Just as the Admiral explained a brushless DC motor does not actually run on DC.
It's the controler that runs on DC. The controller, (goes under a lot of other names like inverter, VFD, ESC, processor controlled IGBT, motor speed controller - the list goes on depending the group your talking to) chops up the DC and breifly feeds it to the motor windings in pulses.
The pulses are not all the same polarity some are "inverted" thats where the name inverter comes from. It is actually a form of AC but the waveform is very complex and made up of multiple odd harmonics of the primary AC frequency. Unlike the mains power AC which is sinusoidal at a single frequency (superimposed with a little bit of noise in most cases).
It is very likely many are thinking that VFDs are AC input only, which they are, but the first componant in the circuit is almost always a 6 or 4 diode full wave bridge rectifyer. So you could cut out the rectifyers and run the VFD directly off the solar panels on your roof if you wish.
If you want to put DC directly into the motor ( not recommended) the motor will lock up and will require a very large external force to rotate the motor shaft at all. Brushless DC motors can pull a lot of current so after just a short time with DC connected, the smoke will escape and the motor becomes easy to turn by hand again. It is recommended you allow it to cool down first, of course.