S/F U2 + 18650 Performance ?

[Brangdon]

Can the U2 take 2 unprotected or protected RCR123s?

I read somewhere that it can handle up to 7 volts. I have some unprotected cells which are rated 3.6v, which is too high, and newly charged they are over 4v which is way too high. Being ignorant and stupid I tried them once, and the LED didn't blow but the rotary switch became erratic. Not recommended. I won't do that again.

Protected cells have some circuitry in them, and if that limits the output voltage to 3v then they should be OK. You need to check their rating, though, because it may not mean that.

To answer the root question, I am another user of a U2 with an 18650. (Singular - I could only fit one in the torch and don't have a spare.) I got mine from Lighthound. I got a charger and a stock of primary 123s as well. It's all still new so no real experience to report.

 

[cy]

NO absolutely don't run 2x R123 in U2. not worth risk of killing light with NO gains. 18650 has more mah than 2x R123 cells.

the new R123 regulated 3V cells might work, but again why? you lose capacity/runtime VS 18650

 

[a99raptors]

What about 17650? I think they can run P60s so I could use those cells on the G2, E2d, L2 and U2, right?

 

[cy]

you could run thinner cell, but you would be losing substantial capacity. but gain more versitility

get both

 

[a99raptors]

OK. So the 17650 is more versatile for the incands and LEDs. But compared to the 18650, just less capacity? Thanks! So which do I go for, unprotected or protected? Any idea on the runtime? Can it also run the executive series lights?

 

[Luna]

NO absolutely don't run 2x R123 in U2. not worth risk of killing light with NO gains. 18650 has more mah than 2x R123 cells.

the new R123 regulated 3V cells might work, but again why? you lose capacity/runtime VS 18650

I'm not saying how I know but the U2 loses some of the levels on RCR123a. Current draw drops to around 868ma an you see a slight increase in output. Just don't do it though, no purpose in it.

 

[Mike abcd]

New U2s have been reported as coming with a plastic insert glued into the barrel that prevents 18650s from fitting. Some have reported the insert is fairly easy to remove, some have had a harder time and some have tried and given up. I can't believe Surefire "supports" 18650s in the U2 when they've taken such an obvious step to prevent it.

I haven't seen any reports of a U2 being returned to SF for warranty issues after the insert has been removed but the possibility would seem to exist that they would regard the warranty as void by the modification if they determined the insert had been removed and re-inserted.

I was about to buy a U2 when the first report of the insert was posted here. I no longer plan to buy one unless SF starts shipping U2s without the insert again. With all the reports of "doughnuts" and switch issues, I'm simply not going to deal with possible warranty issues and have no interest in a light that expensive without rechargeable support.

In it's place I've bought both a VB-16 3.5W Lux III from Wai On and a Quicksilver V Lux V from Emillion along with 3 x R123 and 3 x 18650 and a charger from AW and still have spent appreciably less than the lowest cost for a U2 which is substantially under list. Both the VB-16 and QS V provide more levels and much more flexible power options than the U2. I have no illusions that they are of quite the same quality but the VB-16 is very nice and I expect to be just as pleased with the QS V that I headed to Post Office to pick up this afternoon.

Mike