I was always under the impression that all hybrids were basically an ICE driveline, with a conventional transmission and driveline, with an electric motor piggybacked in parallel. A while back I started studying Toyota's "Hybrid Synergy Drive". As you said, it's a pretty fascinating system, with a motor/generator coupled to the system, utilizing the motor somewhat like a torque converter/clutch when in "ICE mode". Pretty interesting approach, and far less mechanical mechanism than I realized. From everything I've read they are one of the most reliable and long lasting vehicles available. I need to learn more about their PHEV version. Not looking to buying one necessarily, but I find the engineering interesting.
Minor additional comment, then this all has to disappear off the investors' forum.
The magic in a Prius is in this planetary gear set. Three things are connected: A shaft, hitting the gears in the center; an electric motor, connected to (I think) a ring attached to the planetary gears; and the ICE, which is directly connected to a ring hitting the outside of the planetary gears. The other end of that shaft goes into the second motor and is directly hooked into (fixed) gears that drive the front wheels.
The ICE can run without the car actually moving (charging the battery.. or not); the ICE can be off while the motor generators drive the car forward or in reverse; and any of the above, at any time. There's even use cases when going downhill at 65 mph where the motor-generators spin the ICE with the valves closed and the ignition off, in order to keep the motor-generators from overspeeding
. There
is a small clutch plate between the ICE and the planetary gear set, but its only purpose is to provide a bit of slippage if the ICE stops or starts abruptly; one can't disengage that clutch, it's fixed.
But the motor-generators in the Prius have enough torque in them to flip a person the length of a football field or something. When Toyota wants to start the engine, they literally
spin the ICE with the motors before applying spark and gas. So, if one is traveling in a straight line at a steady speed or slowing down, the car will
stop the ICE and run on motor generators alone. And turn the ICE back on when needed for acceleration or keeping the battery from getting too low. Seriously, a driver
rarely even notices the engine starting and stopping; software control of the motor-generators does this activity very smoothly. Note that not all hybrids are like this, although some approach it.
The Atkinson ICE is part of the fun. Atkinson's get 20%+ better efficiency or something converting gasoline to kinetic energy and (CO2+H2O) than a normal Otto-cycle ICE. That's how Priuses pull off getting 50 mpg chugging down an interstate at 65 mph. And why other Toyotas with Synergy drive (Camry's, what-all) get similarly good numbers.
In the realm of silly party tricks, there are Prius owners who connect up a relatively high power 12V to 120 VAC inverter to the car's 12V battery and use it during city power outages, with the car on. The car's main traction battery goes from (I think) 300V down to 12 through an efficient inverter, keeping the 12V battery charged; when the traction battery gets low enough, the car starts the ICE and charges the traction battery back up, then turns the ICE off; lather, rinse, repeat. I think I did the calculations once upon a time and the car's a more efficient source of 120 VAC by a factor of two or something to a Home Depot gas-fired electric generator. Albeit that there are limits; I think I figured I could run the hot water heater and house refrigerator that way, but not much else.
All well and good: But the Tesla is
still cheaper to run, at least if one is charging at home or with solar (both true in my case); in terms of straight cash to go down the road, a Tesla with Superchargers and a gas-fired Prius are about the same. Except - the Prius still needs oil changes every 10,000 miles. And a Prius doesn't have as much internal storage as the M3 daily driver I chug around with over here. Back seats in the Prius are more comfortable than M3 back seats, too, I guess.
In the end, though, Priuses simply aren't as good for the environment as a BEV: Make no mistake, that's gasoline in, carbon dioxide out, just like every other ICE out there. A PHEV is
marginally better, so long as one charges it. But it's still emitting CO2.