How hot does an S2+ get at 2.75A? Comparing an anodised Convoy S2+ with a fluorescent yellow powdercoated Convoy S2+

[Flintrock]

Another good reason to like buck drivers.

[TBone]

@Flintrock, that was my inital feeling. The powder coat is very thin and the area (compared to the thickness) is big. If the surface of the other light would not be black but reflective a powder coat may have the better cooling by emission.
I will know more soon. Stay tuned.

[Phlogiston]

@Hikelite

@Speed4goal

Djozz I actually believe in freezing temps it would stay cool enough with atmosphere and hand cooling. […]

[…] Li-ion simply cannot perform in freezing temps, it performs very bad.
You wont get any high current at all that is why everything is so much cooler.

I just hope this graph makes sense to people, even after the cell warms up still heavily under-performs. [graph in original post]

Another old CPF post where I was suggesting how to assess the likely performance of different cells (mostly Li-Ion 18650s) at very low temperatures.

@djozz

@Phlogiston

This thread gets more interesting every time I come back to it

Here’s an old CPF post I wrote with an alternative approach to estimating what you can get away with in terms of runtime and temperature for highly-driven flashlights.

Thanks for the link, I had never read that. Your approach is a bit different (how much time does it take before it is too hot to hold) which is very practical as well.

Thank you

I’m basically too lazy to build all those nice test rigs you make!

[WalkIntoTheLight]

This was a very informative read. Any idea how the BLF A6 would compare, with its FET +1 driver?

[djozz]

@WalkIntoTheLight

This was a very informative read. Any idea how the BLF A6 would compare, with its FET +1 driver?

The XP-L led with FET+1 driver draws about 5A, so 1.66 times the heat in a comparable package. Still assuming that everything is lineair, the calculation is 20+70*1.66=136.2 degC. That is the pill temperature, right under the led will be hotter. A bit too close to unsoldering temperature of the led for comfort.

Did I not do this calculation already somewhere above in this thread? Edit: found it, post #44: How hot does an S2+ get at 2.75A? Comparing an anodised Convoy S2+ with a fluorescent yellow powdercoated Convoy S2+ - #44 by djozz

[WalkIntoTheLight]

@djozz

@WalkIntoTheLight

This was a very informative read. Any idea how the BLF A6 would compare, with its FET +1 driver?

The XP-L led with FET+1 driver draws about 5A, so 1.66 times the heat in a comparable package. Still assuming that everything is lineair, the calculation is 20+70*1.66=136.2 degC. That is the pill temperature, right under the led will be hotter. A bit too close to unsoldering temperature of the led for comfort.

Did I not do this calculation already somewhere above in this thread?

Yes, you did. But someone else mentioned that the release of heat from the body (convection, thermal radiation) wasn’t fully taken into account. I guess I am really wondering if you or anybody else actually tested it with a FET driver, or in a similar light like the BLF A6.

I know the result will be “freaking hot!”. I’m just curious if it really does get hot enough to fry any electronics or melt solder.

[djozz]

I see, may do that at some point. At this moment I’m behind with hobby-related things (I hate that) so it gets at the end of the list.

[Lexel]

the amount of heat transferred to air and radiated as IR light is not linear to the temperature of the light

so with more heat generated from the LED you cant calculate this linear

[newmember]

At the moment I am waiting for my S2+ with XM-L2 U6-4C and 7135x8.
Are there any measurings for the heat transfer rate from the star/pill to the head on a stock flashlight?
What I am afraid of is that the head is below 60degC and I think everything is allright, while the LED gets too hot and solders out itself or something else.
Best regards

[Lexel]

a DTP star with proper heatpaste has a pretty low thermal resistance to the pill,
or even if you solder it to the pill

the most critical part in heat transfer is the tiny thermal pad of the LED

[newmember]

You are right, but what kind of star uses convoy normally for the LEDs?
Are they good enough for this purpose?

[djozz]

The newest ‘tan’ S2+ from Simon came with a DTP star, but older S2+ Convoys have a non-DTP star which under normal use are fine up to 3A or even higher. But a test like in the OP might not be very healthy for the led on the non-DTP star.

[newmember]

Thanks djozz, that was the information I was searching for!

[Tom_E]

Dang, old thread I missed somehow with some great useful info, and including this great referenced post: candlepowerforums.com Convoy S2+heat. I can testify a 7135x8 in a S2 or equivalent on max is not healthy to leave alone tailstanding without thermal or timed controls.

Thanks again Jos!!

[djozz]

Thanks. There is quite a large gap between temperatures that feel dangerous and that actually are dangerous. That gap can be regarded as a safety distance, or if you are a more calculating kind of person, can be used to get more power out of your flashlight.

[hcanning]

7135*8 and dangerous temps? Heh, my 19-amp S2+ Triple would like a word.

That thing will melt your hands with its heat output. It seems robust enough to just beg for more, though

[Tom_E]

@hcanning

7135*8 and dangerous temps? Heh, my 19-amp S2+ Triple would like a word. That thing will melt your hands with its heat output. It seems robust enough to just beg for more, though

19 amps in a S2+? wow! Must be low voltage LED's.

[hcanning]

@Tom E

@hcanning

7135*8 and dangerous temps? Heh, my 19-amp S2+ Triple would like a word. That thing will melt your hands with its heat output. It seems robust enough to just beg for more, though

19 amps in a S2+? wow! Must be low voltage LED’s.

3 x 219C so yeah! It’s a little beast with a lovely colour cast.

[WalkIntoTheLight]

@djozz

Thanks. There is quite a large gap between temperatures that feel dangerous and that actually are dangerous. That gap can be regarded as a safety distance, or if you are a more calculating kind of person, can be used to get more power out of your flashlight.

I suppose it depends on what you consider to be dangerous. If it’s a danger of burning your hand, then temperatures on the outside of the light probably shouldn’t get hotter than 60C. If it’s battery safety, then 80C in the body tube is probably the safety limit. Safety to the electronics, probably over 100C.

[Josh_V]

Nice test Djozz very detailed, can you guys help me with the next doubt, I bought some 7135’s drivers from convoy, I have the following lights C8’s, M8’s, S2+’s and C8mini’s, what’s the number of 7135’s chips on each light, that will not cause a battery thermal runaway, in case of leave the light unattended on max(100%)?

S2+ grey 77 grams and S2+ cyan 81 grams => 4 or 5 *7135?

Manta Ray C8mini weights about 122 grams and Jaxman M8 is about 117 grams => 6 or 7 *7135?

Convoy C8 150 grams => 8*7135?

Manta Ray C8 is 170 grams => 9*7135?