crash-testing a MT-G2 on a copper Noctigon, graph done, mod done and repaired :-)

MRsDNF · June 26, 2013, 8:57pm

comfychair:

MRsDNF:

Thanks djozz. Terrific effort. If this was running off a nine amp driver, correct me if I’m wrong but the led would only get about 6 amps. If this is the case this driver should be ok.

Nope, not with an actual buck driver (i.e.: not a LD-29 or the like). As long as the input voltage is high enough (with some headroom) above the LED’s forward voltage at the desired current, the driver should do the rated current no matter if it’s a single 3.3v LED or 3 3.3v in series or a single 6v LED. The buck driver in the S1100 does 3.3A to a single XML and 3.3A to a single MTG2. IOS ‘5.5-12v 9A’ driver does 9A to the MTG2 (I hope it’s obvious that I haven’t tested that one with a single XML, lol). The IOS ‘3-18v buck/boost’… see below

MRsDNF:

Running 3 26650 batteries and the 5 amp IOS driver the led sees 3.6 amps.

Wait, are you asking about that one, or stating what that combo actually does? Is that the ‘3-18v’ one, that claims 5A to a single LED or 3.5A to multiples in series? If it is, the 3.5-3.6A you’re seeing is correct… the 6v MTG2 appears to the driver as two 3v LEDs in series. That 5A number is for only a single 3.3v LED. I don’t know why that driver does it that way when other non-boost buck-only drivers don’t care how many LEDs there are/what the total forward voltage is, but that’s what it is advertised to do, looks like it is doing what it says on the tin.

Running the IOS driver you mentioned will run a single XM-L U2 at 5 amps with a couple off 18650.
Running the same driver with an MTG-2 with 2 x 26650 will give you 2.88 amps. Exactly the same setup with three 26650 will give 3.6 amps at the led. Dont ask me why.
I think your measurements for the 9 driver were taken at the tailcap.

Not try to take this thread off topic but to answer questions as they arise here is the results for anyone that has not seen them.