Does 1 MTG2 cause more heat then 2 XML2s?

I heard MTG2 causes lots of heat but not sure what 'Lots' means. Someone made a good point to me that doubling the voltage cuts the current (heat) in half. Well then surely 1 MTG2 at 7.4 volts has to be cooler than 2 XML2s at 3.7 volts correct? And how about 1 XHP70 vs 2 XML2s? And how about 1 MTG2 vs 1 XHP70?

I have a light that has great heatsink and it is a 4 XML2 light and it can run for almost 20 minutes before getting too hot, what would be superior to produce the least heat, to convert it to 2 MTG2s, convert it to 2 XHP70s, or to leave it alone and just upgrade the XML2s to XML2 U3s? Also would the 2 MTG2 or 2 XHP70 setup produce as many lumens at 4 XML2 U3s? Thanks

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I heard MTG2 causes lots of heat but not sure what 'Lots' means.

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"A lot of heat" is a pretty general statement, without something to compare to.

I would love to hear some heat comparisons between XML2/MTG2/XHP70 emitters all driven at roughly the same current as well. Not so much multi-emitter set-ups, but whatever anyone can offer as a reference would be helpful.


I have XML2's running ~3-5a , and JUST got my first MTG2 today. :twothumbs

My build wont be much of an idea on heat though, only going to 2.6-2.7a with it, and that in short "burst mode" shots. It should be enough to give me an idea if I should build another though. I have a XML2 at 3a thats about twice the mass in the heatsink to compare it to.

I will post more info (including how fast it gets hot) when its done, but its small so should be a bit of a pocket rocket as long as it don't go .

Jim

This is not a particularly useful question. If you assume the MT-G2 and XM-L2 are both about the same efficiency, then it all boils down to how hard you drive them. The upper limit for most XM-L2's today is something on the order of 1200 lumens, or about 12 watts, most of which will be dissipated as heat. The upper limit on an MT-G2 is around 3000 lumens, or about 30 watts, most of which will be dissipated as heat. Efficiency tends to decline with increasing output, so at lower output levels, the efficiency is a little higher, and the portion of energy dissipated as heat a little lower. None the less, the total power being delivered to the LED is going to determine the heat produced. So if you drive an MT-G2 to 2400 lumens, and pair of XM-L2's to 2400 lumnes, the MT-G2 is likely to dissipate a little less heat because at 2400 lumens, it isn't being driven as hard a pair of XM-L2's at 2400 lumens. However difference in heat generated is going to be small, probably milliwatts. If you run the two XM-L2 at a level that produces 2400 lumens, and the MT-G2 at 3000 lumens, it is roughly 24 watts versus 30 watts, and for a given level of efficiency, the more energy that is going in is going to produce more heat. i.e. at 30 watts drive for the MT-G2 versus the 24 watts for the pair of XM-L2's, the MT-G2 is going to dissipate more heat.

In terms of the total system, the higher drive voltage on the MT-G2 is going to reduce the I^2 x R losses relative to the XM-L2. So driver on the MT-G2 is liekly to be more efficient. YMMV

So, in short, its still all about overall watts.
That's easy enough to compare.

The way people have been talking "a lot of heat" I was under the impression the MTG2 was producing more heat than could be accounted for simply by looking at watts.

Thanks for the reply.