The change from 25C to 85C represents a more realistic approach to binning. Having said that… Crap, crap, double crap. I still haven’t finished my previous XML mods.
Love it! having no current spreaders will look nicer in aspheric.Cree is notorious for releasing higher bins later down the road,so I might wait for the better binned stuff to surface.Other companies are really floundering wirh their new stuff,especially SSC with their z series...fail.I'd like a few to play around with,even if they are lower bin first thing I would do is throw some in my outside security light.
i think it’s 20% more from about 20% efficiency —> 5% more energy into light
since every new generation of cree leds seems to have a lower Uf this could be an interesting idea.
I’m going to read up on buck converters, i never liked the idea of burning off excess voltage in linear regulators.
Been lazy about ordering a U3 on copper to pop in my HD2010, and it pays off!
Will be looking for the XML2 in high bin on copper now! Direct drive off a freshly charged king kong with a big jump in surface brightness, this should throw nicely.
Is this a “real-world’ 20% increase in light output with an optimized reflector and driver? Or will it be realistically more or less?
For example, with the correct driver, let’s say a Fancy Fandy hoo-fire ke-hd-2010-5-897 now puts out 875 lumens with a T6. With an optimized driver and reflector, the comparable light with an xm-l2 will now put out 1050 lumens?
Where do you see lower Vf?
Maybe I’m wrong, but when I calculate with the old xm-l’s “temperature coefficient of voltage” which is –2.1mV/°C , I get 3.224V Vf at 3A and 85°C.
3.35V + (–2.1mV/°C * 60°C)= 3.224V
this value for the new xm-l2 is 3.35V
And because of the lower “temperature coefficient of voltage” of the new xm-l2, which is –1.6mV/°C, higher core temp means automatically higher Vf.
Although I believe that lumen ratings are weighted according to the human eyes’ response to the wavelength/power spectrum of the source, so taking into account that these LEDs are white they should really be compared to the theoretical maximum for white light (around 250lm/w) instead of the theoretical maximum for monochromatic 555nm green (683lm/w), which gives a value of about 40% luminous efficacy, meaning nearly 10% less heat.
Anyway, I wanted to put a positive spin on it
To be honest I don’t think the increase in heat from a linear driver will be more than that amount anyway. It’s only a small drop in vf, so it should about balance out heat wise.