Magnetic charger just means it does not have exposed plugs you have to plug in. There is a wall plug like a phone charger, then the other end of the cord is a small appx 1.5" disk that has a magnet built in. You put that against the back charging area of the vacuum and it automatically sticks to the vacuum and charges without having to 'plug' into the vacuum. The advantage is if you forget to 'unplug' before grabbing the vacuum the disk will just pull off, no harm done.
I can't attest to how long a charge will last. I've used it for over half an hour with spraying and vacuuming and it's not giving any indication it needs charged again. The LED on the front will flash different times to show when it's getting low and needs charged.
Hope this helps.