Out of Battery

It’s too bad the concept Yotaphone never took off beyond obscurity. Business in the front, e-ink on the back — the phone can potentially last for days. I was thinking about this what my lazified battery S8 ran out of juice. It was burning more than a percent a minute despite being on mid-level energy savings and all background apps being suspended.
I’m curious how Apple and newer Samsung (and other devices) deal with the last squeeze of juice from their devices. This is likely an area where there’s some opportunity for niche hardware makers.