Consumer Reports tested four charging mats that promise to make charging the battery on your cell phone easy and convenient. 

You just put your phone on the mat, and it charges wirelessly using magnets.

How fast do they work?

"In our tests we found that the mat that charges the iPhone charges about the same time as the adapter would for the wall," said Consumer Reports'  Gerard Catapano.

Some mats for Androids took a bit longer.

Phones must have wireless charging capability, which is built in to new phones. Others need a special case to work on the mat.

For iPhones, testers recommend the Duracell Powermat for $70. It charges up to three phones at a time.

For Androids, the fastest mat tested was the $75 Energizer Inductive Charger. It can charge two phones wirelessly at a time.