Originally Posted by robtown
I changed my cygo nightrover from 6watt to 10watt. In combination with a 8.4v RC battery pack I get blazing white light.
Going from 6W to 10W won't do much. Your real gain was in going from a 6V (assuming that's what it was) to a 8.4V battery. Overvolting will reduce the life of your bulb but you gain a whole lot of light output for it. By the way, I popped my first MR bulb this morning on an overvolted system. Considering that this is the first time I've burned out a bulb on using the MR-11 bulbs in over 10 years of using them gives you some indication of their ruggedness
8.4V might be pushing the bulb a little more. Get some spares.