Surefire U2 with MT-G2 - MULE

I picked up a user U2 on the MP with intentions of swapping out the emitter. It was a Lux V model, (complete with the classic donut hole, blue tinted beam and 100 lumen output). After doing some research I discovered I was limited in the emitter that I could swap in. (MCE, EZ White or the MT-G2) The reflector had a small scratch on it so I started to think about different possible mods. I wanted to challenge myself and do something a bit more complex and decided on this build: an MT-G2 Mule.



This is a project I have been working on a for a few weeks, my emitter showed up today and I was finally able to get everything built!
I sanded down the emitter centering bits and attached a 1' x 1/2" Copper bar. I had to bore out the existing reflector (It's solid and machined into the head) to fit the copper bar and wires.















It's crazy bright now! The emitter height is just about perfect resulting in a ton of flood. 1" off the heat-sink brings the emitter right below the lens. l am very happy with how this turned out!! I have messed up my share of mods in the past, it was nice to take my time, plan and execute!

Surefire U2 MT-G2 Mule
-Emitter: MT-G2 P0 5000K 6V LED (Thanks Mountain Electronics, Awesome service!!)
-1" x 1/2" Solid Copper Heat Sink - Pedestal
Inspired by this thread *HERE*
Thanks for the U2 from Slaps

-Robert

Awesome mod can't wait to see it!


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Wow! Looks like a real hand warmer. It may throw so much light that it will blind you with reflection up close. What size cells do you use with it?

Interesting mod! :thumbsup: I suppose you still use the stock circuit?

RI Chevy said:

Wow! Looks like a real hand warmer. It may throw so much light that it will blind you with reflection up close. What size cells do you use with it?

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No problem with reflection, I use low most of the time anyway. When on high it definitely lights up everything with even bright light. I use a 17650, cant fit 18650. I've left it running on high for about 30 min without holding it. It gets warm but not HOT, I don't think the MT-G2 is being driven very hard on high.

Icarus said:

Interesting mod! :thumbsup: I suppose you still use the stock circuit?

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Thanks! Yes I did, I like the utility and output levels from the stock circuit:
32mA - 63mA - 121mA - 258mA - 569mA - 1,374mA

Low is a very usable level now, perfect for walking around without being too bright.

-Robert

Excellent! Thank you.

If I'm understanding correctly, you are able to run the mtg2 in this host from a single cell?

That's weird my U2 fits an 18650 but I have to put it in from the front.



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Interesting. Did not know the early versions of the U2 had a driver putting out 6 volts? Any chance the OP measured the voltage across the LED to see what the driver output is? I have modded my share of SF lights and the ones with a Lux V were a bit too variable in output to be predictable for any planned LED choice. Most were about 5.4 to 5.7 volts across the LED which is not enough to drive an EZ white. At least not very well. Fine for an MCE though. Tried that already. An EZ White wants 6.2 to 6.5 volts to be driven correctly. Never thought about a mule though using an MT G2? Looks great I must say. But the latter U2 version drivers do well with an XPG, XPL or XML quite well.

nakahoshi said:

Thanks! Yes I did, I like the utility and output levels from the stock circuit:
32mA - 63mA - 121mA - 258mA - 569mA - 1,374mA

Low is a very usable level now, perfect for walking around without being too bright.

-Robert

Click to expand...

Are you sure about these figures? Then the old LuxV must have been pushed very hard! Normal drive level for a LuxV = 700mA. I'm even more surprised you can get this out of 1 cell. :thinking:

darkknightlight said:

If I'm understanding correctly, you are able to run the mtg2 in this host from a single cell?

Click to expand...

The highest output is slightly lower but the other levels are about the same when using a 17650, have to load the battery in from the head side and its a tight fit. Have not done a runtime test between 2 fresh primaries and the 17650 but I would think the primaries would have a much longer runtime.

m4a1usr said:

Interesting. Did not know the early versions of the U2 had a driver putting out 6 volts? Any chance the OP measured the voltage across the LED to see what the driver output is? I have modded my share of SF lights and the ones with a Lux V were a bit too variable in output to be predictable for any planned LED choice. Most were about 5.4 to 5.7 volts across the LED which is not enough to drive an EZ white. At least not very well. Fine for an MCE though. Tried that already. An EZ White wants 6.2 to 6.5 volts to be driven correctly. Never thought about a mule though using an MT G2? Looks great I must say. But the latter U2 version drivers do well with an XPG, XPL or XML quite well.

Click to expand...

With the original Lux V still in the light I measured 5.7v across the emitter, I thought this would be close enough to the 6v the MT-G2 is rated at. Its working quite well! I need to find a U2A for my next mod!

Icarus said:

Are you sure about these figures? Then the old LuxV must have been pushed very hard! Normal drive level for a LuxV = 700mA. I'm even more surprised you can get this out of 1 cell. :thinking:

Click to expand...

Well, I did not measure them, I found them listed here - LINK

But, let me go get my DMM and check it out for myself!

