And here's the big bad battery itself!

The battery is rated at 3.82 V and 2900 mAh, for a total of 11.1 Wh, a slight upgrade over the 10.45 Wh (3.8 V, 2750 mAh) of the 6s Plus, and on par with the 11.1 Wh, 2915 mAh cell found in the 6 Plus.

Apple claims battery life will be up to one hour longer than the 6s Plus—that is, 21 hours of 3G talk time, approximately 15 hours of Wi‑Fi internet use, or up to 16 days on standby.