Keron Baptiste

It's mostly you (sorry!) but it's fixable. Lithium-ion cells age much faster when they are hot AND at a high state of charge at the same time. Your car mount is the worst case: hot dash, sun, navigation working the CPU, and fast charging adding its own heat. Swelling is gas from the electrolyte breaking down (and a swollen battery is a fire risk, so stop using a phone once the back starts lifting). What helps, roughly in order of impact: 1. Don't charge in the car while navigating in the sun. If you must, use a slow charger and a vent mount so the AC actually hits the phone. 2. Turn on the charge limit (often called 'protect battery' or similar, caps around 80 to 85%). It's real. 3. Overnight: slow charger, not the fast one. Nothing is in a hurry at 3am. 4. Take the case off when charging in the heat. (And when it does swell, a phone with a pull-tab battery is a 20 minute fix instead of a new phone.)