This is what I am getting (at the tail cap):

2x CR123A:
1. 30ma
2. 60ma
3. 140ma
4. 240ma
5. 600ma
6. 1480ma

1x 17650:
1. 50ma
2. 100ma
3. 190ma
4. 390ma
5. 860ma
6. 1010ma

These are approximate as my DMM is not a very high end model but I would say they are accurate to +/- 5ma

-Robert

Awesome! It looks like you have found the first driver able to power an mtg2 from a single cell!

darkknightlight said:

Awesome! It looks like you have found the first driver able to power an mtg2 from a single cell!

Click to expand...

What driver is being used? Do any of the usual sites like DX carry this driver for sale by itself? The driver in the mtg2 flashlight I put together needs 2 cells.

jason 77 said:

What driver is being used? Do any of the usual sites like DX carry this driver for sale by itself? The driver in the mtg2 flashlight I put together needs 2 cells.

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Surefire uses their own proprietary electronics that I believe they design in-house. There are no other boost drivers able to run an mtg2 from a single lithium rechargeable.

Icarus said:

Are you sure about these figures? Then the old LuxV must have been pushed very hard! Normal drive level for a LuxV = 700mA. I'm even more surprised you can get this out of 1 cell. :thinking:

Click to expand...

All of those current draw figures are at the tail, not at the LED. With one 17650, most likely Vbatt under load is around 3.7V. Assuming driver efficiency of 85%, Vf of 6V and If of 0.7A, we get Ibatt = (0.7A * 6V)/(0.85 * 3.7V) ~1.3A. Since the measured tail current draw is only about 1A, most likely the driver can't reach full regulation on 1xLi-ion, which is what I would have expected. IMO, that's the problem with the Lux V U2. You can't run in full regulation on one LCO Li-ion. Two LCO Li-ions puts the driver in direct drive and risks frying the electronics. You could use 2xLFPs (another type of Li-ion chemistry) to keep Vbatt perhaps just less than Vf. But the battery capacity is pretty low. Of course, you can stick with 2x123A for much greater capacity and thus run time, but then you don't get the benefits of rechargeables.

m4a1usr said:

Interesting. Did not know the early versions of the U2 had a driver putting out 6 volts? Any chance the OP measured the voltage across the LED to see what the driver output is? I have modded my share of SF lights and the ones with a Lux V were a bit too variable in output to be predictable for any planned LED choice. Most were about 5.4 to 5.7 volts across the LED which is not enough to drive an EZ white. At least not very well. Fine for an MCE though. Tried that already. An EZ White wants 6.2 to 6.5 volts to be driven correctly. Never thought about a mule though using an MT G2? Looks great I must say. But the latter U2 version drivers do well with an XPG, XPL or XML quite well.

Click to expand...

You appear to misunderstand how a constant current boost driver works. When you say that most Lux V U2s come in at aournd 5.4V-5.7V for LED Vf, what that means is that at the drive current of whatever the U2 uses (let's say it is 700mA drive), the I-V characteristics of the Lux V typically have the LED show a Vf in the mid-5V range. The driver itself isn't regulating the LED at 5.4V or 5.7V. It is regulating the LED at 700mA constant current. The *response* of the LED based on its I-V characteristics results in the 5.4V to 5.7V Vf. I would wager than an LED with a Vf of 6.2V-6.5V at 700 mA would run just fine on the old U2's boost driver, *assuming* that you feed the driver with an appropriate battery stack. With that high Vf, there is no way 1xLi-ion will run the SF U2 driver in full regulation. Even 2x123A could be dicey *if* the drive current of the LED at 6.2V-6.5V is too high. If the drive current is in the 1A range, then there should be no problem. But if it is in the 2A range, then the battery stack might have to deliver around 3A (specifically, Ibatt = (Vf*If)/(driver efficiency*Vbatt) ~ 6.2V * 2A / 0.85 / 5V = 2.9A) and 123A cells aren't going to be happy about doing that.

Justin Case said:

You appear to misunderstand how a constant current boost driver works. When you say that most Lux V U2s come in at aournd 5.4V-5.7V for LED Vf, what that means is that at the drive current of whatever the U2 uses (let's say it is 700mA drive), the I-V characteristics of the Lux V typically have the LED show a Vf in the mid-5V range. The driver itself isn't regulating the LED at 5.4V or 5.7V. It is regulating the LED at 700mA constant current. The *response* of the LED based on its I-V characteristics results in the 5.4V to 5.7V Vf. I would wager than an LED with a Vf of 6.2V-6.5V at 700 mA would run just fine on the old U2's boost driver, *assuming* that you feed the driver with an appropriate battery stack. With that high Vf, there is no way 1xLi-ion will run the SF U2 driver in full regulation. Even 2x123A could be dicey *if* the drive current of the LED at 6.2V-6.5V is too high. If the drive current is in the 1A range, then there should be no problem. But if it is in the 2A range, then the battery stack might have to deliver around 3A (specifically, Ibatt = (Vf*If)/(driver efficiency*Vbatt) ~ 6.2V * 2A / 0.85 / 5V = 2.9A) and 123A cells aren't going to be happy about doing that.

Click to expand...

I think you are right JC. My logic is thinking the Vf is the where the driver wants to push the LED when in reality its about how much current output is true in the drivers design characteristics. Will have to do some further testing since I have an assortment of KL4 and KL5 drivers on the bench. I think most are the 19028 versions?