Stacking a magnetic power bank between your iPhone and a MagSafe car mount usually weakens the hold and blocks charging. Here is why, and the setups that work better.

An iPhone-specific look at magnets: why MagSafe iPhones are built for them, what Apple warns about, and how magnets can affect the compass, cards and medical devices.

Do magnets damage phones? A clear look at what everyday magnets can and can not do to a smartphone, from storage and screens to compasses, cards and wireless charging.

Your phone sticks to magnets because it contains several of its own: a MagSafe ring on most iPhones, plus speakers, vibration motors and sensors. Here is what each does.

Why so many phone cases now include a magnetic ring, what it does for charging and car mounts, and when a non-magnetic case is the better choice.

A feature-by-feature guide to your portable jump starter: the first charge, reading the lights, boost mode, USB charging, flashlight and compressor modes, storage, and flying with one.

The quick steps for jump-starting a car with a battery pack, plus fixes for the situations that trip people up: dead-flat batteries, hidden batteries, cold mornings and hybrids.

A simple sizing guide for jump starters: how many amps your engine needs, how diesel and cold weather change the answer, and what battery capacity to look for.

A plain-English explanation of what a car jump starter is, how it starts a dead battery, the main types, and how it compares with jumper cables and chargers.