It is a kind of range-extended electric vehicle (REEV) using a lithium-titanate battery but can use as a hybrid electric vehicle (HEV). The proposal aims to use a battery of just the right size as the power core of the system to help the engine maintain maximum efficiency. The performance of the lithium-titanate battery is between battery and capacitor. It also has anti-overcharge, anti-over-discharge, and high-temperature stability, suitable for use in vehicles. The engine only works when the SOC is low, independent of the power requirement. By increasing the battery to the extent that it can supply the motor, the system directly suppresses the influence of power on the engine speed, and the engine runs completely at the optimal BSFC. The lithium-titanate battery has a rate of up to 5C, which directly shortens the working time of the engine. The battery will not be as large as an EV, and the vehicle still has a certain amount of pure electric mileage. Even without additional charging, the engine can be quickly charged to work in the best BSFC in the shortest time. The difference from the previous REEV is the battery type and engine displacement. The relatively low energy density of the lithium-titanate battery complements the engine instead of an EV with an extended-range engine. The purpose of the extra charge is simply to reduce fuel consumption and improve overall efficiency while on the move. The design of rechargeable or non-rechargeable will greatly increase the flexibility of use. Regarding simulation scenarios with a 75kg driver on board, the novel design exhibits a fuel efficiency improvement of 46.2% compared to the 1.5L gasoline model of the CMC Veryca. Moreover, when accommodating both a 75kg driver and a 600kg cargo load, the new design results in a fuel saving of 42.4% when contrasted with the 1.5L gasoline version.