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I own a Mini Maglite Pro AA and the chip has a habit of getting really hot. I lubricate and seal every threaded part with Vaseline.

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  • \$\begingroup\$ only the cheap ones with a poor thermal heatsink \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 12 '19 at 22:40
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    \$\begingroup\$ This is a device usage question, far more than a design question. \$\endgroup\$ – Marcus Müller Mar 12 '19 at 22:41
  • \$\begingroup\$ How hot is "hot?" Too hot to touch tends to be around 60C for most people. And even 40C can feel quite warm to the human touch, but that is still not hot for electronics. \$\endgroup\$ – DKNguyen Mar 12 '19 at 22:42
  • \$\begingroup\$ anyways, "hot" is very relative. A well-designed flashlight for long usage will not get the LED get hot relative to its operational limits. But a) that might be a trade-off between size, weight, cost and runtime, and b) what that limit is is not for us to guess, far less how much Kevin's "hot" is in degrees Celsius. \$\endgroup\$ – Marcus Müller Mar 12 '19 at 22:42
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    \$\begingroup\$ why did you make the comment about the lubrication of the threaded parts? \$\endgroup\$ – jsotola Mar 13 '19 at 2:40
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The Mini Maglite Pro AA uses 2 AA batteries, which can run only 2.5 hours, according to their data.

Now consider that AA batteries have typical energy capacity of about 3 W-h, so two of them have 6 W-h. Since the flashlight runs for 2.5 Hr, the flashlight consumes 2.4W. So it looks like the flashlight uses some 2-W LED. Given that the light output is 252 Lumens, it is an older generation of LEDs, and likely has under 25% light efficiency, meaning that 0.5W gets emitted as light, and 1.5W gets dissipated as heat. So we have about a ~2W heater inside the aluminum body. So the chip area will be hot (especially it you insulate it with vaseline), and body will be warm.

As a matter of fact, all real high-powered "tactical flashlights" do have heat dissipation constructions around the LED emitter area. Why the Mini Maglite Pro would be any different?

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  • \$\begingroup\$ Well said and quite an astute correlation. \$\endgroup\$ – Steve Mar 13 '19 at 13:57

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