MR11 Bulb Conversion help wanted

[pacef8]

Hi there, and hello to everyone here from myself in the north of England.

I have a technical question regarding bulbs leds volts amps etc that i don't understand.

So here goes, i have a twin set mountain bike bulb setup


http://www.blt-lights.com/manuals/blt_explorer.pdf

And i want to take out the old mr11 bulbs and fit a cree led kit like this

http://www.cutter.com.au/proddetail.php?prod=cut947

The system is 6 volts, 4.3 amp/hour, sealed lead acid bottle battery
Low beam 6v 6w MR-11 Halogen (avg.run time per full charge: 3.25 hrs.)

How long would i get now on a 370 lumen, and more to the point would this all work together or do i need something else and how easy would it be to solder together.

All the blt system works fine now it just doesn't work for very long and the bulbs are a bit dim compared to the white crees running on my mining caplamp right now. The bodies are aluminium so they can conduct some of the heat away it i use some of that transfer paste stuff and i plan on only using the thing over the colder winter period. Has anyone tried this and or done a better alternative with a narrower beam.

cheers all
pace

Ta
pace:welcome:

 

[Conte]

Well, I'm an Incan guy, so I've barely played with led, but I do understand the math behind runtimes, and they are the same be it Incan or Led.

If your kit comes with the RCD-24-70/W driver listed, and it drive 700ma @96% efficiancy then . . .

100-96=4. Which means the current draw of the driver will be 4% more then the current output. So . . .
700=4% = 728ma current draw.

First a glossary of terms:

"Ah" stands for "Amp Hour"
You battery at 4.3Ah can run a device that consumes:
- 1 amp for 4.3 hours.
or
- 4.3 amps for 1 hour.
Get it ?

1000ma = 1a
You have a 4.3Ah battery. = 4300mAh.
You Cree Kit will consume an estimated 728ma

So, 4300 divided by 728 = 5.9 Hours !

Almost 6 hours straight use from one light.

Furthermore, 370 Lumens is probably about what your High Beam bulb is putting out being a 15watt Halogen, making the the need for both High and Low beams redundant.
At this point you could eliminate a light fixture, and just run the one Led light giving you High Beam, all the time.
Or, you can put the LED kit in both fixtures and run them both at the same time when you want extra light.

As for your other questions, You'll have to wait for a local Led-head to chime in, to find out about the thermals. The chances of someone here putting that specific kit in that specific fixture may be slim, so you may have to find out yourself if it fits.
And, as long as you know your positive from your negative, and are handy with a soldering iron, wiring it should be easy. But then, I've been soldering for 16 years

PS: this runtime calculation is based on the list capacity of your battery.
It might be lower depending on how old the battery is and how you've treated it.
In the future, I'd upgrade the battery to some form of NiCD pack. Maybe even NiMH if you use it frequently and are willing to upgrade your charger.