I looked on the DMSI site and didn't find any specs on either their C nor Ku LNBs I looked on the Sadoun site, and didn't find anything useful (to this discussion ) Then, I took a look on a DMSI reseller, IvyStonePlace and found:
BSC211 C-band LNB: DC SUPPLY +15~25 Volts at 150 mA NOISE FIGURE 17° K ( MAX ) OPERATING TEMPERATURE -40° C ~ +60° C R.F. FREQUENCY RANGE 3.4 to 4.2 GHz
That's only one data point and you shouldn't assume yours will work down to 15 volts, but if ya have something fairly new, it might. So, I guess that leaves us performing a test on what we got, huh?