… and extrapolating a little from that, we can calculate the approximate amount of heat:
Perhaps I should modify the XP-G2’s rating to 3 peppers instead of 2, since it probably makes about 3/5ths as much heat.
(note: 300 lm/W is the theoretical maximum for a white light)
I see all that, know it’s from the data sheets, and think to myself that somebody needs to put the paperwork away and start building some lights. I don’t have ANY XP-G2 multi emitter lights that come anywhere close to performing like the Nichia 219C multi emitter lights.
Led4power’s drivers do something like this, running a FET between its “open” and “closed” states to achieve a form of current control. It works, but it is unstable at lower levels and it requires the driver to be heat-sinked because extra voltage burns off at the FET chip instead of at the LEDs. This limits the amount of power it can handle, and makes the flashlight significantly harder to build due to the extra heat-sinking requirements.
A more efficient approach is to use a boost or buck driver. However, it requires even more hardware on the driver, and some of that hardware can be pretty big. And it’s extra-complicated when the battery voltage overlaps with the emitter voltage, because it won’t always be appropriate to boost or buck the voltage. So it’s mostly seen with multi-cell lights or higher-voltage LEDs. Or with premium brands like Zebralight, with complicated drivers, but even ZL has mostly switched to higher-voltage LEDs lately to avoid the voltage-overlap issues.
So… the idea does exist in practice, but it has a different set of problems.
The math actually worked out in this case, though. I can’t say whether it’s actually correct or if the numbers just worked out because they were defined in a way which was reversible, but when I multiplied the “Watts of light” numbers by the maximum of 300 lm/W, I got the expected 3300 and 3800 lumen numbers I measured in my light box.
So either the numbers are pretty close to reality, or they’re just clever like those silly tricks where someone can tell you your birthday based on some seemingly random numbers. (spoiler: it’s the latter… but they might be close to reality too)
F$#% are you saying that the damn thing is (54.7/67.37) 82% heat and 18% light! wow i didn’t realize it was that bad!
If you think LED efficiency is bad, look at incandescent lights. Out of a maximum of 300 lm/W, they get like… 5. So, 98% of an incandescent’s output is heat.
LEDs are amazing compared to that. They regularly get over 100 lm/W on medium modes. It may be only a third of the theoretical maximum, but it’s still 20 times better than incandescent.
The D4, at its worst (219c on turbo), gets about 56.4 lm / W, which is 18.8% efficient. However, the XP-G2 model at the max 7135 mode should get about 115 lm / W, which is about 38% efficient.
So it depends. The most efficient LEDs Cree makes can get over 200 lm / W in ideal conditions… but in practice we can only expect about half of that in a flashlight. Maybe two thirds if it has a particularly nice driver.
Not me, but a LEO could find it useful if modifiable to serve as a backup stun device when needed.
LOL……at least Richard and Lisa know what they are doing……
This morning the tracking info for this day, August 3rd, showed still waiting for pick up at MTN
By 11:00 it is shown in Florida.
Now, afternoon of the same day, it is shown at a city a half hour drive from here, on it’s way to me.
No other cities in any part of the country are shown.
Hank must have an inside with Chinese development regarding Quantum Entanglement.
First they keep details hidden about the D4 almost until their release.
Now we have to wonder if he passed some secrets to RMM, who now seems able to teleport the D4s at least part of the way.
Got mine in the mail this afternoon from mountain. Shipping was very fast considering I ordered it this week. My high drain cells haven’t arrived yet so i haven’t been able to see it at full brightness yet but I love the tint of the xpl-hi A3 emitter.
Any idea why the light would repeatedly step down 5 seconds after turning on full output? the light is not hot at all and the thermal regulation temperature is set to the maximum.
What battery ledalex?
A low quality battery, EBL. Claims 3000mah but I tested it and it’s only around 2k. I have samsung 25R (20a) batteries coming in the mail from china.
Maybe the cells sag a lot (voltage drops real hard due to high current), testing with low quality cells is well, not testing.
_ a _ low quality battery? Just one?
Well I’ve tried 4 of the same brand of low quality batteries with the same thing happening. They’re not old batteries, just cheap ones. I don’t think they’re rated for more than 7a, maybe less. All my good 18650 batteries are protected which obviously don’t fit in this light. I’ll drive to a store tomorrow and pick up a samsung 25r or 30q and try one of those.
The light does not step down with these when it’s in tactical mode, however. Maybe that disables the step-down though.
Need high-drain high-quality batteries for this light.
Samsung 25R or 30Q should work much better.
I have some 30Q for wow! factor, but really my idea is use with Sanyo GA.
No way a crappy EBL battery would sustain enough current for this light to work properly more than a few second…
The battery current capacity is low, and then it sags under the load…
Get some 30Q or 25R and you won’t have any problem (apart from burning your palm/Pocket/table/house)
What looks bad?
You are not going to get 5A out of that ebl battery let alone enough to power this light. I am using LG H2 in mine and have zero problems. I tried one of my 30qs and it works great too.