Power Electronics

Hybrid School Bus Employs Phosphate Batteries

Enova Systems has ordered U-Charge XP Power Systems based on Saphion phosphate technology from Valence Technology. Enova Systems, in collaboration with IC Corporation recently won a bid with Advanced Energy to provide up to 21 hybrid school buses to 11 states. Enova is providing the hybrid drive systems for the nationwide hybrid school bus initiative and is evaluating Valence batteries to power the line of buses.

The hybrid school bus project features Enova’s post transmission 80-kW hybrid drive system coupled with Valence’s U-Charge Power System. The system is based on a parallel architecture, allowing the system to utilize both diesel and electric power in a highly efficient manner.

The U-Charge Power System uses Valence’s patented Saphion phosphate lithium-ion technology, which provides long run-time, exceptional cycle life, and safety. Saphion technology combines the power of lithium-ion with the safety of phosphates.

The hybrid drive system recovers kinetic energy during regenerative braking; charging the batteries while the bus is slowing down. This ability to charge the batteries provides additional power for acceleration, making school busses ideal candidates for hybrid technology because of the frequent stops and starts they perform along their daily routes.

The U-Charge XP Power System U24 model is a 12.8-V nominal battery designed in the BCI Group 24 size and operates at standard 12-V lead-acid voltage ranges. This battery is capable of delivering 1500 W continuous through a full discharge cycle and can handle peak loads up to 3800 W.

The U-Charge XP Power System can charge in less than two hours and power is stored at high charge efficiency. Each U24 model includes integrated battery monitoring electronics and is used in conjunction with a U-BMS or application-specific battery management system. As many as 30 of the U-Charge XP Power System batteries can be connected in a series for high voltage applications such as pure electric vehicles, hybrid electric vehicles, marine applications, and power back-up applications.

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