I used to have a plug in hybrid electric car. It was great. For most trips, we burned no gas. On a typical day i would drive to the train station, and then drive home, maybe by way of the supermarket or the drug store. Then I’d plug it in. No gas.
But we burned gas for about half the miles we drove. We burned gas on long trips, or sometimes on intermediate ones. Like, if I drove into the city to visit friends, is get there on battery, but I’d drive home in gas (unless i could charge while i visited.)
The particular vehicle we had was a lemon, so we eventually gave up on it. But i loved the hybrid electric feature. We rarely had to buy gas. Basically, we only thought about it for trips. At first i worried that I’d get stuck somewhere because i never thought about it. But then i realized that every morning i started with plenty of power to get to a gas station.
Again, no. Hybrid electrical cars receive power both via mechanical coupling to the ICE and their electric motors. The simultaneous input is why they are called hybrid in the first place. They are mechanically able of moving with only ICE power, only electric power, and both at the same time.
Not if it’s a series hybrid. Does nobody read the other replies before commenting anymore? Hybrids are called hybrids because they use both gas engines and electric motors, not because of how they’re connected to the wheels.
I misspoke slightly. Pure series hybrid arrangements are not found in any production automobile I could find. They are technically called power-split or series-parallel, but often shortened to just “series”. They use various types of planetary gearset with multiple inputs to allow the ICE to drive the wheels directly when needed. The Prius is the prototypical example, and its use of a power-split device is well known:
As you may know, the Toyota Prius is fitted with an eCVT (electronic continuously variable transmission) unit that is using a single planetary differential gear set to combine power from two electric motors and a gasoline engine.
Regardless, I still maintain original point that diesel-electric locomotives cannot be compared to series hybrid vehicles as, in general, they do not contain batteries and cannot be internally powered without their diesel engines.
It’s a fast moving field. Diesel electric loco’s are now being fitted with batteries.
The battery-powered locomotive is the perfect complement to its diesel-electric brethren. The battery will hold 2,400 kilowatt-hours of energy, meaning it’s able to maintain full horsepower for roughly 30 minutes on a given charge. Then the operator can decide how to use that power.
Something similar is being used in the UK where a line has been converted to electric with an overhead pickup, but there is a tunnel that is too low for the power lines.
There are a few things happening. First, as I think some of the posts try to get at, hybrid cars are often also optimized for fuel efficiency. For example, the Toyota Prius and Honda Insight are small cars with small engines. Even if they were gas only, they would get good fuel economy. Hybrid systems are also offered in things like large SUVs that aren’t optimized for fuel economy. In those cases hybrids may help fuel economy, but it is going to be lower than for a car optimized for fuel efficiency.
Another thing that makes hybrids much more efficient is that electric motors are far more efficient than ICE. A larger percentage of the energy stored in a battery is converted to work, than the energy stored in gas or diesel fuel. So an electric drive system need less energy to do the same amount of work that an ICE system requires.
I’m sure I’m going to get my high school physics terms messed up here, so please correct me. Accelerating a car from 0 to 15 mph may require the same amount of work to be done whether the acceleration is due to internal combustion or electric propulsion. However, more energy needs to be released from gas (or diesel) than is released from the battery, because most of the energy released from the fuel is just wasted as heat, while most released from the battery is converted to useful work.
Conventional hybrids, that cannot be plugged in to fill the batteries, seem to top out in the 50 mpg range for combined. These are the small car ones, like the Prius or Ioniq. Plug in hybrids, where the battery can be charged and the car can run on electric only, have essentially unlimited mpg, depending on driving. A plug in hybrid with a 40 mile range that you drive 25 miles a day, and charge up every night? It would be easy to go thousands of miles (not all at once) without adding any gas.
I think you mean the Volt here. The Volt is a hybrid and they stopped producting it; the Bolt is pure EV. The i3 is actually a pure-EV with an optional range extending generator. But then there’s going to be an optional generator for the Ford F-150 electric pickup, too. Neither of these is normally considered a hybrid.
The i3, Volt, and (are there any?) others with an ICE generator are frequently referred to as hybrids by the press, dealers, and manufacturers. For example, a search for “hybrid” at CarMax will return the Volt. They are definitely better referred to as electric vehicles with ICE range extenders, as they are a different setup than something like a Prius Prime or BMW e car that are plug-in hybrids which can run in electric, ICE, or electric+ICE drive modes.
An idea which keeps surfacing from time to time is making your pure battery electric into a serial hybrid temporarily for long trips by dragging a gas generator on a small trailer behind it. When your battery starts going flat, you fire up the generator, plug the car into it, and continue on your merry way:
A few companies are updating that idea by using a trailer mounted fast charging lithium battery instead.
A rub with either idea is that many tiny pure battery electrics, like Bolts or Leafs, likely have warranties that will be voided if you tow anything.
