Regardless...
Controllers -should- be rated in amperes -at the highest voltage normally seen. A 15-volt standard would be acceptable. 300 watts 20 amps @ 15 volts SUSTAINED at 45 C would be realistic.
It's like rating an alternator dumping into 12- volts rather than 13 volts.
Give the bozos leeway and they will exploit it. Like MARINE cranking amps on a battery rather than COLD cranking amps. Anyting to confound a simple comparison. If ANY formula offered serves to confuse then it is done out of ignornance or a lie of ommission.
Lumens and db are two other areas that are savaged in this regard.
