Just some general questions about Hybrids. I’ve never owned one, nor driven one. I don’t necessarily see one in my near future, but I’m curious.
About how big is the battery pack? What does it weigh? Does it very greatly?
Where is the battery typically located? Is this starting to get standardized?
Why weren’t there plug in Hybrids from the very start? Was this a public perception problem? (oh my God, it’s a car that you “have” to plug in).
For decades, locomotives have used diesel engines to generate electricity for motors to pull the train. And use regenitive braking. I’m surprised that this is not the standard for long haul trucking.
I’m surprised that Hybrids use the ICE to give tractive power at all. Seems overly complicated. Wouldn’t it be best to just have the ICE charge batteries, and or feed power directly to the motor (for quick starts and acceleration).
Electric motor vs ICE. Which is more efficient when changing rpm’s? I think I read that an ICE is most efficient at idle, or top rpm. Wouldn’t it be best to set an ICE at it’s optimum performance, charge batteries and let the motor move the car? (that’s a tricky question, since you will also loose performance in energy storage and transfer).
I assume the Volt is using an ICE to recharge the batteries and always providing tractable power from the motor? Seems like a good idea to me. And less complicated, lighter weight.
A long-haul truck spends most of its time moving at a nearly constant speed with little to no braking. This would appear to be the regime where a hybrid system would have the least to offer.
It should be noted that if there are significant hills along the truck’s route, a hybrid’s ability to store energy on the downslope and expend it upslope could be useful. This would need to be set against the presumed extra weight, cost and complexity of the hybrid propulsion system.
The Prius’s battery is basically under the rear seat. (goes back a bit).
This makes it so you can fold the rear seats and have quite a bit of room.
There is a small compartment below that (I keep a decent size tool kit there).
Below that is the tire storage and in front of that is the main battery (There is also a small 12v battery that basicaly keeps the computer alive - it is in the left rear of the car)
Toyota says that optimal life of teh battery is if it is kept between 20-80%* charge. Plugging in would charge it 100%.
I can’t answer all of your questions, but I can answer some of them from a more theoretical perspective.
For there to be any value in plugging in, the battery pack has to be large enough to store a reasonable amount of power. From what I understand, the Prius (for example) can travel less than a mile on battery power alone. (citey-cite) Why bother plugging in to go one mile? You could, of course, increase battery pack size or decrease the car weight, but that leads to other compromises in cost, efficiency, and reliability. A plug-in is by no means a dumb idea, but with all the trade-offs it’s not a slam-dunk either.
I’m not. First of all, I’m going to dispute the claim that locomotives use regenerative braking. I’m not a railroad expert, but Wikipedia says, “Dynamic brakes (“rheostatic brakes” in the UK), unlike regenerative brakes, dissipate the electric energy as heat by passing the current through large banks of variable resistors. Vehicles that use dynamic brakes include forklifts, Diesel-electric locomotives and streetcars.” Also, from here: “Due to high average weights of freight trains and the fact that only locomotive axles are powered, high shares of braking power comes from the mechanical brakes in the freight cars, and only a small share is added by the locomotive itself. Based on conventional freight trains, there exists limited potential to raise the share of recovered braking energy.”
But that’s not a critical component of your question. As Xema notes, the long-haul truck spends a lot of time at highway speeds, where the engine operates near peak power and best efficiency. Hybrids increase efficiency by, primarily, managing the engine to operate at a more efficient point than it would otherwise; and secondarily by recapturing braking energy. There’s not much room for efficiency increase on either point in a long-haul truck driving cycle; I wouldn’t be surprised if hybridizing such a truck would decrease overall fuel economy.
Finally, note that for diesel-electric locomotives, "the main reason why diesel locomotives are hybrid is because this eliminates the need for a mechanical transmission, as found in cars. " (from here)
As you say, you’re talking about the difference between parallel and series hybrids here. There are three possible reasons I can think of for this. The first one is that, practically, different driving cycles favor either the series or the parallel hybrid. I suspect most passenger vehicle driving cycles would do better with a series, but that’s not cut-and-dried.
The second (which is coupled with the first reason) is that a series structure requires all engine power to flow through the electric portion of the drivetrain. That means you need large motors, large generators, large batteries, large cables…everything’s upsized. The series might give better efficiency overall, but it’s likely to be heavier and more costly.
Finally, there’s customer acceptance and reliability. Hybrids are probably mature enough now that this isn’t so much of a concern, but ask yourself: what would happen if the electric system took a dump? In a parallel hybrid, you shut down the electrics, drive home, and get it fixed later. With a series, you need a tow.
Again, a parallel V. series question. First of all, the ICE is most efficient at high torque and generally mid-range rpm (idle, by definition, is 0% efficient). Electric motors tend to be similar, but the efficiency curve is much “flatter”; i.e., it can be operated over a wider range without a substantial rolloff in efficiency.
Second of all, remember that batteries are not 100% efficient; in fact, their efficiency can be downright terrible when you’re running high power. However, in many circumstances, the efficiency advantage of running the ICE at its peak efficiency will outway the downstream losses from motor and battery, and thus the series configuration will win out.
My sense is that, for most applications, the series configuration would win out, but this is most certainly not a trivial decision even from a max efficiency standpoint. It’s even more complicated when you add in weight, cost, and reliability requirement into the equation.