Andy, A rectifier is a diode. A diode allows electrons to go through it in only one direction and not the other, cathode to anode. All chargers I've seen have 2 diodes and the secondary of the transformer has 3 wires. The middle wire is called the center tap. Google full wave power supply or battery charger if you want to know all the ins and outs of a charger. Diodes can be made using different materials. Edison was the first to invent the tube diode. Today's diodes are mostly solid state diodes.
If you have a smart charger, it has a brain box that turns the charger on and off. Sometimes that goes bad.