Jetbeam Mk II + 14500 maH Li-ion Batteries

bushido-sig · Feb 9, 2007

I just received my 14500 maH batteries for my jetbeam mkII. The difference in brightness is incredible. One thing that concerns me is the heat output. The jetbeam get pretty hot.

My questions:

Is there a maximum time one should not exceed using these batteries?

Does the high output (brightness) shorten the life of the bulb?

Thanks in advance.

lrp · Feb 9, 2007

I can't remember who had stated here that those cells were not good for the Jetbeam....but I quit using mine. It is hard to believe the output those 14500 cells put out!!

shoe · Feb 9, 2007

I've used both the MK II and the original Jet I until the batteries died. (Protection kicked in)
The Jetbeams were designed so that your hand becomes part of the heatsink so I try to grip as much of the head in my hand to keep it cool. I don't know if it helps but it can't hurt.
I don't think it's the brightness that shortens the life, it's the heat.

jsr · Feb 9, 2007

You think an MKII gets hot?...you should hold an MKI in your hand for a while! My MKI on 14500s got unbearable to hold in about 20 minutes with my hand fully around the head to help with heat dissipation. The MKI drives the LED harder than the MKII (and it's brighter too, but with the con of more heat). It's not brightness, but heat that kills LEDs.
For any Jet1 on a 14500, I'd suggest you not run it for more than 10 minutes...just personal experience based on how hot it gets. On a 16340 (R123A), it gets hot, but not as hot as it doesn't drive the LED as hard as it does with a 14500 (due to difference in internal resistance of the two battery sizes).

shoe · Feb 10, 2007

Looks like you've had some experience with this issue.
I can see from a previous POST of yours.

jsr said:
You think an MKII gets hot?...you should hold an MKI in your hand for a while! My MKI on 14500s got unbearable to hold in about 20 minutes with my hand fully around the head to help with heat dissipation. The MKI drives the LED harder than the MKII (and it's brighter too, but with the con of more heat). It's not brightness, but heat that kills LEDs.
For any Jet1 on a 14500, I'd suggest you not run it for more than 10 minutes...just personal experience based on how hot it gets. On a 16340 (R123A), it gets hot, but not as hot as it doesn't drive the LED as hard as it does with a 14500 (due to difference in internal resistance of the two battery sizes).

LEDcandle · Feb 10, 2007

Well, for the sake of information, my MKI underwent a runtime test with 14500, which means no hands holding the light for the full 30 mins!! Don't know how much that affects the LED but I think the LED is well sinked and the heat transfers to the entire body and dissipates pretty good. Max temp recorded was 49º celsius externally at the bezel area near the LED. Prob the junction temp is 80-90º celsius? Just guessing... if so, its within operating specs (if I remember correctly)

naturelle · Feb 10, 2007

The Mk-2 with 14500 on max heats up to 55°C on the bezel - measured with a pyrometer.

Jetbeam Mk II + 14500 maH Li-ion Batteries

bushido-sig

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lrp

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shoe

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shoe

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naturelle

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