I plan to use one of these drivers with lithium primaries (1.7v) and it should output the 900mA in the specs. Ill be using a RC-G2 as a host.
I assume all of the details about the Cree LEDs at flashlightwiki.com are measured at 3.7 volts?
That’s where I get confused, as a example I will use 1.2v and 3.6v
Will the 1.2v be 1/3rd as bright as the 3.6v (3 times as many volts) even if they were both using a 1 amp driver?
I don’t have any intention to use Li-ion batteries, I just want to know how the outputs will be affected by the voltage so perhaps I can get some kind of idea of the lumen output from the LED using the driver and batteries.
Also I am not sure for example if different LEDs are going to be more optimal/efficiently with that output than others at specific voltages.
So far I have 3 contenders
Cree XP-G2
Cree XM-L
Nichia 219
The XM-L is able to handle a lot more amps than a XP-G2 but will the XP-G2 have a higher output because its not giving enough power to the XM-L to reach its potential (eg. XP-G2 suited to lower power applications)? And with the Nichia I know very little at all.
Thanks if anyone can shine some light on this subject for me.
Well, if the specs are true then that driver is going to supply 900 ma. In that case any of those LEDs would work, but the XP-G2 would be preferable over the XM-L due to the smaller size. The Nichia 219 would be preferable due to the higher CRI, and the XM-L preferable due to the efficiency.
For that driver I have no way of knowing how it would act on different voltages, but I can tell you for it to supply 900 ma to the LED it is going to be drawing 2-3 times that from the battery.
The driver is a boost driver and will supply the correct voltage to the led for 1 to 3 NiMHs. The 900ma might be a little optimistic with only 1 NiMH. The driver will have a range of efficiency, so with only one battery, I (would assume), that the output might be more like 600ma, two batteries 700-800ma and three batteries 900ma. Now, the driver might be able to put out 900ma constant, but when only using 1 NiMH, it should be stressing it to the limit and that is why I would assume it might put out lower ma with only one battery.
The LED voltage isn't something you need to be worried about. The driver you linked to is regulated, so it will supply the voltage the LED needs.
The only numbers that you need to worry about are input voltage and output current.
The link says that the input voltage range is 0.8-1.7v. Based on that, you should only run a single nimh or a single primary on this driver. If you want to run anything more than 1.7 volts, ask the seller whether the driver can handle it. It might not be designed to handle more than 1.7 Vin.
The output current is supposed to be 900mA. At 900mA there aren't major efficiency differences between the latest gen emitters and your choice of emitter should be determined by the type of beam you want. XPE or XPE2 if you want a tight throwy beam, XPG or XPG2 if you want an intermediate beam, XML or XML2 if you want a floodier beam.
I’ve been eyeing that driver for a RC-G2 of my own, although somewhat put off by the cost (~$7 with shipping) without any prior reviews. Certainly looks good though. I’d be wary of the 900mA drive current claims on a single AA as I haven’t seen any reviewed that reach that and most of the similar drivers I’ve seen are around 500-550mA. Still, 3 nicely spaced modes and memory sound good. For reference, the original driver puts out around 250mA.
As for LED, the Nichia/XP-G die size seems to work well - same throw as the XR-E but more spill. Only downside is that the head won’t screw on far enough to get rid of a few faint rings in the beam, but if you can file down the outside of the reflector that should easily be remedied. For awesome CRI, I’d go Nichia; for output I’d go XP-G2 NW. I do have a XP-E2 NW coming, which should be interesting…
Yeah no problem, I bought them about 10 days ago now. I cant remember when they got shipped but I don’t think they will be much longer than another week away.