strobing U2

[KEN TYE]

I just got my SF U2 back from repair , they replaced my head with a new one. I loaded my 18650 cell into and it ran for about a minute and then started strobing and when dead. I then turned it off and back on , it started working again and then did the same thing. I put 2 SF 123 in it with the same reslts.called SF and thay said it will not run off a lithium ion battery and that I burnt the light up and it voided my warranty ,WTF!. I explained that I used my old U2 that way for 2 years . they didnt care. they would fix it this time but warned me not to use any rechargables in it as this voids the warranty. has anybody ran into this issue before. maybee I just got a bad light?

 

[Ty_Bower]

I'd guess the light was bad from the start. There's a long history of people running a single li-ion cell (18650 or 17670) in their U2 without any problem. I've never heard anything to suggest the circuit has been changed in a way that would make it otherwise.

Generally, using a li-ion cell in your U2 (or on your KL4) means taking some step to bypass the mechanical reverse polarity protection of the light. In the case of the U2, the positive spring contact in the head is usually just a bit too short to make contact with the top of the li-ion cell. This is because most li-ion cells don't have a button top. I would expect that accidentally loading any type of cell (or cells) into the U2 with the polarity reversed would result in instant death of the U2.

Obviously, running a pair of li-ion RCR123A poses a very real possibility of damage due to overvoltage. Each RCR123A may be as high as 4.2 volts fully charged, presenting a total voltage of 8.4 volts to the U2. This is bad, but I'm sure you already know this.

Next time I'd test the light first with a pair of primary (non-rechargeable) CR123A cells before you start using your 18650 cell again. That way, if there are any problems you'll know it wasn't because of the li-ion cell.

For what it's worth, I've never put anything but 18650 into my U2 and my KL4. I've never had any problems with either light.

 

[KEN TYE]

thats what I thought , I have been runing 18650 for 2 years , what a lame excuse from SF .I got a rma to send back to SF again . I am glad I bought a ASP triad while the U2 is down .it will take RCR123 no problems

 

[FlashKat]

I never had any problems with running a 18650 battery. I even experimented and ran mine on 2 18650 batteries, but only for 10 minutes.

 

[greenLED]

While it's true that using li-ions voids their warranty, it's complete nonsense to say a single 18650 will burn the circuit. It's a light that can take 6+ Volts, how can 3.6V smoke the circuit? I call :bs:

Plenty of CPF'ers have been doing it ever since the U2 came out and, as far as I can remember, this is the first time I hear of a single 18650 "burning" the U2's circuit. 2xR123's is completely different story... but that wasn't your case.

 

[lightemup]

Just my 2 cents, but I don't think its fair to knock the product and manufacturer when you do not comply with the operating instructions and something goes wrong. Especially when they offer to repair the light anyway knowing it was used outside their guidelines.

I apologise if my tone seems negative.