I’ve been following the EV press fairly closely for a couple years now and can’t recall ever hearing the i3 being refered to as a hybrid. Perhaps I missed something. Or perhaps because the generator on the i3 is an option; without it, it’s a BEV.
I wasn’t arguing about the Volt; that’s always been called a hybrid.
There are a lot of features in hybrid vehicles to optimize their efficiency. To avoid confusion, it’s best to put plug-in hybrids in a separate category and just talk about non-plug-in hybrids, i.e. all of the energy ultimately comes from the fuel in the vehicle’s tank.
First, there’s aerodynamics. Don’t rustle the air, and you minimize your total power requirement in the first place. The preferred shape for hybrids these days hails back to the 1930s:
This has less effect at city speeds and more effect at highway speeds.
Second, there’ s the tires. Get the rolling resistance down.
Third, stop wasting energy on accessories. Instead of hydraulic assist for power steering (supplied by a pump that’s always spinning and moving hydraulic fluid whether you need it or not), use electric assist, which delivers energy only when you’re actually turning the steering wheel. Water pump? Decouple it from the crankshaft; make it electrically driven, and only spin it as fast as you need to to keep the engine cool.
Regenerative braking matters, too, but mostly in city driving where you tend to do a lot of stopping and starting. When you come to a stop, instead of pissing away all that precious kinetic energy as heat in the brake rotors, you pour a substantial fraction of it into the battery by using the electric drive motor as an alternator to make electrical power. When the traffic light turns green, the electric drive motor puts most of that energy back to the wheels, reducing the amount of gasoline you need to burn to get rolling again.
Finally, there’s the engine. People speak of the “compression ratio” and its relevance to efficiency, but really it’s the expansion ratio that matters. Most hybrids use an Atkinson cycle engine, which leaves the intake valve open well into the compression stroke. In doing so, the engine can effectively limit the maximum pressure/temperature near TDC, staving off troublesome knock/detonation while allowing for a very high expansion ratio that improves efficiency. Whereas a conventional modern Otto-cycle gasoline engine might have a compression ratio of 10:1, some of late-model Atkinson cycles are using as much as 13:1.
It was mentioned upthread that engines are more efficient at low RPM which brings up another aspect of hybrid drivetrain behavior. While it is true that lower-RPM operation (within reason) tends to be more efficient, this is a much lesser effect than increasing load, especially on throttled gasoline engines. Here’s an example of an efficiency map for a gasoline IC engine. RPM is the horizontal axis, load (torque output) is the vertical axis. The two-digit hyperbolic curves (10, 20, 30, 40, 50, 60 kW) are lines of constant power output, and the three-digit contours (17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 32.5, 35.0%) are lines of constant efficiency. Note that in most places on the map, if you want greater efficiency, you’d rather move up (toward higher load) than left (toward lower RPM). In a conventional drivetrain, shifting to a higher gear moves upward and leftward along one of those constant-power curves, achieving both. So one of the neat things about hybrid drivetrains is that they allow the vehicle to decouple the wheel load/speed from the engine load/speed, and they also decoupe the wheel power requirement from the engine power requirement. This means that the engine speed/load/power parameters can be trimmed toward a more efficient operating point than the vehicle speed/load/power requirement would dictate if a conventional drivetrain were being used. So for example, the IC engine might operate for a short time near its “island” of best efficiency (the “35.0%” contour on that plot I linked to), generating more power than the wheels need and stuffing the excess into the battery. When the battery is near full, the IC engine can slack off to something near idle and let the electric motor propel the vehicle forward. That near-idle condition is very inefficient, but the wasted energy is small in absolute terms, and the net effect of this sort of bimodal operation is an improvement in overall fuel economy.
And of course the last thing, already mentioned, is the ability to use a smaller engine with the expectation that the electric motor will provide a satisfactory assist during launches. The Prius for example uses an IC engine that maxes out at about 100 horsepower; my motorcycle makes more power than that. The Prius does fine for most driving situations, with the notable exception of climbing long steep grades in the mountains, where the battery and electric motor are kind of useless. I once drove a Prius up Pikes peak (14,000+ feet above sea level). By the time we reached the summit, that engine was gasping for breath and only making about 60 horsepower; it was not exactly a spirited ascent.
IIRC, the Kia Optima PHEV has a feature which periodically stirs the tank or runs the ICE to keep the gas from aging too much (settling? Congealing? Whatever it does that’s bad).
Internal combustion engines need to run at least a little bit every couple-three weeks to keep the parts lubricated and the battery charged. This is most likely what that car is doing.
Gasoline will go bad if left sitting for too long, but it’s usually something like a year or so. The lighter, more volatile fractions evaporate away and the rest turns to varnish. That’s potentially a problem for some of the more extreme cases of not needing the gas engine on a hybrid.
