I was taking some pictures last night of some stuff i’m selling on eBay and used both my new $6.99 S2+ flashlights for some additional light I was bouncing off my ceiling. They were both on high for 5 minutes or so and one was just warm in the hand but the other light was very hot. I checked and nothing seemed loose and no visible issues looking at the driver. What would cause this? Hopefully it means taking it apart because I was hoping to attempt a mod anyway.
Do they have different drivers? Meaning, how many 7135 chips does each one have?
Also note that the higher the voltage of the battery the more heat will be produced.
the s2+ will get hot on the highest it shouldnt get damaged but running it for longer periods on highest maybe isnt the best.
It would be normal for a S2+ with 7135x8 to get very hot if run on full for an extended period.
If you had two same-spec lights and one was hotter than the other it could be caused by a number of things. For example perhaps one light was in your hand and the other on the table. Your hand will conduct heat away.
Or maybe one light has the pill threads engaging a little better with the casing, so the pill sheds heat into the aluminium case better.
Maybe one battery had higher voltage than other?
They both had freshly charged batteries with similar voltages and according to the Gearbest page should have 7135x6. The drivers appear to be very similar. Maybe it does have to do with the threads engaging better on one. Is there a thermal compound that should be used for better heat transfer?
If the heat transfer is higher the flashlight will heat faster, not slower, rather than all the heat staying in the led and driver damaging the product or reducing the light output. It could be that in the one that heats slower the pill is not tight and the led is loose, so the heat stays in the led.
If nothing else can explain it, it could be that the hotter flashlight has a short when it heats up and the components expand a bit. That can be easily verified because modes would not work in that case. If you have a DMM you can check if the current for both lights is 2.1A as it should be.
FWIW, I have two Convoys, supposedly exactly the same 8x7135 configuration. However, one of them has lower output than the other, uses less current, and runs cooler. It’s not a huge difference, but it is easily measurable.
So, there may simply be quite a bit of sample variation in the Convoys. They’re budget lights, so some variation may be expected.
Frankly, it kind of surprises me, given that the 7135 chips should all behave similar. But, who knows? Maybe 1 of the chips is a dud and doesn’t work? That might explain the issue I’ve seen with my lights.
Does anyone know if the light would work with a dead 7135 chip?
Try it with an 8x 7135 and a Nichia on high 
If the convoy logo was embossed i would have it burned into my hand now
Maybe it is the photo but the drivers do not look the same to me. The Convoy font looks smaller and there are some silver lines on one but not the other. Are there same number of turns in spring?
I bought a 6*7135 convoy from Gearbest once, and it had no thermal compound under the mcpcb. Pull the pill and see if thats the case. I’d be more worried about the one that isn’t heating up as fast.
/\_ +1 Robert
+3
I have the Dessert Tan S2+ with only 3 drivers (7135X3). I purposely ordered it that way, so it would never get too hot to hand-hold, and I could loan it to my wife without concern. Even with only three drivers (approx 344 lumens max) it gets very warm after about ten minutes, just short of too hot to hand-hold.
That’s probably because 7135 drivers are not very efficient when the battery voltage is high. All the “excess voltage” is shed as heat; it’s not used by the LED.
You’d want a light with a boost/buck driver, which is more efficient, and wouldn’t get as hot at the same level of brightness. They’re generally more expensive, though.
One thing I find about the 8x7135 Convoys is that they’re probably more efficient than lights using less chips. All those chips drop the battery voltage a lot, and results in a situation where there is no “excess” voltage. Unfortunately, the side-effect is that the lights are not very well regulated on high.
Well, maybe they’re not as efficient when you consider the entire light. I’m really just talking about waste heat from the driver.
Maybe you could try measuring the tailcap current if you have a multimeter (with fully charged batteries) to check if they are the same at max brightness?
Convoy S2+ on highest mode will produce a lot heat.
I got few unit from different seller.
8×7135 6×7135 normally i use 40% output for cycling light
If you think it gets too hot, you can always remove any 7135. each 7135 is 350mA, so you will loose current, thus less light output, but it will generate less heat as well.
it doesn’t matter if you cant’t desolder properly, if you just break one off, the effect will be the same
I can still hold my 8 chip model after a few min. but much longer after that and it starts getting into ouch territory. After 10 min. Im sure it would burn holes in pockets.
Instead of the thermal compound maybe some thin copper tape would help?