In addition to a heavy-duty starter, start-stop systems require such components as enhanced engine control, battery management, DC/DC converters, and more robust crankshaft sensors.
(Source: Robert Bosch LLC)
I had the clutch go out in the K2500 camper while returnin home from a cross country trip. I would turn the engine off when coming to a stop. I had the 5 speed in 1st and would crank when the light turned green. I would use the clutch to shift but it would not through out enough for a stop. 5 speed fully syncromesth manual transmission. Preplaced the clutch and hydraulics but the starter is still going strong. I can shift up pretty good without the clutch but down shifting is a challange to match speeds.
My Dad had a gas - electric golf cart. Push on the go button and off she goes and seamlessly starts the gas motor. No felt changes but you would hear the gas engine start. Pretty quiet too. I see no problems other than realy needing a higher voltage system, 48v or more.
I agree that an integrated starter/alternator seems preferable to simply modifying the existing Kettering starter for more durability. Combining two components into one eliminates the weight of a seperate starter assembly, saving between 5 and 10 pounds. In addition, eliminating the belt drive in favor of direct-drive would eliminate the belt slippage and breakage that is still a problem, although less so than in the past with the adoption of "serpintine-belt" systems replacing traditional accessory-drive belts.
This is part of a general trend to replace mechanical accessory drives with electrical substitutes. First, the direct driven engine cooling fan was replaced with an electric motor. Then electric power steering began to replace engine-driven hydraulic power assist. With an integrated starter-alternator, the belt-driven alternator disappears. Eventually, even the internal combustion engine itself may disappear, although it is still not entirely clear what the final replacement for it will be.
The most important point is to look at the problem from a systems point of view, rather than focusing solely on the starting problem. Can we replace water pump and air-conditioning belt drives with electric motors, to allow operation during stopped mode? What demands will this place on the battery (or batteries)? Does a larger battery or additional motors offset the weight savings elsewhere in the system? Should we convert the air-conditioner to a heat pump, to allow for cabin heating before the engine warms up? A systems approach allows us to answer all of these questions and many more, so that we don't create more problems than we solve. It also encourages innovation and "out-of-the-box" approaches, such as sensing which cylinder is on the expansion stroke when the engine turns off, so that you can re-start the engine by injecting fresh fuel and firing the spark plug for re-start, rather than using the starter motor at all (as outlined in a recent Mazda patent).
Maybe I missed it, but it seems like there should be a clutch on the flywheel and a way to keep the flywheel spinning for restart energy (this energy would be almost free.). Seem like a lot of energy is lost stopping and starting the flywheel.
The Prius has had this on/off technology for a dozen years or so. I have had mine for eight years, with no problems. The "starter" uses the two HV electric motor/generators to kick the engine over. It starts in less than a revolution. Fuel is not fed to the cylinders until sufficient revolution rate is sensed. The car uses electric A/C, so that it will run with the engine off. If the traction battery runs down due to its load, the engine will start to re-charge. BTW, the electric motor in the A/C allows it to be a sealed system, similar to a window A/C, so no service should ever be required. The engine also runs continuously during warmup in order to heat the catalytic converter. The engine shuts off when you let up on the accelerator up to around 42 mph. The only reason for that speed limitation is to limit the rotational speed of one of the motor/generators to its rated maximum of around 10,000 RPM. All of these functions are controlled by the on-board computers.
So please don't wring your hands about how awful it will be to implement start/stop. It has been around and working well for many years, and appears to me to be the best near-term solution to gasoline consumption reduction. My gasoline mileage, averaged over my entire eight years of ownership, is a little over 50 mpg. It does poorer than that in the winter, and better than that in the summer. The difference is mainly due to increased warm-up time in cold weather.
Good story about eAssist, Rick. One of the beauties of this system is the relative small size of the luthium-ion battery (0.5 kWh). Compare that to the Volt (16 kWh) and the Prius PHV (5.2 kWh), then compare the cost savings. Assuming these batteries cost $1,000/kWh, as the National Academy of Engineering has said, that's a savings of multiple thousands of dollars. True, it's not a full hybrid system like the kind you'd get in a Prius, but it's an inexpensive way to get SOME of the hybrid features.
One other concern, which is probably the one that will kill the versions with the very greatest efficiency, is what the NTSA people will conclude about how safe the start stop system will be. My guess is that engine shutoff at traffic lights is all that they will allow. After all, these are the same poorly advised folks who allowed cars to be sold that did not have a positive means to switch off the engine. That piece of stupidity has cost a few lives and a fair amount of property damage so far, and I am not aware of any changes to the functionality of that system that would make it any less dangerous.
I agree about the air conditioning. I don't like using it in the car unless I have passengers who want it. My issue with AC is a holdover from the 30 years ago, when I used to have to nervously watch the engine coolant temperature gauge in my '77 Cutlass whenever I turned on the air conditioning.
Electric power steering should not require an additional battery since mostly drivers are not turning the car, and most coasting is done in a fairly straight line. Besides that, there is very little steering done when the car is stopped.
As for the air conditioning, shut it off while coasting! 50% on time should be plenty cool enough, those drivers who can't live without an icey blast 100% of the time are folks that I really don't care at all to accomodate. Really, I don't care. Of course, cars could have better insulation, for example, urethane foam like refrigerated trucks have. That would also make the ride quieter and not add over a pound to the car's weight. It might even make the car stronger.
Another option would be to allow those drivers who must hold 65 degrees to keep the engine running, and let the rest of us save the fuel costs. Then there would be no room to complain for them at all.
Power brakes might be a different story, because although I have seen hydraulic-assisted power brakes, those systems used the power steering pressure, which is gone with electric power steering. Of course, for many years power brakes were an option, they may still be, I am not sure. I do know that my first two cars did not have them, and neither did the race car that I drove for a few minutes once. So dispensing with them altigather is another option.
I think you've nailed it, William K, when you say that air conditioing and other accessories will be a challenge. For AC, automakers atalking about adding a temperature sensor that could look at ambient air and enable the vehicle to decide if the engine should be turned on again. Regarding steering: If it's electric steering, an extra battery would be needed for coasting.