XM-L conversion in an old halogen spot light?

I have not yet looked up the specs on the XM-L but recently bought some Q5 powered C8 lights and the addiction is, well, addicting... I just ordered two more C8s with the XM-L. I also have two old Harbor Freight specials that are doing me no good and thinking about converting them to the XM-L bulb. They both lost their battery but are big lights with a decent reflector/lens package. My goal here would be a decent light with really good throw that would run for hours. I have not decided on battery options yet. The old one was lead acid. Heavy but I don't plan to carry it all over. I would prefer something that will plug into a vehicle to charge and use if needed.

I am electronically inclined and do not mind tuning with a regulator/current limiting circuit if needed. I was thinking of building/buying a LiON pack for this use or maybe go back to lead acid. I have plenty of room in these lights. I am also open to other bulbs. Just looked like the XM was a good bulbs at a good price. Not looking to break the bank in this build..

As far as i know i do not think anyone has modded a big halogen with a LED, as it is popular to fit a automotive HID kit into them and turn them into a 4000lumen+ throw monster .
For me i did a HID mod because it was an easy mod as its mostly a bit of cutting plastic and the hid bulb will plug straight into the reflector without any problems.
Then you have a really bright light that justifies the weight of the light that should run for 50mins+ on a 7ah lead acid, keeping with the lead acid you will have no problems plugging it into the cars cigarette lighter so you can run it for longer.

I would suggest looking at the below link as it details the mod very well.
http://www.candlepowerforums.com/vb/showthread.php?336625-OK-I-ve-Finally-Done-It.
Although it may not run for hours on a lead acid but it would sure be bright and throw very well.


With fitting a XML into the light the main problem would be finding a heat sink that would work well in the bigger spotlights not a massive problem if you are handy with tools or can find something that will work but as the most halogen spotlights are made of plastic you would have to make sure it would not get overheated in there maybe a small fan to help things along.

Then its a case of getting a suitable LED driver that can be run off the power source of your choice.

Never done much in the way of LED mods myself so i think someone else would be better placed to help you in that area but just wanted to point out some info so that it can help you make decisions about what you want to do.

i have tried, not once, and not with just one light, all those big reflector lights (xx million candlepower) don't work right with led, their reflector can't focus it. not to mention cooling problem, those hosts are good (for the most part) to convert to hid. not leds, in conventional way, that is.
i did get one such light to work with xm-l, but i had to get rid of stock reflector, and i had to make an active cooling, with a help of 2 fans, the light is in my avatar, that big gray light, used to be 5000000candlepower searchlight, now it has xm-l in 66mm deep reflector from stanley 5w led light, and bunch of other leds, (ww flood, green, red, uv, low ww, and green 20mv laser)

Ah, I forget about the inherently narrow beam of the LED which probably does create conversion issues. I see no reason to buck the bull on that build and was already considering an HID conversion. I was not sure what color temp to consider for a spot light app or where to get a 50w (ish) HID kit for it?? I thought all I could find before were 30w. I want to say most HIDs are around the 85 lumens/watt area?