Burning quiestion for weird setup

After much thought i would like to use 10x 1.2V NIMH in series to power a set of 2 mr16 3 or 4 w led bulbs in parallel turning both on only when I really want. Would i need a driver to do this, the internal resistance of the leds dictate aperage draw, or would the setup be inherently flawed? or too susceptable to voltage differences because of the large number of cells. ( though I would be charging each cell individually and checking for bad cells). Also, would it cause issue if I used 2 different types of mr16? I would love a very narrow beam and a wide beam. I am a slow biker so seeing 5-7 secs ahead should not require that much distance. Also would the drop in voltage at such a high amp draw cause issue? It seems that using these was done with halogen bulbs but never really with leds. Very strange

Also is my est of12v at 8W would be 1.5A so 1.4 hour max run time or 12v at 4w w 1 bulb on for 2.8 hour max run time be viable?

these are currently what Im looking at
Tenergy Centura AA Low Self-Discharge (LSD) 2000MAH NiMH / 12pk. $17.01 ac / fs @ s4t
1 PCS 10x AA Size Battery Batteries Holder Box 15V Case With Wire Lead be10aa $4.99
Feit Electric MR16/GU10/HP/LED 35 Watt Equivalent 35W Equivalent 3 LED 120 Volt MR16 GU10 LED Light Bulb x2@$15
or 1 MR16 6W Cree XPE 3-LED 450LM 3800K Warm White Light Spotlight (DC 12V) $16 http://club.dx.com/reviews/text/110524 very high ratings if u trust.


Thanks in advance.

The MR16 has been an alluring bulb size for bikes for quite a while, even back in the days of incandescent bulbs. Such a convenient size, and fairly inexpensive due to the high production volumes for interior lighting.

The Feit bulb is powered by 120vac, which would seem incompatible with your battery power. Probably not possible to use without adding an inverter to your system, which would be quite bulky and inefficient.

The DX 12v light looks attractive, but there isn't much info available about it. Electrically, it would be nice to know what input voltage range it was suited for, and how the light output changes with voltage. My assumption is that the light just wires the three LEDs in series, and adds a small resistance in series too, in order to limit the current. It seems reasonable to assume that you could just hook it up to a nominal 12v battery as you are planning to do.

Personally, I would be interested in the beam width too. Most very narrow beams produce enough spill light to illuminate the road nearby, with the main beam lighting up the road 30 or 50 meters ahead. I'd be surprised if a light designed for interior lighting would have this sort of beam, though. 6 watts of light should be enough, but the beam pattern does matter. If the beam is too wide, the light hitting the road that is close to you will be quite bright compared to the road 30 or 40 meters ahead, making it hard to see the road at the far distance. Increasing the overall amount of light won't improve the situation, because your eyes will adjust to the increased light. For this reason, it is quite important to get the correct beam width.

Your battery calculations sound about right.

Good luck with the project!

thanks for the wonderful reply.
I made a very dumb mistake calculating time. For 2100mah theoretical and 8w draw would be 2/3amp so run time would be 3.15 hours max and for 3 watts would be .25 amp or 8.4 hours which made me switch to this awesome looking 9 watt bulb.

See Rule #3 Do not Hot Link images. Please host on an image site, Imageshack or similar and repost – Thanks Norm


http://www.muchbuy.com/9w-mr16-3-3w-led-spot-lights-lamp-bulb-pure-white-12v-car-aluminum.html 9 bucks free shipping... unbelievable

I feel with this setup I can change my batteries to different voltages, buy a better set of leds, driver, and upgrade to a high quality reflector later down the road. The main expense of batteries, holder and ginormous heatsink will be there for me to work with in the future. At 9 bucks it seems significantly cheaper than the sum of the parts. Some led mr16 have amazing internals but if this one is just 3 leds in series with a resistor than I will amend that.To further hijac my own thread can anyone show me a driver that would work with a 12V power source to run 3 leds ?



When i get the bulb I will tear it down and reseat everything as well as post the guts and beam width on cpd in case others are interested in it.

The information you gave on beam width is most concerning. I see some here many use 6 degree or 9 degree beams while mr16 leds are 30 or 60. perhaps dx or another site will offer a reflector that I can use to upgrade the mr16 with. Any suggestions will be looked at and appreciated.

... Also will 5x2 or 10x1 make a difference in battery temps as both options are the same price.

If you don't mind having an ugly light, it's not that hard to fabricate a housing from aluminum extrusions and plexiglass, both of which can be purchased from the local hardware store. My dynamo headlight is an example of this sort of so-ugly-it's-cute philosophy:

http://www.flickr.com/photos/kurtsj00/sets/72157621965148305/

I also did a Cateye conversion with similar hardware:
http://www.flickr.com/photos/kurtsj00/sets/72157628920533643/

I think I used the Ledil Rocket lens... the "smooth spot" version?? It's got a pretty tight beam, although still not as tight as the original Cateye beam.

Something like a TaskLED driver, or one of the drivers sold by LEDSupply ought to work. I usually make my own, but only because I enjoy the opportunity to design my own stuff.