The Ipad Mini can be charged through the standard Lightning cable to USB cable. Here's an example charging the Ipad Mini using an ordinary USB car charger.
USB car charger connected to an Ipad Mini
Here's an ordinary USB car charger connected to an Ipad Mini. The result : The Ipad mini battery is charged normally as it's connected with an original but expensive Apple car charger.
This USB car charger takes 12 to 30 Volts DC and converts it to 5 Volts DC with a maximum current of 1 Amp. (5 Watts) The USB car charger is power full enough to charge the 16.3 Watt Ipad battery. The Ipad Mini AC battery charger has the same output power rating.
This in contrast to USB ports of the older computers and laptops, which can't supply enough current to charge the 16.3 Watt battery within the normal charge time. The Ipad Mini then comes up with a notification "not charging" - which is a bit confusing because it does charge the Ipad Mini battery only at a very slow rate.
Inside the Ipad Mini USB car charger
The ordinary Free Link USB car charger is a one chip DC-DC step-down converter.
The USB car charger converts a voltage between 12 and 30 Volts DC to 5 Volts DC with a single 8 pin chip;
The MC34063A or MG34063A chip is made by Motorola and is a generic step-up or step-down DC-DC converter. This chip is found in many USB car chargers.
Here are a few examples of USB car chargers;
Also have a look at the Ipad Mini Travel Case.