Surefire U2 battery sleeve

Hi, as I said in another post I purchased 2 SF U2's. I am going to keep the best whitest LED and take the other one and do a Milky mod. My question is I believe both (for sure one) seller told me that they are a newer model and dont have a sleeve in the battery tube. Is there a way to look into there and tell if it has one? What will I see or not see? I always use SF123A batteries, but if I do the mod and I have a sleeve I guess I should get 18650 batteries. Is that a good idea? I am new to LED's, rechargeable batteries and mods. Sorry if this is a stupid and obvious sleeve and battery question.

If you look inside and see a black liner, then it has the sleeve. This sleeve can be removed without a whole lot of trouble. There are some old U2's that fit 18650s and don't have the sleeve, but they didn't make the body that way for very long. If you don't see the sleeve, you probably have the newest body.

I use 18650s in my U2 and like the added capacity, but you can use a 17670 in the newer body and still get the benefits of using rechargables, just with less capacity.

So the difference in the 2 battery 18650 & 17670 types are just capacity in runtime? Where do you buy them? What brand? I guess the charger has 2 slots so you charge both cells and use one and then charge the single cell or does the charger have to charge both cells together (I forgot what that is called)?

I just imagined a SF U2 running with one 18650 and with a Cree Q5 or Rebel 100 LED... That would be THE PERFECT light for me.
I could get an SF U2 with an older body on B/S/T forum, but I guess the emitter swap isn't that easy as on different flashlights and the reflector is optimized for Luxeon LED...

I wish SF would bring us a new SF U2 model with a tube that would accept 18650 batteries..

Nearly everyone around here uses AW's protected batteries:

http://www.cpfmarketplace.com/mp/showthread.php?t=170420

He also sells the Ultrafire-139 charger which charges everything from RCR123s to 17500 and 18500 series of batteries. It'll definitely charge 17670s and 18650s.

Wow, a lot to learn What is the difference between protected and unprotected batteries? What do you guys run, protected?

hcd615 said:

Wow, a lot ot learn What is the difference between protected and unprotected batteries? What do you guys run, protected?

Click to expand...

Lithium Ion batteries can be damaged if the cell is over discharged. To prevent this, you either need to be careful not to drain your unprotected batteries, or use protected batteries. Protected batteries have a voltage cutoff circuit that essentially turns the battery off if the voltage drops to an unsafe level.

I am really learning a lot. I use to be a SF dealer years ago here on the forum and on my website and store and I never heard or knew that. So if you let your light die -dead - nothing with SF123's it can harm the light? Blowup, leak?? So I can guess that it is best to use protected cells so they cut off and dont die all they way????? JA10, thanks for your help. It reminds me when people would call me or come to my store I had to explain what the difference was between all the SF's, battery type, lumens, runtime, HAIII, clickie, LED, incan, pyrex, etc. Back when I was a delear the LED's were easy, they only sold the KL1 and maybe one or two LED's. I am sure you have gone over this 1,000 times before but thanks for helping me!!

To be sure we are on the same page, I was discussing protected and unprotected lithium ION cells. These are rechargeable, and are available in protected or unprotected cells. CR123A cells (like the Surefire Cells) are LITHIUM, so are not rechargeable. I have heard of problems with some lithium cells catching fire when abused in some way, but those are usually cheap cells - not SF cells. Someone else can chime in, but I've never heard of any problem with SF cells, no matter what.

Always go with protected batteries Li-ION, they have a small protection circuit built in on the top of the cell. If you over-drain a Lion cell, then you can't recharge it anymore. This circuit will prevent this. It will also protect from over-discharge (in case there is a short circuit). I think it also protects from over-charge?

You loose a bit of the capacity (because the protection circuit takes some space) but it's much safer. Unprotected batteries can explode under some circumstances.

JA10, yes I understand, SF123 are what I always use, I do not have any rechargeables and I am considering getting them now since I am doing the Milky U2 mod. I assume I will use it a lot and it will be easier and more cost efficient to use PROTECTED cells. Protected seems the way to go.

I definitely agree. If you do use 18650s, LG has an unprotected cell at 2600mah, vs. the 2200 for AW's protected 18650. It's not a big difference, but it adds a little more juice. Not to confuse you at all - but the only light I use unprotected cells in actually is the U2. This is because it is easy to see when the battery starts to die. I don't remember exactly, but I believe someone tested a cell during discharge, and when the U2 dropped down to 1-2-3-3-3 for the 6 levels (as opposed to 1-2-3-4-5-6), then the battery is getting close to being overly discharged.

For me, when level 6 drops off to level 5, I change out the battery. You still do run the risk of leaving the light on though and ruining your cell.

Using protected cells are just easier, but I wanted to add in another $.02.

OK So go with the protected and when they die - recharge! Easy enough. Dummy proof, battery dies - recharge Oh yeah - does the AW charger charge one cell at a time or you have to do both together?

The UltraFire charger has two charging channels and two charging bays, so you can charge 1 or 2 batteries in various states of discharge at a time. The DSD Charger (and some others) have 1 charging channel for two battery bays. That allows you to charge two at a time, but they both have to have the same level of discharge. I'm not sure if that makes sense, but if it doesn't, it just means get the UltraFire

I use the UltraFire charger, and like it a lot. A few times a second it checks each battery individually to be sure they aren't over charged.

JA10, I totally understand. I dont want to charge both at the same time, because then if you only have 2 cells you cant use the light until they both charge. One cell in the charger, one in the light, Ultrafire is the way to go, thanks! Seriously, thanks JA10 for taking the time to teach me about cells!!!

I really don't know much at all, but I asked all the same questions about a year ago ... I try to pay it forward whenever I can, but most questions go over my head

Anyone have a picture of the inside of their U2 WITH the battery sleeve? I have pictures from the sellers of my U2's and I will be able to tell by looking at the pictures if mine have the sleeve until I get them in hand in the next couple days.