Author Topic: Cree lights and long burn times  (Read 678 times)

wilkyboy

  • "nick" by any other name
    • 16-inch wheels
Cree lights and long burn times
« on: December 12, 2016, 02:15:54 pm »
I have a Cree lamp I bought in 2013 with four LEDs and three power settings.  I discovered a FOURTH power setting — by double-tapping the power button I get a super-low power setting.  It turns out that most of the time this super-low setting is more than enough to ride with and — rather pleasingly — gives (from memory) 12+-hour burn times from a 4x18650 battery pack.  The lamp is completely cold when using this power setting, so there's little or no energy wasted as heat — on full power you could fry eggs on it, it's so hot.

Anyway, nearly four years later I bought a new lamp, single LED, but no super-low-power setting.  The lowest power setting is much brighter than I actually need MOST of the time.  Is there an easy way to modify the circuitry to lower the power output to something still useful and also longer-lasting?

Given that you can get these lamps for under a tenner on eBay, I am prepared to experiment, I just have no idea where to start  ::-)

FWIW, this is for my MTB for a bit of bikepacking in 2017, so no dynamo wheel and no desire to build one up, yet.  EDIT: and a desire to take as few batteries as I can get away with  :thumbsup:
Back on the single-RRTY treadmill, whew! :)  LEL-ahoy — X32

Re: Cree lights and long burn times
« Reply #1 on: December 12, 2016, 03:20:56 pm »

Given that you can get these lamps for under a tenner on eBay, I am prepared to experiment, I just have no idea where to start  ::-)

Is there a simple way of modifying it? Probably not.

You are starting with unknown circuitry.

If you were starting with a lamp and wanting to create a circuit, that's not complex, it's just components, switches and soldering. Making that into a small waterproof and robust package can be a bit of an exercise in patience and frustration.
<i>Marmite slave</i>

wilkyboy

  • "nick" by any other name
    • 16-inch wheels
Re: Cree lights and long burn times
« Reply #2 on: December 12, 2016, 04:39:34 pm »

Given that you can get these lamps for under a tenner on eBay, I am prepared to experiment, I just have no idea where to start  ::-)

Is there a simple way of modifying it? Probably not.

You are starting with unknown circuitry.

If you were starting with a lamp and wanting to create a circuit, that's not complex, it's just components, switches and soldering. Making that into a small waterproof and robust package can be a bit of an exercise in patience and frustration.

I'm hoping there's a power/voltage-controller chip in there that could be identified and swapped for a different one.  I just have no idea what it would look like.  The circuit is built onto a board about the size of a 2p piece. 

I'm running the new lamp at the moment to test exactly how long it does run for — it could be it runs for "long enough" and therefore this would be an interesting exercise over Christmas rather than a necessary exercise for my bikepacking endeavours  ;)
Back on the single-RRTY treadmill, whew! :)  LEL-ahoy — X32