Anti-clickbait title: the US federal regulation limiting cell phone battery capacity.

If you want to skip the click through: 20Wh maximum

https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-C/part-173/subpart-E/section-173.185

I call BS on the regulatory argument. My previous cellphone, a Ulefone Armor 3W, came with a whopping 10,300 mAh Li ion battery. That\s almost 40 W/h, yet I could buy it freely.

I'm not super convinced a 20 Wh battery is much safer than 40 or 50 Wh one. I guess if my phone's battery bursts into flames in my pocket I would want the smaller battery. I would like if the regulation required greater than 20 Wh batteries to use a non-flammable electrolyte chemistry like Lithium Iron Phosphate.