XM-L T6 LED and other LED confusion

When I Google Cree XM-L T6 drop in module, I get dozens of hits for the product from suppliers such as Amazon, DX, Fastech, etc. offering this product ranging from 450 lumens at 1500 ma up to 1000 lumens at 3000 mA. When I look at the Cree Data Sheet I see information indicating the design is 1000 lumens at 3000 mA. How can the Cree XM-L T6 drop in module be offered in so many different lumens and driving currents? I’m obviously ignorant about electronics so I would appreciate some assistance wading through this confusing maze of possibilities.
My goal is to use one 18650 Li-Ion battery to throw between 500-1000 lumens continuously for 2+ hours before changing out batteries. The challenge is to choose the correct Cree Cool White LED drop in module and the correct capacity 18650 Li-Ion battery (2900-3600mAh). This cool white drop in module is encased in a water-tight PVC compartment with a clear Plexiglas lens powered by one 18650 Li-Ion battery at 3600 mAh via internal teflon coated silver-clad copper wire. It is used underwater and needs good illumination up to 2+ hours before changing out batteries. I have built three prototypes and use them personally but my run times have been limited to a little over one hour. Before I market it I need to get more runtime. Please help.

There is a lot to learn about this hobby.

This can help a lot when determining what is a fake description of the performance. Generally don’t trust any listed lumens unless someone has measured it or it’s from a company known for accurate measurements of flashlight specifications.

If you want 2 hours at 500-1000 lumens you’ll need a 3400 mAh cell and a 1400mA driver and you’ll have to suffice with the lower end of your lumen desire (around 500).

Thank you so much for to the point information. Both the XM-L and the XP-G can deliver @ 400-500 lumen at @1.5 amps. Is it better to drive the XP-G at the high end of its current draw or the XM-L at its lower end of its current draw. I would think its better to regulated the current output as close to its design parameters as possible. I’ve been waved off from Ultrafire or anything that ends in “fire”. Any supplier of these LED’s that are reliable and within reasonable cost? I’ve read good reviews on Brinyte. Any others? Again, thanks for the info

Some of the vendors you listed like Fastech will likely take a month to 45 days to get your product. Only use Paypal

Different color tints, like cool white, white, or high Color Rendering Index will have a different perceived lumen output by each persons eyes.
To complicate it even further: Tint, Binning, and CRI Explained (For XM-L LEDs)

How do you plan to shed heat with a sealed PVC container? 1K lumen out of any led is gonna get hot. For that reason alone, I would not want to overdrive things.

Also keep in mind that most lights are going to step down in output as they heat up and voltages drop. So you may have 1k lumen for 5 minutes, then 30 min later same light is putting out 500 and so on.

Just some non technical thoughts.

The light compartment is sealed but always submersed in ocean water. So far this has kept the temperature under control and heat has not been an issue.
As far as the step down in output, therein lies the rub. The “lamp” is submersed but no deeper than 3 ft. I need enough visibility at that depth to make out bottom features at a distance of 4 ft from the source in a wide angle to make out objects for at least two hours. At that point I change out batteries.

What about a light that runs on a protected 26650 battery?? That would be more likely able to give you the desired run time. I would only use protected cells!

something like this example??


for a 4000mAh true rating.


I run the Kongs and love them. check out the HKJ chart below the battery pic

Too fat for the compartment.

Those aren’t really design parameters as much as what the package will sustain. Generally you are looking at LED’s becoming less efficient as the current goes up (after you get passed a very low drive current). XM-L is 3.1V typical for 1.5A versus 3.25V for the XP-G at the same drive current. So the XM-L is actually consuming about 5% less power. If you compare output you’re also getting a little more light from the XM-L; not enough to be visibly significant but it demonstrates the efficiency of driving more moderately.

All that said if the module is using a linear regulator (which is common) you won’t see the extra power efficiency from the different Vf because that’s just extra power lost in the regulator. The lower Vf LED will stay in regulation longer though to maintain brightness. Given that you are at the low end of the brightness window you want to try and get the runtime you need, and that you get both a little brighter and longer in regulation the XM-L might be the way to go if you pick a module with 7135 based linear regulation. You’ll stay in your preferred band of output for longer.

For a buck driver, assuming efficiency doesn’t vary significantly based on the other variables, you could see the power savings to the LED give you longer runtime. XM-L still wins in that case - longer running and a little brighter.

The only reason I think you would prefer the XP-G is the more focused beam. The hotspot could be a little brighter since it’s better focused and the tighter beam I believe is preferred in dive lights. XM-L makes sense for lumens and runtime… unless it doesn’t achieve the results you need for beam pattern out the front end.

I think that covers it.