On contrary to its 14-inch sibling, the Lenovo ThinkPad T470, the 15-inch variant (T570) offers great battery endurance, especially when considering the form factor of the machine.
You can find the available configurations here: http://amzn.to/2wJcyEe
The notebook uses a dual-battery configuration supporting hot swap (you can swap one of the batteries without switching off the machine). The user-replaceable (external) battery is rated at 24Wh while the integrated one is 32Wh. But if that isn’t enough for you, Lenovo is offering bigger solutions for the external unit, which, unfortunately, add some bulge at the bottom. Anyway, even with the stock configuration, the system scored 550 minutes (9 hours and 10 minutes) on our web browsing test and 453 minutes (7 hours and 33 minutes) on our video playback test. That’s even way better than the 14-inch T470.