I just bought a MagSafe wireless charger. Please excuse my silly question! I plugged the charger in to charge itself. After a couple of hours, unplugged it and put my phone on it. Charging did not start. So my question, to use this thing, do you keep it plugged in and just place the phone on it for a charge? I thought this was something like a power bank that you can carry and use where ever. Thanks all!