A Multiple-Receiver-IPT-Based Voltage Equalizer With Voltage Doublers for Battery-String Charging

Inductive power transfer (IPT) voltage equalizers enhance battery string capacity by enabling simultaneous charging and balancing. Existing multiple-receiver IPT-based equalizers fall short for multicell strings, as they require a dedicated coil for each cell, leading to coil and component proliferation. A new IPT voltage equalizer with voltage doublers is proposed to mitigate this issue. The diodes in the voltage doublers, through their unidirectional conduction characteristics, naturally split the induced voltage at a receiving coil into alternating half cycles, allowing for the sequential charging and balancing of two cells, thereby conserving components. The equalization principles for two cells within a voltage doubler and across multiple cells in various modules are analyzed. The performance validation of the equalizer is conducted using a prototype with three coils and six cells, with experimental results confirming efficient system charging and balancing for ultracapacitor and battery strings.