I purchased my tk15 about a year ago at a florida gun show . I had no problems running it until about 1 month ago . The 1st time i tried 18650 batteries turbo mode would not work . I was told by going gear this was an issue with older tk15 lights . I emailed fenix in china about the issue and they reffered me to fenix-store . After examining my light they said they would send it back to me with the appropriate battery to work the light . I then spoke to one of their representatives who said the difference between high and turbo should be more noticeable . They decided instead to ship me out a brand new light . Judy and Zane from fenix-store are great . They did this for me with no proof of purchase . Fenix in China ran my lights serial number and saw that it came through Fenix-Store in OKlahoma and now i have a brand new light on the way .