Why do hybrid cars have two batteries? What is the estimated life and replacement cost?

There are various methods for hybrid systems

Since the introduction of the Toyota "Prius" as the world's first mass-produced hybrid vehicle in 1997, hybrid vehicles have become widespread. [Image] Toyota releases an EV of 1.65 million yen! You can buy this! You can use it! (12 sheets) Hybrid vehicles are becoming popular because they combine a gasoline engine and a motor to enable environmentally friendly driving.

Engine room of Toyota "Prius", a representative hybrid

Hybrid vehicles are equipped with a drive battery that drives the motor, but in reality, they are also equipped with auxiliary batteries for operating electrical components such as headlights, navigation systems, audio equipment, and air conditioners. What is the role of the two batteries? Hybrid vehicles are equipped with nickel-metal hydride batteries and lithium-ion batteries, which are also used in mobile batteries, as batteries for drive motors under the floor. Toyota's new "Aqua", which was fully remodeled in July 2021, has succeeded in increasing driving in EV mode by installing a new battery with a large output called "bipolar type". In addition, there are "parallel method" and "series method" in the hybrid, and there are three types of methods called "series / parallel method" that combines both. The parallel system is a hybrid system in which the engine is the main power source and the power of the motor works as an auxiliary when starting from zero or accelerating. It is a type that is similar to a gasoline car. The series system is a system in which the engine is limited to power generation and the motor is the power source. The series-parallel system, which combines both of these properties, is a system that uses a motor for zero start and low-speed driving, an engine for normal driving, and both when power is required such as sudden acceleration. By the way, the "mild hybrid", which is often used in mini vehicles, can be said to be a system equipped with a "generator that has the function of a motor" rather than an electric motor that actively produces driving force. Recently, the "plug-in hybrid (PHEV)" has been attracting attention. It is a hybrid system equipped with a plug that enables charging from the outside, and is characterized by a relatively large capacity battery and a long mileage driven by a motor. Moreover, even if the battery power is used up for long-distance driving, you can continue to drive using the engine. Not only the drive battery that is involved in the basis of these hybrid systems, but also the 12V auxiliary battery installed in ordinary gasoline-powered vehicles to operate the hybrid system and electrical components such as headlights, navigation, and audio. It is installed. And when the auxiliary battery goes up, the hybrid car will not work, and it is necessary to connect a booster cable etc. and jump start like a normal gasoline engine car. Another thing to keep in mind with hybrid cars is that if the battery of another car runs out, you will not be able to turn to the rescue side of the jump start. Auxiliary batteries in hybrid vehicles have low power consumption and cannot generate electricity by starting the engine and operating the alternator like gasoline vehicles. In fact, the instruction manuals for hybrid vehicles such as Toyota clearly state that they cannot. In other words, you can get help, but you can't help other cars yourself. As the number of hybrid vehicles increases in the future, it cannot be said that there will be no situation where no one can help. It seems that it will be essential to have a mobile battery for cars that can jump start without a rescue car.