how long does it generally take to charge a 11.1 vlt lipo?

Hi;
It depends on the charger and on the Battery  Amps, the higher the longer. Sometimes when the input voltage on the charger, without a.c. input capability, is lower than 12 volts, battery will never get charged at all.

It depends on the rate of charge. Some batteries can only be charged at a 1C rate, which generally takes an hour to charge them.
Some of the newer batteries like the Hyperions can be charged at 5C, so if your charger is capable, you can charge them in about 15 minutes or less. Just don't exceed the recommended charge rate for the battery.

Adding to what has already been said, the answer to your question depends more on battery capacity, in mAH (milli-Amp-Hours), than on battery voltage.

I use 11.1 V LiPo, 2200 mAH on my clone 450 and charging at 1C (2.2 Amps) it takes from 45 minutes to an hour, depending on how long I flew.

and how knackered the battery is, the more knackered the longer it takes, as the amp's drop the closer you get to 12.60v on a 3S lipo the longer it takes to put the last bit of charge in an old battery to a point when it wont stop chargering,
If all is ok you should have a charge time of a hour,