TrustFire 3 x CREE XM-L T6- Want to waterproof and run off external 12v...

Hi all,

I’ve lurked around the forums and admittedly most of what you talk about is way over my head. I’m trying to build a handheld flounder gigging light. So essentially I need a bright, low amp draw light I can attach to the end of a PVC handle and hold underwater. I pull a kayak behind me with a 12v deep cell in it to use as a power source.

I just ordered a Trustfire XML T6 off of Amazon and it should be here in a few days. My plan is to drill a small hole and hard wire leads to the battery connectors that run out to my 12v battery. From there I should be able to permanently seal the case so that it is waterproof.

My two questions are this.

1. Is the 12v too much voltage and am I going to fry the driver? If so do I need to wire in a resistor? I’m not worried about heat because it will only be used when it’s underwater.

2. Whats the easiest way to bypass the modes? I just want it to come on bright when I supply power.

Thanks for any help, or any links to old posts that cover these topics. I used the search function but didn’t come up with anything relevant.


The easiest way to do this would be to remove the body tube, solder wires onto it and then fill the gap with liquid rubber. It would be much more waterproof.

For 1 mode I would recommend a simple driver swap, I'm on my phone or else I would link to a good one.

Sent From my Iphone

We're very glad to have you here, Cosmo333_Tx!

Thanks for the tip on filling with liquid rubber.

I’ll try to search through here to find information on a driver swap.

If I don’t end up swapping the driver can anyone tell me if I can just hook he 12v directly to the battery terminals without frying anything?

If the light is not rated for 3-cell operation, then you will indeed release the magic smoke.

Another issue is one of the "12V" battery. It may actually be 13.6V, or higher.

Your best bet IMO would be to source a driver compatible with 14V max.

You could also source a car charger cable for a camcorder (or similar) that is rated for your requisite voltage. This would accomplish the same thing as wiring in a resistor, while being a bit more plug-and-play.

Which triple XM-L did you order ?

Here is a possible solution. Here is a DC to DC converter. EBAY LINK

I have one of these but have never used it as of yet. But it was something similar that I was going to do.


Input: DC 4V to 40V (input voltage must be higher than the output voltage to 1.5v or more. Can not boost)
Output: DC 1.5V to 35V adjustable voltage, high efficiency, maximum output current of 3A.
Features: 36u thick circuit boards, high-power high-Q inductors

Thanks for the feedback. I ordered if from Amazon and the details were a little sparse. So I’ll have to wait till it comes in today or tomorrow and see which one it actually is.

From browsing posts on here I know there are lots of models with different components. Other than the number of batteries it holds is there anything on the driver itself that will tell me its max voltage?

The cell capacity is the biggest clue, but a pic of the driver would likely allow for its ID by one of the forum members.

I do not know if my way will help…

Previously> I also wired my TF-3T6 off some 90amp car batt to be used as flood light…due to the heat, i stick the “head+fins” into a 1.5L mineral water bottle filled with water & leave it there under moon & rain, surrounding the gaps, i used Plasticine, to prevent water from seeping out. (do not know if this is the correct spelling-those coloured clay like things kids play Eg:Play-Doh) .
The part where the wires are exposed i just use plastic bag to cover to prevent rain water from going into the tube.

Then my own fish pump spoilt, i pry open the plastic casing (made a mess with cracked casing) somehow it worked again but with wires all exposed… so to go into the fishtank, i used silicon. I think silicon will work since my fishtank pump did not short circuit under water…

Maybe if you used “solder wires to the points (as chime in by scaru)…something to block out water…

Oh… the car batt i used is > 90amp batt… then i have a voltage meter from old veh, just connect for the fun to see voltage…it shows 14.4v at times, when on it shows average 12.8v to 13.8v when i connect to ten piece 12v {led light bulbs} & 2 piece tf-3t6, do not know if it helps. My longest time gunning my tf-3t6 on high is bout 6 hours. Mid is bout 10 hours.

I got the flashlight in on Friday, it only had the capacity for two batteries, so I just crossed my fingers and touched the leads from a 12v battery directly to the battery terminals and it worked! Whew.

I took the handle down to one chamber, drilled a small hole in the tube, direct soldered wires to the terminals. Then I filled it with some liquid rubber, epoxied the wire hole, and sprayed it all down with some black rubber sealant. Wired on a waterproof plug, and now I’m ready to go!

Thanks for all the input.

Great to hear that it worked for you!
Do take note on the temp, I hv read some burn XML or board?

On my 3t6 gunning on high for bout 1 hour + last time, seems to see steam from the fins when I leave in under light drizzle.

I think if underwater will be quite safe.