RCR123 or AW 17650 For U2 ???

Quick question, would you suggest RCR123s or AW17650 for daily use around the house and in the yard for a SurFire U2? Thanks.

A note on SureFire customer service... I bought a U2 being aware of the tailcap issues. Sure enough when I got in in my hands the tailcap was sticking. Called SureFire, a few days later I had a new tailcap in hand. Problem was it did not work. Would not even turn the light on. Called them up and told them about the problem. Another new cap arrived Next Day Air and works great. Pretty good service I would say. I only share this because I have seen a few post about them having terrible service. Thought I would let people know that isn't always the case.
-Bake

The best option I can think off is a Leef gear 18650 Body and a 18650 battery.

Out of the two you stated, I'd think the 17670 would be better, but I've heard that the newer U2s will not accept this battery.

Thanks for the link. Would the light still maintain the adjustable levels with those body's? I assume so?

I thought I had read that it would take the 17mm batteries but not the 18mm. Guess I need to do a little more reading.
-Bake

Bake said:

I thought I had read that it would take the 17mm batteries but not the 18mm. Guess I need to do a little more reading.
-Bake

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Depends on which version you have. The older ones, and the ones with the plastic insert will take 18mm diameter cells. The newer iteration is made so those cells don't fit anymore. That's SF's way of telling us they don't want people using li-ions in their lights.

I am pretty sure it is one of the newer ones. No plastic insert and the tube measures right at 17mm. So I guess it is 123s or a new body.

RCR123 batteries will not operate the levels correctly. If you can afford the Leef 18650 body then definitely go for that with a 18650 battery set-up. You will get longer runtime, and save money on batteries anyway.

Bake said:

I am pretty sure it is one of the newer ones. No plastic insert and the tube measures right at 17mm. So I guess it is 123s or a new body.

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greenLED said:

Depends on which version you have. The older ones, and the ones with the plastic insert will take 18mm diameter cells. The newer iteration is made so those cells don't fit anymore. That's SF's way of telling us they don't want people using li-ions in their lights.

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I'm lucky enough to have an 'old' U2 that accepts 18650s. But I can also use 17670s in it with excellent results--the runtime is just less. But I still get respectable runtime even when I use a 17670. Surefire might try to force people to buy primary cells (after all, they sell them), but there are workarounds people have tried including boring out the inside of the body to increase the inner diameter. I would stay away from 2 x RCR123As due to possible safety issues, even if they worked properly in the U2.

I have a friend that works in a machine shop. I may get him to take a look at it. If he thinks he can bore it out I may let him give it a shot. I don't have any 17mm batteries on hand. Does anyone know what the minimum diameter would need to be to fit a 17mm cell, or even an 18mm if there is enough room in the new style body to accommodate them? Thanks for the information guys.
-Bake

I bored mine out to 18.5mm for the 18650 battery. Most 18650 batteries measure 18.2mm to 18.4mm for unprotected batteries, and even larger for protected 18650 batteries.

Bake said:

I have a friend that works in a machine shop. I may get him to take a look at it. If he thinks he can bore it out I may let him give it a shot. I don't have any 17mm batteries on hand. Does anyone know what the minimum diameter would need to be to fit a 17mm cell, or even an 18mm if there is enough room in the new style body to accommodate them? Thanks for the information guys.
-Bake

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Mine measures about 20mm to the inner edge of the threads. Are you able to use protected cells with yours bored to 18.5? That may be getting a little thin on mine. Maybe I should aim for getting it to take a 17mm. Or just pick up the leaf body and be done with it. I would really like to keep the original body if possible though.Thanks again.
-Bake

FlashKat said:

RCR123 batteries will not operate the levels correctly.

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This isn't completely true. If you use the 3.0V rechargeables, the light works just like its on CR123's. If you use the ~3.6V rechargeables, you will loose the levels until the voltage drops off. Using the ~3.6V cells could result in a fried LED, so be careful!

Roger

Thanks, I was a little curious what the difference would be running RCRs rather than primaries causing it to lose the modes.
-Bake

What brand of RCR123 3.0v batteries did you use? I tried the Powerizer brand and it still did not work correctly. I tried my Surefire U2 also with 2 3.6v batteries which it will take, but I also don't recommend.

z96Cobra said:

This isn't completely true. If you use the 3.0V rechargeables, the light works just like its on CR123's. If you use the ~3.6V rechargeables, you will loose the levels until the voltage drops off. Using the ~3.6V cells could result in a fried LED, so be careful!

Roger

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Buy the Leef body. This way you don't have to worry about voiding the warranty, selling as original, etc. I bored mine out, because the Leef body was not available at that time.

Bake said:

Mine measures about 20mm to the inner edge of the threads. Are you able to use protected cells with yours bored to 18.5? That may be getting a little thin on mine. Maybe I should aim for getting it to take a 17mm. Or just pick up the leaf body and be done with it. I would really like to keep the original body if possible though.Thanks again.
-Bake

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Pictures of Leef Body and Tail cap on U2 (available from LightHound)

Can someone explain to me why the 17670 at 3.7V, and 1500mAh, will work on this light that normally uses 2X3.0V, and 1400mAh CR123A's?

Doesn't it mean that it normally requires 6.0V from the non-rechargeable CR123A's? How will the 3.7V from the 17670 work? Isn't it 1.3V short?

Cool, Thanks for the pics Jeffb.

Grun the top level (level 6) will be less bright on the U2 if you use a single Li-ion cell (18650 in my ones). The other levels stay the same. The run time is pretty good though and the loss of a bit of topend is no big deal for many. If you must have max output you'll need primaries or 2 * 3.0V rechargeables.