Surefire U2 body extension

[VeryOldseadog]

Does anybody know is subg exist?
I have an idea to use U2 with two 18650G8 batteries for long runtime.
May be Mr. McGizmo will help? /ubbthreads/images/graemlins/help.gif

 

[mokona2]

I think an A19 will fit onto a U2 body. You could always add a couple if you need the additional length.

 

[cy]

don't run bare li-ion in series. also don't know if higher voltage will kill U2.

does anyone know max VIN for U2?

 

[McGizmo]

The U2 has a boost circuit so don't be going 2x Li-Ion there! /ubbthreads/images/graemlins/icon15.gif

 

[VeryOldseadog]

[ QUOTE ]
McGizmo said:
The U2 has a boost circuit so don't be going 2x Li-Ion there! /ubbthreads/images/graemlins/icon15.gif

[/ QUOTE ]
Why only boost? As far as I know for low output the circuit must reduce current and the border between boosting and reducing must be floatig depending on the voltage, am I right? While for some level the current from 18650 is to be boosted, for the same level current from 2x123 is to be reducied. So, are there any edge for max voltage that the circuit is able to reduce ??? /ubbthreads/images/graemlins/ohgeez.gif

 

[AlecGold]

well, if it fits, you could run several li-ion parallel?
then you'll have a lot lot lot of runtime!

 

[VeryOldseadog]

A19 owners, what is exact inner diameter of A19 ?
18650 li-ion is 18 -0.0/+0.07 mm diameter and 65 mm lenth.

 

[wasBlinded]

The U2 definitely goes into direct drive on the high setting above the Vf of the LuxV (6.8 volts on my U2). Two li-ion cells would be way too much. This from my own testing.

Someone else noted that above the Vf, the lower settings have no effect in reducing the current when the voltage is above 6.8, but I didn't test that myself.

 

[Ray_of_Light]

There are other threads on the U2 where this limitation is discussed. From an extensive testing, I can tell you that the U2 is not working properly above 6.8 Volt, as WS stated above.
The new Pila 168A, with 2000 mA/h of capacity, is ideally suited in the U2.
Consider that at the medium settings, the U2 has the highest efficiency of any other LED flashlight.
You can run two protected Li-Ion in parallel if you are after very long runtime. You need to find out your own electrical and mechanical arrangement to achieve this. I prefer to carry spares batteries with me. Consider that is very difficult to remain in the dark with the U2, even if you use the protected 168A.

Anthony

 

[precisionworks]

what is exact inner diameter of A19 ?

I believe the A19 shares the same ID as all Surefire tubes - 0.692"

the 18650 li-ion is 18 -0.0/+0.07 mm diameter and 65 mm lenth.

I've measured dozens of 18650's, mostly AW's 2900mAh cell, but also UltraFire, & RediLast. The AW cells run as large as 18.42mm, & UltraFire/RediLast can go up to 18.60mm.

Someone mentioned that the newest 3000mAh batteries are even fatter, meaning that both the A19 and the U2 will need to be bored above "standard" size. Of course, there is no set standard for light boring ... the tubes I bore finish out at .738"-.739", while other boring services run around .733"-.734".