17670 woes

Hi:

I bought a 17670 Li-ion cell to use in my Surefire U2. My U2 had an opening that wouldn't even fit the 17670, even though it has an inner diameter that can probably fit an 18650 (mine did not have a plastic tube.)

So I drilled out the opening to fit the 17670. It works, but the + contact spring in the U2 sometimes doesn't make good contact with the small button on the AW 17670 cell, and the light won't go until after a swift bonk.

2 of 3 other 2xCR123 lights that I own won't fit the 17670: Fenix P3D and Olight T25. They fit very tightly, so I am too afraid to attempt to shove it all the way in and have it get stuck.

It does fit an old Ledwave X-33, but that light doesn't light at full brightness with the lower voltage.

Well, as long as my U2 remains my carry around at home in the evening light (EEC?), I will be Ok with the occasional loss of contact.

It sounds like the 17670 is slightly too tight in the tube, and is binding so that either:

• The cell is compressing the forward spring so that the rear spring is not touching, or
• The cell is compressing the rear spring so that the forward spring is not touching.

I've had the exact same symptoms with another tight-fitting configuration, just get another 0.001" or so of clearance and the cell should be able to 'float' longitudinally inside the tube and permit both springs to act normally and obtain adequate contact on both ends of the cell.