How much hour does a 100AH battery takes to charge fully?

The AH stands for Ampere-Hours. This means a 100 AH battery can deliver 1 amp for 100 hours, or 100 amps for 1 hour.

And that's a REALLY big battery. Unless you are looking at the power plant for a Prius, you are probably looking at a 100 mAH battery, where m=milli=1/1000 of an amp-hour. Maybe you ARE looking at a Prius, since you posted this question under Car Batteries, but you also posted it under iPods, so...

In any event, the time will depend on the charger you use. The more milliamps the charger delivers, the faster the battery will recharge. But don't try speeding it up - batteries heat up as they charge, and chargers are designed to limit the current so that the batteries don't overheat and/or explode.