I would like to see that philips lamp! it does sound very promising.
Bob, the formula for lumen vs voltage involves approximately a cubic equation compared to the voltage increase.. it's actually a pretty simple equation.. (Voverdrive/Vrated)^3.5 x LumRated.
In any event i just plugged in the values for the 5761.. and it's stellar.
RATED output is 25.5 L/W that puts it in league with the IRC lamps!
re-rated for 7.1V (since at 5.5A even with hotdriver you'll only get 7.1 to the lamp from a 7.2V source).. the values are such:
7.21 Vbat
7.1V lamp
110mV drop on the ckt.
5.49A
38.9W
1379 bulb lumen
896 torch lumen (more than an 1185 at 11.1V!)
35.4 Lumen/Watt.. (just about the maximum possible).
CCT 3375 (that doesn't quite jive with the L/W figure so one of them is likely off).. it should be far whiteer than that.
hours: 13.3.. likewise about the CCT.. it's inversely related to bulb life, but the 13.3 is closer to what i'd expect with that CCT.
in any event.. whow.. nice lamp i need to try one.
I'm working right now on a really neat mod.. 2D size.. no boring.. 3AH battery.. the 6.35A draw of the osram is too high for the LiON cells.. but the 5761's 5.5 is below the 6.0A max recommended..
JWL.. expected life at 7.5 of a 64675 is 0.1 second. I ran one for about 1 second at 7.2V.. it's about 1000L.. not worth the $6 per second cost i'm afraid
de-tuned to 7.0V with hotdriver they are just simply stunning. They have that 'white enough to blow' look about them. I think they are very similar to the 64625 in the 'touchy' about overdrive.. i wouldn't recommend any direct-drive solution since it's not really feasible to get 7.0V w/o over voltage direct-drive.
-awr