No need to repeat the mistakes of the past—we've mastered these handy battery tabs!
The Li-ion battery in the iPhone SE comes in at 3.82 V, 6.21 Whr, and 1624 mAh. This offers a minor (but notable) capacity increase from the 1560 mAh cell in the 5s.
Though it's not quite as capacious as the 1715 mAh cell found in the larger (and more power-hungry) iPhone 6s, Apple states this battery will provide up to 10 days of standby, 14 hours of talk time, and 13 hours of video playback.
Despite the apparently interchangeable displays, the SE's battery connector differs from that of the 5s. So, no chance to supercharge your old 5s, unfortunately.