I'm thoroughly upset. After less than a month's worth of use, the 2x18650 battery pack that came with my Fenix BTR20 died. This morning it measured 1.4V (they're supposed to measure ~8V fully charged.) I charged it overnight (nowhere in the manual does it say NOT to do that, and I'm assuming that both the charger and batteries themselves are protected against overcharging.) The charger has a light to indicate when fully charged, and the 18650s, are well... 18650s, which, when in a commercial product, should be protected.

The pack worked at the beginning of last week, but I had let it sit out in the unheated garage for a couple of days while I was away. That shouldn't kill a battery, if so the batteries would die every time they go on a flight or are shipped across the country! The manual also does not warn against cold temperatures.

I just sent them an e-mail. The fenix products do come with a warranty, 5 years on the light itself and 2 years on the rechargeable battery pack. We'll see what they say how long they take to get back to me. (Hopefully it's quick, I'm pretty angry.)

I'd like to hear more about this problem as it evolves. 8)

Are you sure the charger circuit was switched on? I had that problem when I first tried charging my cheap-o light. It had to be on to complete the circuit.

Just asking...

The battery pack should be able to withstand the cold. Another thing to check, and maybe this is from the cold, is whether the series circuit is intact. Are these removable batteries? Make sure they are making good contact.