Featured Why two-motor hybrid systems are better than those with just one

There reason for why the two motor is better is weak, and they even acknowledge that.
I was actually hoping for a more technical comparison, such as cost differences.

The reason we are seeing one motor, full strength parallel hybrids now is that the coordination of the system components was simply not possible when the Prius first came to market. The drive experience may not be flawless at this time, but so were blended regen and friction brake systems back in the day. This could improve in time for the hybrid system.

Then there are people that prefer shifting over CVT like driving. The article even had a negative to say about power-splits on that front.

 

i never bothered to consider GM's volt (gen 1 or 2) that much, over the years - but Bob's putting forth the 2 motor / 1 motor debate caused me to go looking - & this was what i found . . . . from the Volt's engineer - explaining the how & why's of 1 versus 2 motors.

i thought he made a good case - & stated it in a way that my simple mind could easily grasp.
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The Gen 1 Volt also worked in single and twin motor configurations, depending on the speed.

 

There are two motor-generators in the BMW i3-Rex. It just happens that one of them is always a generator (the one in the range extender).

kevin

 

From that aspect Mg1 doesn't always have to have any power going to it in the Prius.

I think the main distinction between the Toyota/Ford approach and the others is using a secondary motor instead of a changeable gear set - a series hybrid such as the i3 is closer to the series/parallel method than the single motor used in IMA or others.

kevin

 

To be fair, there's several levels of 2-mode system - the simplest form (as used in the Allison H40EP/EP40/H50EP/EP50, the Gen 2 Volt, and the current Malibu hybrid) isn't much more complex than a Prius transmission. The one used in the pickups, OTOH, had a lot going on.

In any case, really, the biggest problem with 1-motor systems boils down to the fact that it's hard for them to switch between engine off and engine on operation. The Honda IMA vehicles got around this by not even trying to propel the vehicle with the engine off - the engine has to be running to get propulsive force. And, the Ioniq actually is technically a 2-motor system, because it has a small motor/generator on the engine's accessory drive belt, primarily for starting the engine so it can rev match smoothly with the rest of the system.

 

The article's entire argument for a power-split being better than a parallel system is this, "We've concluded that single-motor systems simply get caught out more by sudden on-off acceleration: we haven't driven one that wasn't at least slightly lumpy or jerky at some point."

By that argument, friction only brakes on the brake pedal is better than having regen also controlled by it. This is a very subjective criteria in which to declare one better than the other. As I said, I was really hoping for something more substansive.