Drop-In Mr-11 LED equiv. to 12W for -40C!

[auroreboreale]

Hi all:

I bike to work year-round, North of 60 in 19 hour long Dec. nights in conditions as low as -40C/-40F.

Every year I try and see if the bike light market has produced an off-the shelf drop-in MR-11 LED bulb that would be as bright as my low-beam 12W MR-11. My high beam is a 22W MR-11 combined with the 12W, in a very simple aluminum/foam/velcro helmet-mount and switch.

The battery pack is a 14V 'c' custom nicad pack and a timer used to recharge it. The pack is insulated and is worn under my outer clothing layers in a waist pack.

Not everything works at -40C, so I would like to keep this set-up going for as long as I can!

Still, it would be nice to lengthen out the burn-time of my 12W low beam MR-11 by replacing it with an LED MR-11.

Suggestions?

Long term, I am also interested in off-the-shelf lighter-weight helmet light systems that would give equivalent light and at least 3 hours burn time.

Cold temperature reliability means not very much plastic used in the light, aluminum/foam/velcro seems less likely to crack unexpectedly.

Suggestions?

We are still into long, late-summer, early-fall daylight here, but it will not be long before the long winter nights return!

 

[Meduza]

I have not seen pre-built MR11 Led bulbs that would meet your requirements,
but it is very possible to put together a MR11-sized setup that would give as
much light as your 12W Halogen setup.

Three Seoul P4 and a 35mm Tri-lens from fraen
http://www.fraensrl.com/images/FL3_Lens_Series_Datasheet.pdf

Combine that with a custom metal housing and a Downboy 500 or 700mA
from the Sandwich Shoppe, hook all led up in series and you are ready to go.

but i do not know of any ready-made solutions...

 

[auroreboreale]

Meduza: Thanks for your suggestion. Because of the extreme conditions I am biking in I am very reluctant to change anything but the MR-11 bulb, as I must avoid uncertain materials in cold weather.

Mange takk!

 

[auroreboreale]

I think I may have found a drop-in LED MR-11 bulb with 6 high-end LED's in it is said to produce 58 lumens.

Is this as much as a conventional 12W halogen MR-11 bulb?

I do not think this LED MR-11 has a glass face-plate in front of it. Evidently making a plastic drop-in face plate to fit my existing CNC fixture would be best, but would it stand the heat of 6 LEDs?

Would I be better off to cast the whole front end of the MR-11 LED bulb in epoxy for weather-proofing?

Here are the specs:

http://www.superbrightleds.com/specs/MR11-WHPx.htm

Would this do the trick?

Let me know what you all think!

auroreboreale

 

[Christexan]

That won't compare to an MR-11 halogen bulb due to the beam pattern. That MR-11 LED bulb is very much a broad "flood" beam, basically naked LED packages, with absolutely no throw forward (pretty much the opposite of a desired bike light which throws a lot of light forward with a modest spill).

Typical halogen bikelight bulbs are 10-25 degree beam angles, the LED bulb you linked is around 130-150 degree.

The idea would work with lenses/optic to focus the beam forward, but even then it looks like they are using "previous generation" LEDs, a 5-6 LED bulb with Cree XR-E LEDs running at a modest 500mA (at around 3.4Vf) with optics would put out in the neighborhood of 600-700 lumens (doing math in my head, correct me if I'm wrong, about 120lm/LED), at 11.2 watts of power (so about twice as bright as a 12-watt halogen bulb, at about the same power). Anyhow, I might (working on prototypes) be able to build you a really nice, one-piece drop-in MR-11 replacement with 3xCree LEDs running at 1A (in freezing temps heat won't be a huge issue) with plenty of heatsinking to operate well (although ventilating the housing will still be a good idea). At those numbers, you'll be looking around 600 lumens, much brighter than a halogen up to 20 watts, with a 25-degree optic (perfect biking pattern), and consuming 3.6*3*1=10.8 watts of power. If I get one finished soon I'll send you a note, I have several MR-11s I want to retrofit (and have done a couple already, but those had customized heatsinks and were direct-wired rather than a true "drop-in" replacement.)

Oh, a 12W halogen puts out around 240 lumens (depending on bulb quality), some of which is lost in useless spill beam artifacts (beyond the useful spill beam), so figure about 200 useful lumens. LEDs with good optics or reflectors waste little of their light, so you'll need to match 200 lumens out the front to equal the halogen bulb. Basically halogen in general is around 17-20 lumens per watt, top-end LEDs now are nearly 100lm/watt (figure 80lm/watt out the front with optics losses).
Oh, one other thing, in the cold temps you describe, the LEDs will be substantially MORE efficient, so you'll probably be over 100lm/watt out the front in below 0F temps. A triple Cree LED at 1A at 0F will likely put out maybe 800 lumens total, so actually about 3-4 times more light than the halogen, for the same amount of power used.

 

[auroreboreale]

This is all very interesting!

Elsewhere tonight I see that Cutter in Australia is presenting a near-drop-in MR-11 3 Cree replacement.

I am obliged to keep everything sealed up as much as I can in my massive CNC aluminum barrel-type MR-11 housing, as when bike helmet lights come inside after an hour or two being cold-soaked outside below -10C, you want the inevitable condensation to form on the outside of the unit. This is why most of us use marine binoculars and diving watches, though the latter, even worn on a line around your neck under your layering system, have been known to freeze at -40C...


The search for a true drop-in MR-11 replacement continues!

enlightenment!

 

[auroreboreale]

All: I am still looking for a drop-in LED MR-11, thanks to everybody for your help!

Meanwhile, here in the subarctic, we are losing 6 minutes of daylight each day, so sunrise is now 0738PST sunset 2008, so I am running in the mornings on LED 'winkie' position indicating lights, and in the evenings winkies plus a shoulder-season NiteHawk LED helmet light.

Both my winkie lights have changed, and their batteries, based on things I have learned from CPF. I have replaced 1990's Vista LED lights with the extremely-bright-for its size SuperFlash red winkie from Planet Bike via the Mountain Equipment Co-Op.

Again, from CPF I found out that I had got a bad batch of 2700mah NiMh AA cells from Not-Ever-Ready (in this case!), so I now have Sanyo Eneloops in AAA and AA size for my winkie lights and the NiteHawk helmet light. The Eneloops were briefly on sale from Dell's Canadian web-site.

I kind of drag my feet before I switch to the winter helmet, as the whole system weghs close to 1.5kg, most of that being on the waist-mounted, insulated ni-cad battery pack...

Still, for full-on winter, I will have to use my winter helmet with the 12W +22W MR-11's, so I am still looking for a 12W MR-11 LED drop-in!

Thanks all!

 

[Christexan]

Okay, okay! Still have to get my new workbench built! (Just moved from another house). Hope I have something soon!