The iPhone 8 is rumored to come tricked out with all manner of changes: an edge-to-edge display, no home button, a fingerprint sensor under the screen, dual cameras, an OLED display panel, and whatever else Jony Ive dreams about at night.

But according to one new research note, the biggest draw for customers won’t be any of these. It will be the oldest, most-requested smartphone feature of all time: a bigger battery.

MacRumors has seen a note from Morgan Stanley analyst Katy Huberty that predicts the iPhone 8 will have a longer battery life than its predecessor. That, alongside the features noted above, will drive huge sales of the iPhone 8 in an upgrade “supercycle.”

“In addition to more modest updates to current iPhone SKUs, we expect Apple to launch a higher priced device with AMOLED display that allows for a curved form factor and longer battery life, wireless charging technology, 3D sensors, and more advanced AI software capabilities. While we see accelerated upgrades for Apple’s highest end users in all regions, our work suggests China users are especially sensitive to new technology and form factor changes.”

The longer battery life isn’t the result of a magical new battery technology, wonderful though that would be. Instead, it’s brutally simple physics: a stacked logic board will make room for a bigger battery, and the OLED screen is more power-efficient. Add that to improvements in software and more efficient chipsets, and the smaller iPhone 8 should have battery life on par with the much bigger iPhone 7s.

Chris Mills has loved tinkering with technology ever since he worked out how to defeat the parental controls on his parents' internet. He's blogged his way through Apple events and SpaceX launches ever since, and still keeps a bizarre fondness for the Palm Pre.