I have several similar lights, and it all depends if they have a current limiting circuit or not wether you can run it much above 13-14V.
The ones i have that have just a resistor in series with each 3 leds, works fine at 12-13V. @14V they're very warm, and when my bank are fully charged in wintertime when the voltage reach 15V; the leds started to melt off...
Edit:
If the light are the 3-led/1-resistor type, it will probably not light up @ 9V...
/edit
I have swapped all those with similar lights that have a current limiter circuit, and those run from 9V to 30V.