Why does a magnetic charger hold an iPhone but slip with a thick case?

Main answer · Wecent Editorial Team

Short answer: Magnetic force drops quickly with distance. A thick case adds a gap between the magnets in the charger and the magnets in the phone, so the pull gets much weaker. A heavy case, a smooth surface or a case without proper magnets makes it worse. Use a thinner case, a case made for magnetic charging or a different holder.

How the magnets work

A magnetic charger uses a ring of magnets that attract a matching ring or metal plate in the phone or the case. The pull is strongest when they touch and falls rapidly as the gap grows. Doubling the distance reduces the force by much more than half.

What a thick case does

• Adds distance. Every millimetre of case weakens the grip.
• Adds weight. A heavier phone needs a stronger hold.
• Changes the surface. Smooth or soft materials slide more.
• May block alignment. A case that is not designed for magnets may shift the centre.
• Metal or shielding. Some materials interfere with the field.

What to try

1. Remove the case. If the phone holds well, the case is the cause.
2. Try a thinner case made for use with magnetic chargers.
3. Use a case with built-in magnets or a magnetic ring.
4. Use a charger or stand that supports the phone mechanically as well.
5. Place the charger on a flat surface and avoid steep angles.

For safety and performance

A phone that slips may also lose charging alignment. Do not rely on magnets alone for a phone held at a steep angle, such as in a car, unless the product is designed for it.

Check the pull-force claims

If a charger says it has strong magnets, look for a measured pull force and the test conditions. Cases change the result.

For brands

Say clearly the maximum case thickness tested, and warn that thick cases reduce magnetic hold. Provide a compatible-case list.

Quick summary

The gap is the problem. Use a thinner or magnet-ready case, or a charger designed for thick cases.

A simple hold test

Place the phone on the charger at a gentle angle and slowly tilt the surface. Note the angle at which the phone slides, with and without the case. If the case lowers that angle a lot, it is too thick for the magnets. The test takes a minute and makes the effect of the gap easy to see.

Where this answer says to confirm with Wecent, the detail is not published on the product page and has to come from the datasheet or the factory. General facts come from the regulators, standards bodies or device makers named in the text.