I’ll start stating I never modded a flashlight.
My simple Convoy BD04 is still my favourite EDC. Light output is good, so no modding there.
It does run hot after a while on high. I don’t really care about the heat itself but heat also means energy loss and that means shorter runtimes. And that I do care about.
I’m fully aware that the LED generates a lot of heat that (eventually) heats up the whole flashlight.
Even the tail clicky gets hot. I wonder how much of that heat is coming from the LED.
I’ve read terms like ‘spring bypass’.
So my questions are:
a] Is part of that heat generated by inefficient spring contact?
b] If I could ‘fix’ that, how much extra runtime would that give me? ***
***= Not talking about split second accuracy. But more in terms like “less than 5%”, “somewhere between 5-10%”
While I like efficiency, I’m not gonna risk the life of my beloved 
for 2% extra runtime.
Chargers: 1xBasen BD01 5/5, 1x Gyrfalcon All-88 4/5, LiitoKala: 3x100 3/5, 2x202 3/5, 1x402 3/5., MiBoxer C4-12 3/5.
Flashlights: DQG Tiny III 26650 5/5, DQG Tiny III 18650 5/5, FiTorch MR35 3/5, Haikelite SC26 HD 3/5, Lumintop Tool AA/AAA 4/5, Nitecore LA10, Skillhunt H04FRC 4/5, Sofirn C01 BLF 3200k/5600k 2/5, Zebralight H600Fc 3/5.
Powerbanks: Romoss 30000 4/5, xiomi 1000 4/5, Xtar PB2 4/5, Xtar PB2S 5/5
Springs do get hot in some lights but generally most of the heat comes from the LED.
Bypassing the spring reduces the resistance, allowing more current to flow. This means the light is brighter & the spring is marginally more effecient (The power loss through the springs can be calculated using P=I²/R).
However at higher powers the effeciecy of the emitter drops rapidly, so in reality the overall power loss increases.
Not at all making a case against spring bypasses but do realize by increasing the amount of current capable of flowing you’ll actually be enabling the light to make more heat and drain the battery faster!
RIP SPC Joey Riley, KIA 11/24/14. Now I am become death, the destroyer of worlds.
I understand that reduced resistance allows more current to flow. But isn’t the current regulated by the driver?
Higher current to the LED makes it more inefficient and that could be so much that the total efficiency gets worse as before the spring bypass. But the light gets brighter.
Can I conclude from that if the drive caps the current, for example in a lower setting, the total efficiency does rise?
Chargers: 1xBasen BD01 5/5, 1x Gyrfalcon All-88 4/5, LiitoKala: 3x100 3/5, 2x202 3/5, 1x402 3/5., MiBoxer C4-12 3/5.
Flashlights: DQG Tiny III 26650 5/5, DQG Tiny III 18650 5/5, FiTorch MR35 3/5, Haikelite SC26 HD 3/5, Lumintop Tool AA/AAA 4/5, Nitecore LA10, Skillhunt H04FRC 4/5, Sofirn C01 BLF 3200k/5600k 2/5, Zebralight H600Fc 3/5.
Powerbanks: Romoss 30000 4/5, xiomi 1000 4/5, Xtar PB2 4/5, Xtar PB2S 5/5
If the light is direct drive, then bypassing the spring would allow higher current flow resulting in even more heat and less efficiency and shorter runtime.
If the light is not DD, bypassing the spring would increase efficiency and barely make a difference to heat.
The OPTOFIRE - 4.63Mcd aspheric LED flashlight The SYNIOSBEAM - 10Mcd recoil LED flashlight List of the farthest throwing flashlights
The max output is 650 lumen. Assuming not DD, what do you estimate the efficiency increase to be?
Chargers: 1xBasen BD01 5/5, 1x Gyrfalcon All-88 4/5, LiitoKala: 3x100 3/5, 2x202 3/5, 1x402 3/5., MiBoxer C4-12 3/5.
Flashlights: DQG Tiny III 26650 5/5, DQG Tiny III 18650 5/5, FiTorch MR35 3/5, Haikelite SC26 HD 3/5, Lumintop Tool AA/AAA 4/5, Nitecore LA10, Skillhunt H04FRC 4/5, Sofirn C01 BLF 3200k/5600k 2/5, Zebralight H600Fc 3/5.
Powerbanks: Romoss 30000 4/5, xiomi 1000 4/5, Xtar PB2 4/5, Xtar PB2S 5/5
Really depends on the current and voltage as well as the resistance of the spring, but maybe like 1%?
Could be more if the spring is of a bad material.
The OPTOFIRE - 4.63Mcd aspheric LED flashlight The SYNIOSBEAM - 10Mcd recoil LED flashlight List of the farthest throwing flashlights
According to the listing on Simon’s AliExpress store, the BD04 uses a 4xAMC7135 driver. So, it is a (linear) regulated driver and the current on high is 1.4A (until the battery voltage drops too much to maintain that current).
At that relatively modest current, I doubt resistive losses in the tailcap switch and spring, or the driver spring, are significant contributors to the overall heat output of your light.
Because it is a regulated driver, bypassing the springs won’t result in higher current to the emitter. It will mean that the percentage of total runtime under regulation will be larger, but, again, at 1.4A, I don’t think that’ll be significant.
You can do the bypass if you want, for practice, but I’d suggest getting your practice on a crummier light.
Make sure the switch is in tight, cleanly connected.
Heat in the tailcap is sign of resistsnce somewhere. Maybe a crap switch.
You’ll notice in use the head is the hottest part followed by a cool body midsection then heat coming from the switch end.
A good switch won’t show any noticeable difference in temp there.
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