Overdriving incan bulb question

I did my first "mod" last night. Got the 2D light and dropped a 3toD battery on top of the D cell. Put a 5.2v halogen bulb from RS in. It was definately brighter than the stock 3v setup. I have two more 3toD batteries on the way tha will be dedicated to the 2D, running @ 7.2v on NiMH. How much can I overdrive a bulb? I know that 5.1v blew the 3v (2.8v) bulb. This thing has serious throw as it is, it should really cook when I get 7.2v/9v in it.

I've got a 9v 2d that runs a 7.2v xenon bulb. Really good spot at distance, although it is still a M*G. I generally use about .7 times the voltage or incandescant bulbs. shorter life, but they're cheap enough. Who cares? /ubbthreads/images/graemlins/wink.gif Anyway, the life is not that much shorter...it's not like they flashbulb on me.

The higher the cell rating of the bulbs (ie. 3.7V/3 cells, 4.8V/4 cells etc.) the more cells you can push it with. In general, one extra cell's worth is ok for maximum reliability. From 4-cell bulbs on up, you can try pushing by two cells or more. For example, the KPR112 6V 4-cell bulb runs on the edge at 9V or 6-cells. Basically, the percentage overdrive increment gets gentler the higher the bulb voltage.

Wilkey

I'm using two 3toDs in my old eveready 2D flashlight with 4.8v Krypton bulbs powered by 6 NiMH batteries (7.2v). I have some .5amp & some .75amp, either works OK, obviously the higher amperage bulbs are a little brighter. I never bothered to measure the resistance in the 3toDs, but I've done the same using Hotbeams 6AA holder (I modified some I got from electrolumens). Bulb life seems to be fine, although I rarely use this light - it's an easy to find backup if there's a power outage. This is a big improvement over 2D for little or no cost. Dorcy has some cheap ($3.47 at WallyWorld) 1D size lights using a 4AA holder & the same bulb (.5amp, in mine). I'll soon try a 3 cell bulb. The 4AA holder does NOT fit a M@gLite -RussH