Don't have one, but I read that if they are going to die they usually do it in the first month. So you are not the only one.
Unfortunately, sad but true. I had it happen with my Rivas, but I got them from Vapor Junction and Travis was wonderful about replacing them even though I was awfully close to the 14-day mark.
These batteries have problems. I love them and use them, but I'm very careful with anything LR. LR atties and cartos can kill those batteries easily. That's what happened to me. The LR carto had a short and took the battery with it.
I don't think it's the charger; after all it works fine with the other battery. Get a spare battery (or two) from somebody who offers a better warranty. You can get a Riva for under 20 dollars from here:
Vapors Etc. - Terms of Use
Ross is a good man and offers a 30-day warranty, much better than most, but not as good as Janty. Rivas are very nice and I actually prefer their button--it's soft and rubberized and doesn't stick. Good luck.
Coupon code: vapezone (10% off).