batteries
Battery problems that are not “just old”
Sudden shutdowns, heat and a lifting back panel are different battery faults. One of them is a safety issue.
A year-old battery that fades a little in winter is normal. A phone that dies at 28 percent, a laptop that only lives on the charger, or a tablet whose glass is bowing is not something to ignore.
Health percentages
iPhones show battery health. Many Androids do not. Either way, behaviour matters more than a number on a menu. If the device is hot while idle, stop charging overnight and book a look.
Swelling
Do not press a swollen battery flat. Do not clamp the case. Bring the device in and mention the swelling on the form.