I dont know if thats the 12v or 24 volts one.
I do believe thats the curve for the 12v pump at 12volts, equal to the 24 volts at 24 volts.
But i find it hard to believe thats the graph for the 12 volts, at 12 volts, and that it is able to run at 24 volts.
--->Are you sure that the 12volt one rated at 24 isnt the 24volt one?
--->And in this case is the 24 volt one able to do 48 volt?
Maybe im wrong, but in that case it wouldnt consume 14 watts.
Still a very nice pump indeed.
I checked the site
http://www.oberread.com/
And theres this: