in my car. I'll see what it says when I go out. It's probably 5.2, like yours.
I probably would have been more correct to say "don't exceed approximately 5 volts."