Toyota Prius - Gas/Electric Hybrid

In the spring of 2001 Karen and I purchased a new car, a Toyota Prius. This car is very special because it is a gas/electric hybrid. The gasoline engine powers both the wheels and charges the high voltage battery. It runs at the most efficient rpm as determined by the computer and produces about 10% of the emisssions of the cleanest gas engine. It is rated as a SULEV, Super Ultra Low Emissions Vehicle. Power also comes from an electric motor fed by the high voltage battery. The continuously variable transmission delivers the smoothest ride I've every experienced. The result is an extremely quiet ride and 45-50 mpg to boot. You never plug the car in, as the batteries are recharged by the internal combustion engine. THE FUTURE IS HERE FOLKS!

Karen and I have been on the web as part of a PBS presentation on hybrid vehicles. Take a look at This was about 10 years ago. In 2011 we traded in the 2001 Prius for a brand new Prius 3. This car retains the original drive concept but is an intermediate size rather than a compact. Our car has all the bells and whistles with built in NAV, bluetooth to connect your cell phones for hands free talking, and an upgraded sound system.

The first thing you need to know is the concept of Conservation of Energy, which states that in transforming energy from one form to another, energy is always conserved. Energy is never created or destroyed. This means that if you convert chemical energy (gasoline) into motion energy (car moving) you can NOT get more motion energy out than was put in.

The second thing you need to know is that any energy transformation is never 100% efficient. For example when you convert chemical energy (gasoline) into motion, some of the energy becomes heat (put your hand near the warm engine or hot exhaust pipe-actually be careful or you’ll burn yourself.) Heat is another form of energy that is part of the total transformation but it is not the motion of the car which we desire. Another example of transformation in an automobile is braking. If takes energy to stop the motion of a car. When you apply the brakes, the motion is transformed into heat and sound energy and the motion of small bits of the brake shoes as the car stops.

The Prius does a number of wonderful things to make better use of the chemical energy in the gasoline. At a red light, the engine (when warm) shuts off. Since the car is not moving, there is no need to run the engine and use gasoline when no motion is called for. For a regular car, this is impossible since the power to start a regular engine often in city driving would deplete the 12V battery and the process is too slow for most people. The Prius spins of the engine up to 1000 rpm using one of its electric motor/generators with the valves open and no ignition. This means it takes relatively little energy to smoothly and quickly start the car.

During light braking, the motion energy is used to turn a motor/generator which produces a drag and electricity that is stored in a battery for later use. Heavy braking engages the brake pads which convert the rest of the energy into heat, etc. For clarification, a motor and a generator are the same thing. If you put electricity in, you get motion out. If you put motion in, you get electricity out.

There are several other innovations that increase efficiency. They include the Atkinson cycle engine and the Power Split Device (transmission). Because there are no traditional gears in the Power Spit Device, the result is a continuous variable transmission. There is no shifting of gears, only smooth acceleration as the computer controls the gasoline engine and whether the motor/generators produce motion or electricity. How these features work is really in the realm of the engineer. If you go to Graham Davies website, you can find a clear but complicated discussion of these features -

Storing your car more than 3 weeks

A number of people have raised the question of long term storage and its effects on the 12V and HV (High Voltage) batteries in the car. I have had some direct experience in this area. Our car has been left in an airport parking lot for 14 days with no problems. Nothing was done except to park and lock her. Because of our bicoastal life, we leave the car for extended periods. Under this circumstance I disconnect the 12V battery and leave the car in the garage. She has been left for as long as 100 days with no loss of HV energy as indicated by the battery icon. In all cases of a lengthy storage, there were no problems starting the car after the 12V battery was reconnected. You will have to reset the clock and radio settings, however.

12 Volt Battery replacement

In Sept. of 2008, the 12V battery began to fail in our 2001 Prius. After consultation with the gurus on the Yahoo Prius discussion site, I purchased and installed an Odyssey PC680. This is a drycell type battery, much smaller than the original 12V battery and came highly recommended. The battery began to fail after 10 months. Although under waranty, they would not honor it unless I sent the battery to their factory for testing. As a one car family this was impossible. The alternative was to purchase a new Odyssey battery, send the old one in for testing, and if verified, they would credit my purchase. Not wanting to be burned twice, I opted to purchase a Miata battery. This required no modification of the battery holder, was more powerful than the new Prius battery, and was substantially cheaper. It cost $127 while the new Prius battery with the modification of the battery holder was about $300. I expect a similar situation with our 2011 Prius.