Newbie owner question

congrats and welcome!

1) half a tanker 'a few days' is meaningless. mpg = miles per gallon. reset trip a or b, fill the tank, drive until your down to 2 bars on the gauge and refill. divide gallons filled by miles driven to get mpg's.
then you'll know if something is wrong or not.

2) prius hybrid is a concert. there is no independent engine, battery or generator.
depending on conditions, the computers decide when the battery should be used for power or recharged, and when the engine is used for power and/or heat, or when it is off.

3) there's probably nothing wrong with your car, but it is 8 years old, and we don't know the history.
how many miles on it?

you have a lot to learn, and you've come to the right place. all the best!

 

Most of what I have said here has been covered in the threads by others on this website. If any member see's any errors, feel free to correct them.

The 12 volt battery, located in the trunk, is lower capacity than in most cars because it is not used to start the car. It just provides power to all the electronics. The hybrid battery, located under the back seat, is a 200 volt battery that provides the motive power.

There is no transmission as such in a hybrid. The internal combustion gasoline engine, ICE, is connected to a motor/generator, MG1. Electronics and road conditions determine whether it acts as a motor or a generator. The wheels are connected to a second motor/generator, MG2. There is no mechanical connection between the ICE/MG1 and the wheels/MG2.

The inverter is located under the hood. It charges the 12 volt battery. The throttle position, brake pedal position, SOC, engine temperature, vehicle speed and other conditions determines where the inverter directs the high voltage power.

To start the ICE, the inverter sends power from the hybrid battery to MG1 which acts as the starter motor. Once the ICE is running it spins MG1, acting as a generator, which provides power that can either charge the hybrid battery or provide power to MG2, acting as a motor, to move the vehicle.

The electronics/inverter tries to maintain the hybrid battery at about 60% charged so that if power is required from the battery, it is available but if braking is required, there is capacity in the battery to accept this electrical energy.

If the state of charge, SOC, of the hybrid battery is high enough and the temperature of the ICE is warm enough, a gentle accelleration at low speeds can be battery only for up to 2 miles. This is great for stop and go traffic. If a quicker accelleration is required or the hybrid battery SOC is low, the ICE will also start and assist in the accelleration. At freeway speeds, the ICE provides most of the motive power.

Braking: Depending on brake pedal pressure, the inverter determines how much MG2, acting as a generator, is used to charge the hybrid battery. Heavy brake pedal pressure causes the inverter to put a greater generator load on MG2 which slows the car more rapidly and it charges the hybrid battery at a higher rate. This regenerative braking saves the energy that is normally wasted as heat in mechanical brakes and instead that kinetic energy is converted to chemical energy in the hybrid battery. Generator loading is actually what slows the vehicle. The mechanical brakes only kick in below about 8 mph. Since regenerative braking is the primary braking means, the mechanical brakes should last 100,000 miles.

When coasting, MG2, acting as a generator, outputs a low charge. The inverter sends this current to the hybrid battery which gradually slows the vehicle down.

The Prius ICE is an Atkinson cycle engine. Most automotive engines are Otto cycle for maximum power. Two traits of Atkinson engines are that they provide less power for a given engine size but they have higher thermal efficiency (convert more energy from the gasoline to motive power) than an Otto engine. This makes sense for a hybrid vehicle where the Atkinson gives better mileage and the lower power of the ICE can be assisted by the hybrid battery when more power is required.

On most standard vehicles, the air conditioning, power steering and water pump are driven by a belt from the ICE. In order for the hybrid vehicle to travel at times without the ICE on, the air conditioning, power steering, water pump and power brakes were converted to run from individual electric motors. One advantage of this is the ICE can be off and the air conditioning will still function.

There is a second cooling system for the inverter and it has a reservoir under the hood, uses part of the radiator and also has an electric pump.

There are several temperature thresholds with the Prius. One is about 100 deg F. On a cold start in the morning, the ICE will run until that coolant temperature is exceeded and will not shut off when the vehicle is stopped. There is a second threshold at about 150 def F. Above that temperature the ICE will shut down when the vehicle stops. The third threshold is around 190 deg F. Above that, threshold, if the throttle is released at lower speeds, the ICE will shut off and it will remain shut down while coasting or if only light throttle pressure is re-applied.

It is a pretty amazing system.

 

Incredibly helpful post, thank you!

 

@john1701a has a great write-up on his website. Here's the link. John's Stuff - Toyota Prius User-Guide