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Odd Things About Hybrid Cars

I'm speaking here of the first generation Prius and Ford Fusion Hybrids among others. Different brands of hybrids can be different.

I'd always thought of hybrid cars as cars with an electric motor and big battery attached to the engine. But hybrid cars of this type are way different.

One odd thing about a hybrid car is that when you start it the engine doesn't come on. It turns on later when needed. Lights flash and an indicator tells you when the car is ready to drive.

Another odd thing about the hybrid transmission is that there are no gears in the sense of gears that change gear ratios. Instead there is a differential. You are no doubt familiar with how a differential works. A differential in the rear axel of a rear wheel drive car enables the wheels to vary their speeds inversely so that if one wheel is turning at 300 rpm the other is going 700 rpm, or if one is going 200 rmp the other is going 800 rmp, if one is going 0 rmp the other is going 1000 rmp. The speed of the two wheels added together equals the speed of the drive shaft.

Now imagine instead of wheels the differential is connected to two electric motors both of which can also act as generators. They are AC motors so their speeds can be controlled precisely. We can call one of them MS and the other MT. In this example the drive shaft would be connected directly to the engine and MT is also connected to the output so that it's in line with the transmission output shaft.

220px-THS_evol_1.pngMG1 = MS in my discussion, MG2 = MT. The differential in the center is a planetary gear with S = sun gear, C = carrier, and R = ring. ICE = internal combusition engine. From Wikipedia.

Now, you step on the gas. The computer determines that the electric motors won't provide enough power for your jackrabbit start, and so the engine comes on and spins up to 1000 rmp. With the car stopped MT is at 0 rmp so MS is spinning at 1000 rmp, and it's generating electricity which can be used to charge the battery. That electricity is then fed to MT to provide torque. As the car speeds up MT spins faster and MS slows down. And so you go from high torque low speed on the output to high speed low torque just as changing gears in a standard transmission would do. Only no gears are being changed, its done electronically by controlling motor speeds. The engine provides mechanical power, too, that is blended with that of MT.

There is no reverse gear, either. Reverse drive is done by reversing the polarity of MT. Braking is done in part by tapping electricity from MT. The electricity is stored in a battery for times when the car can be run with the engine stopped.

There is no starter motor in a hybrid car. Instead one of the electric motors in the transmission is used to turn the engine. The engine turns off and on several times over the course of a commute to work.

The only difference between a regular hybrid and a plug in hybrid is the battery capacity, which is much higher in a plug in hybrid. A regular hybrid can only go a couple of miles on a charge while the higher capacity of the plug in hybrid enables it to go several miles, perhaps avoiding the need to run the engine at all. Hence charging it by pluggin it in.

Later versions of the Prius and Lexus hybrids have gears, a single gear ratio change from low to high on the output (drive shaft) which enables the transmission to run at lower revs and therefore more efficiently.
 

longview

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Thank you for the description, I knew the early hybrids we not series hybrids, but never heard how they actually accomplished it.
I have always thought the best utilization for hybrid tech would be a large Pickup/SUV.
DC traction motors on each wheel, with the battery pack over the rear axle.
A small ICE motor to keep the batteries topped off.
If you need to pull something heavy, traction motors are the way to go,
100% torque from a dead stop.
It would also reduce fuel consumption more.
Joe environmentalist swaps out his Toyota Corolla at 35 mpg for a Prius at 45 mpg.
Saves 77 gallons of gas in a year.
Bob's F250 gets 15 mpg, swaps for a 30 mpg hybrid truck.
Saves 400 gallons of gas in a year.
A good hybrid truck would have almost 5X the impact of a Prius.
 

ttwtt78640

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The basic problem that I see with all hybrids is that you always have the added dead cargo weight of the alternate vehicle propulsion system. While acting as an electric car, you must haul the added dead weight of the FF supply and the ICE engine, while acting as an ICE car, you must haul the added dead weight of the batteries and the electric motor(s). The increase in the initial vehilce cost, plus the added complexity/maintanence of having two different drive systems does not offset the operational cost gains unless you discount the cost of outside electricity generation or add a gov't subsidy. If these hybrids were truely as cost effective, as they are advertised to be, then they would take over the market on their own merit rather quickly.
 

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In a serial hybrid, the ICE engine gets much smaller, and the transmission goes away.
Look at the wheel motors used in this prototype car.
A Plug-In Hybrid For $3,000? Thank These College Folk For That | Earthtechling
I agree that when the price point and value lines of the hybrid cars cross,
people will buy a lot of them.
I think the hybrids will have a big market with the performance car people.
If you got everything balanced correctly, 4 traction motors could require a trip to the
chiropractor after a hard acceleration:).
 
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