So, I ordered these AAA-compatible little C8s with reduced-sized heads for friends at work. They arrived today - all six of them - and while the quality of these thingies is questionable at best, they are functional and fun. The pics are a bit deceiving. The heads and bodies are a tad bit smaller than they look in case you've never had one.
Well, as non-lumephiles, the work crowd just want to get a new batch of triple AAA's and put them in their lights and get back to work rather than me sell them a special battery and a charger. This is why I bought these particular lights--because of the AAA-workability.
These things are throwers something fierce, like the Super Tactics (though a little ways behind it), and not quite as bright, but still respectable--maybe 180 lumens or so. After sifting through which is the worst one in the batch so that I can find and keep it and sell the rest (sold my personal one a month ago), I came across several disappointments.
The first was a light with a chipped reflector. Didn't affect the beam, but it is noticeable when you look at the reflector. The second is one with more noticeable scratches on the outside. So what, right? And then one of them - the one I ended up deciding to stay with - doesn't open at the back end. I have to take the head off to get a battery in after taking the 3 AAA battery tray out. These were cheapies and so I'm gonna do my darndest to not complain.
So I pop in a fully charged 18650 and click it on. This particular light is brighter than all but two others of the batch, and those that are barely equal it. The thing with this one is that it gets freakin' motherluvin' hot within literally seconds of use. My 980L doesn't get near this hot! The light quality stays constant. It survived a 25-minute run-time test just now, but I could barely hold the thing. I put it down and tried to pick it back up and it took some mental resolve to clutch in my hand!
What is causing this? The other lights don't get hot at all - not with any 18650. I noticed the spring is bent near the head where the positive terminal connects, but something makes me doubt this is the problem. Maybe this light was used and the back melted on?
Oh yes it can. Checked the current draw at 4.2? Would not surprise me to find it higher than 1A at all. If the connection from star to body is poor the emitter gets hot pretty quick. Evetually when such temperature reaches the tube it's ineed scorching.
In fact, heatsinking is very good, because the external body surface gets hot pretty quickly (this is what heatsinking is about). If it wasn't good, the cooking LED would just burn its phosphor.
There are two possibilities:
1) LED has very low Vf, which means, when it goes direct drive, it receives a very high current (even ~2.0A)
2) There is something in the circuit, that consumes so much power and gets very hot
Check the current drawn from 18650, and check the head and pill for some places (or objects) that could cause a short circuit.
If the current to the LEDs is the same, the heat produced should be nearly the same. (The R5 is more efficient, but there is so little difference in efficiency that it shouldn’t be noticeably cooler).
The question is: What is to guarantee the currents will be the same? Differences in forward voltage of the LEDs could result in a higher current draw depending on the driver.
Q5 in a C8 head is a nice thrower. Check it with the 3xAAA and see if it gets as hot as it does with the 18650. I bet it runs cooler with the AAA batteries.