Bidirectional wireless power transfer (WPT) manages to provide a first aid to a mobile device that is running out of energy in urgent circumstances. To facilitate bidirectional WPT with minimum additional cost, a WPT transceiver reconfigurable for performing WPT and wireless power reception (WPR) is provided. The transceiver is reconfigurable between a differential class-D power amplifier (PA) and a full-wave rectifier. A maximum current charging mode (MCCM) is used to maximize a battery-to-battery (B2B) charging efficiency, by directly charging the loading battery with the rectifier, and by powering the PA with the sourcing battery. No output voltage or current regulation is used. Then the number of cascaded charging stages is reduced from five in the conventional design to three.