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Question I couldn't answer about hybrids.
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01-11-2009, 10:00 PM
I am telling my son that the lead acid batteries we were standing next to could be used to power hybrids. I said they are charged by a regular engine then electric motors drive the car. He asks why does it take less energy to charge the batteries by burning gas then have motors drive the car rather than just let the gas engine drive the car? I really didn't know why.
01-11-2009, 10:06 PM
The term you need to learn more about is regenerative braking.
http://www.google.com/search?hl=en&q=regenerative+braking The batteries are not charged by the gasoline engine only, they are also charged by the car slowing down. Also, in hybrids like the Prius, both the gas and electric motors can drive the wheels, so you don't convert gas to electric to motion. Gas can go directly to motion. Edit: Hybrids work by capturing normally wasted energy and storing it in a battery and using that energy to assist (and at times replace) the the power from the gas engine.
01-11-2009, 10:10 PM
Furthermore, perhaps one of the biggest reasons for using the electric motor is that it allows you to use a smaller engine that runs at optimum speed. Most car engines are sized for acceleration. But once the car has accelerated to cruising speeds, it only uses a small percentage of it's overall power capability. All engines have an optimum running speed and size for a given power requirement. Perhaps others can fill in with more detail as my answer is very general.
01-11-2009, 10:13 PM
I am looking for the source of that "extra" energy. So braking is it? If you take away breaking, is it an even trade?
01-11-2009, 10:20 PM
like Carnos Jax mentioned, you can get a smaller engine to run at a constant speed and be much more efficient that a regular engine.
Today's hybrids work like GGD described, the gas engine drives the wheels and also charges the battery, and when you brake, or go downhill, the battery is also charged, even if the gas engine is off. Chevy Volt (if we ever get to see it), it's supposed to have an all electric drive train. You plug it in, charge the batteries, and can go up to 40 miles. Then, if you run low on the batteries, a small gas engine kicks in and runs at constant speed to charge the battery, but it will not drive the wheels. So if you speed up or slow down, the gas engine doesn't care, it runs at optimum speed until the battery is full and then it stops again. The drive train is all electric. I am curious what the MPG is for chevy Volt when you take a long trip and run mostly on gasoline. I think GM CEO went from Detroit to DC n a Volt the second time to ask for $$$.
01-11-2009, 10:22 PM
Dakota wrote: hard to say, you could recharge the battery when you go downhill (even if you don't actively push the brake pedal). Also, the PRIUS is designed from ground up with efficiency in mind, unlike a GM car.
01-11-2009, 10:23 PM
Dakota wrote:Start here, read, learn.: http://auto.howstuffworks.com/hybrid-car.htm Also, it is "braking", not "breaking". BGnR
01-11-2009, 10:34 PM
cars are slowly becoming more like diesel electric locomotives.
01-11-2009, 10:35 PM
BigGuynRusty wrote:Start here, read, learn.: http://auto.howstuffworks.com/hybrid-car.htm Also, it is "braking", not "breaking". BGnR You just can't hide that mean side of yours, can you? What is it? Bringing your frustrations here from the other side? Have I roughed you up that bad?
01-11-2009, 10:39 PM
Dakota wrote: They also save by not idling the gas engine, it can be shut off. Coasting and going down hill get the best mileage, the gas engine can shut off, and the battery can charge down hill even if you're not braking. At stop lights, the engine can shut off, and the electric engine gets used when the light turns green, and the gas engine can then start up while you're already moving if needed. I don't know if you can really measure if it's "an even trade" because the car doesn't operate that way, it will use the gas engine to directly power the wheels when that's the most efficient thing to do (it also charges the battery as it's powering the wheels). There is a lot of computer control that decides when to use the gas engine. I think about the only way to get the gas engine to come on just to charge the battery without also moving the wheels is to have the car stopped with the air conditioner (all electric) running for a very long period of time. One limitation that I run into is the size of the battery, from my house there is a 3 mile down-hill stretch, and the regenerative braking will fully charge the battery before I reach the bottom, so that time from when the battery is full, until I get to the bottom, I'm generating energy, but there's no place to store it, so it's being wasted. (I'm referring to the way the Prius works above, because that's what I own and understand best). |
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