Most turboprops will start from their batteries. I don't say all of them, because I have a doubt about those bigger older ones like the electra, but I think it also will.
GPU is preffered because it saves the battery, it is cheap, and since on many Tprops a battery start calls for a warmer start it will also preserve the hot section.
Batteries only give you between 24 and 26V DC, while a GPU will give a continuous 28V and a much better response while starting (less voltage drop).
Starting for a turboprop is usually accomplished by the generator, which serves as an electric motor to spin the turbine. It is much easier to start a free turbine (like the PT
-6) because you don't have to spin the prop. On a single-shaft turbine (Garrett, Dart etc...) the turbine directly drives the prop which makes it harder for the starter motor to turn the whole thing, thus more current drawn.
On some aircraft using the Garrett TPE
-331, like the Jetstream 31/32, during a battery start, the 2 batteries will actually connect themselves in series, thus doubling the voltage. It Makes for a very fresh start, cooler than with a GPU...
Happy new year, all!
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.