Add my recently purchased Watson Duo to list of those that have failed. Upon receiving the Watson, I charged one set of 3400 mAH batteries for XF; one battery achieved 100% and other battery stopped charging at 20%. Switched to Hahnel, and 100% and 20% from Watson measured as 60% and 0%, respectively on Hahnel. Put batteries in XF and got readings similar to Hahnel. Tried to charge another set of 3400 mAH batteries and nothing... charger is inop (and on its way back to Amazon). Disappointing.