What if I mod 2 cell light to direct drive, if I only put 5V voltage regulator on the driver.
WOuld it be any good??
Any dangers?? (that concerns me most :o )
WIll XML stand 5V?
No.
XML will burn and die.
Led emitters need to be current regulated.
When an emitter has its Vf very close to the voltage of a cell (abt 3,6v), it's possible to direct drive it, but it is always a risk. Led emitters have a strange suicide tendency, the more current they get, the more they heat up, their resistance decreases (the contrary of what happens with incan lights) and the current rises more, in a vicious circle that can led to premature failure.
With 5v available at the emitter, it's sure death.
Ya...bad idea just like Rockspider said, except for that last part.
- Direct driver works well for single cell applications, for example one 18650 and one XM-L. As current to the led increases, so does the vf and eventually will balance out before the led burns up. Unfortunately, current will start to increase exponentially past a certain point even though it is still tied to vf. What keeps DD lights like the MF UF P60 drop-in, and the 980L from burning out is a combination of overall circuit impedance coupled with the limitations of how much the current the battery can actually supply. Pro tip - don't do low resistance mods on a DD xml then power it with an IMR 18650, for that would eliminate the previously mentioned safeties.
- 2 Li-ion, assuming those are the two cells you plan on using, would be even more fatal. I've seen even crappy salvaged laptop 18650's put out over 10 amps in a dead short.
- Now if you just want to use two NiZn AA's...go for it. It actually works quite well, although runtime is short.
Thanks Match for explaining much better than I could, there's always lot to learn from your posts 