Battery test result: Set up my Tascam HD-P2 with the backlight on, phantom power on and powering Busman mics. Recorded for 13 hours 23 minutes before the battery ran too low.
When I tested the Naztech I had the backlight off. With such similar run times, I am confident that these are the same battery. The ebay version is simply unbranded and 45 bucks cheaper.