6V MR11 running at 7.2 - work, and for how long?

I ahve a bike light that uses a 6V batt pack, that is now dead. I can get a 7.2 pack and charger for RC in the 3000MAH region for about 25$. MR11 are mostly available in 2 and 12 V flavours.

Will te 6v run, and for how long? they are pretty cheap, so I don't mind if they only last a few months of riding - I'll carry a aspare /ubbthreads/images/graemlins/wink.gif

Tysonb

Re: 6V MR11 running at 7.2 - work, and for how lon

7.3v li-ion packs come off the charger at 8.4v. Bulb life will be zilch when overdriven by that much.

You can put a regulator in series with the bulb to drop the pack voltage.

Re: 6V MR11 running at 7.2 - work, and for how lon

enLIGHTenment,

It all depends on the voltage drop of the pack when driving the lamp. It might only end up a medium overdrive after account for the load, then again it might be way too much. So it depends on the lamp.

Re: 6V MR11 running at 7.2 - work, and for how lon

i assume the 3000 rc pack is 6x sc nimh.
remember that many modern halogens are already at the hairy edge and any overdrive will cut life drasticly.
a good rc pack like that may come off the charger at near 9v
mr11 flashbulb anyone?

Re: 6V MR11 running at 7.2 - work, and for how lon

Where can one get 6V MR11 bulbs in various beam angles/wattages? I'm looking for a 20W with 10-12 degree beam angle.

Re: 6V MR11 running at 7.2 - work, and for how lon

Just crack open the rc pack and take out a cell.

try bulbman.com

Re: 6V MR11 running at 7.2 - work, and for how lon

TurboDog - I am looking for something much more complicated than that!

/ubbthreads/images/graemlins/smile.gif Thanks,

Tysonb

Re: 6V MR11 running at 7.2 - work, and for how lon

well for lack of a better solution, if you are worried about the 7.2v on the 6v bulb, you need to increase the resistance in the current path to the bulb. In a conventional flashlight where the bulbs and powersource are essentially in the same housing, you would have to place a resistor in line. Whereas with a bike light you have a potential advantage. You can use thinner gauge wire running from the battery pack to the lamp to provide a small amount of drop in voltage to the bulb. NOW I AM NOT SAYING TO USE 30GA SINGLE STRAND HERE! You don't want to catch yourself on fire! You will need to do some calculation with regards to bulb current draw at a given voltage, length of wire from battery to bulb AND back. You can probably get away with having 0.6v drop in the lines, giving the bulb 6.6v probably not killing the bulb. However as stated above, fresh off the charger, the pack voltage may be near 9V initially. This will not correct for that, and you may instaflash. From a safety standpoint, I would HIGHLY recommend using a fuse at the battery, of reasonable rating, as these packs can dump 40-50A into a short!

Have used 6v mr11 bulbs for about 3 years 3 hours a week using 7.2v nicad battery packs have not lost a bulb yet.Mine came from maplins a 5 and a 10 watt.Friend of mine runs them at 8.4v with little trouble.

Be advised - 6V MR11's designed for bike light use are not the same as 6V MR11's designed for landcsape/x-mas display lights!

Running the bike light MR11 from 7.2V will definately shorten its life severely, while running the other type at 7.2V seems just about right.

YMMV - John