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The Volt has one propulsion system (electric engine) and two power sources (gas and battery). This is the principle of redundancy which is VERY DESIRABLE in all well-engineered systems. I am not sure what the exact fail-over mechanism is but if one fails (or runs out of energy - the more common case), the second should seamlessly take over. We know after 53 miles on battery, the gas engine will take over. We also know that running out of gas (in hold mode) will allow us to switch over to the battery for power.

We do not know if a fault in the battery (or the battery's electronics) or a catastrophic engine failure (i.e., the timing belt/chain breaking or the failure of the electronic ignition system) will allow us to run on the "backup" power source. An interesting question to investigate: how truly independent are these two power sources when it comes to making the car go based on different kinds of failure? A well designed and tested system would handle a variety of failure situations without leaving the driver stranded.

Unfortunately, redundant systems are expensive to design, build, and test. This may be why GM wants to go to BEVs - it is harder to make money with PHEVS. But they are great to own and use.

Volt owners are a fortunate lot even if the product is discontinued (way too early IMHO).
 

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The Volt has one propulsion system (electric engine) and two power sources (gas and battery).
The Volt's propulsion system is more complicated than that; the gas engine can be coupled to the drive wheels anytime the gas engine is running. The Volt's two electric motors can operate independently or together. Motor generator A (MGA), when coupled to the output of the gas engine, operates as a generator producing electricity to drive motor generator B (MGB). Guaranteed brain hurt here.
 

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The Volt's propulsion system is more complicated than that
I would agree with that, 100% - It's one of the most complicated drive systems on 4 wheels, especially for the Gen 2's

Don
 

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This is one of the reasons why I wanted a Volt over a Prime or a Clarity PHEV-- that if the engine died, I (at least theoretically) could drive 53 miles or so in an electric car.
 

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I would agree with that, 100% - It's one of the most complicated drive systems on 4 wheels, especially for the Gen 2's

Don
In terms of code running it? Maybe. In terms of mechanical complexity, I'd argue many modern automatic transmissions are more complicated... they have more gears and clutches etc than Volts do.
 

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Near as I can tell, MGA IS a motor/generator, but MGB only generates when driven by the wheels. Therefore we should call it a motor/regenerator. Correct me if this complexity has jangled my aging brain.....
 

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Discussion Starter #7
Correct me if I am wrong. I thought the gas engine NEVER drives the wheels directly. Only the electric motors drive the wheels. This is one thing that makes it different from the plugin Prius which uses its gas engine to provide additional power (to supplement the electric motor) via direct drive to the wheels.
 

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In terms of mechanical complexity, I'd argue many modern automatic transmissions are more complicated... they have more gears and clutches etc than Volts do.
True, many multi-speed automatics are indeed quite complicated . . . . but to my mind, few things beat coupling both an ICE and an electric motor to the axle at the same time and then controlling the speed of the vehicle not by how fast the ICE is running, but by regulating the speed of the electric motor - The combination of the two = the vehicle speed. They can even run the ICE fast and run the electric motor in reverse to get a slower speed. At least in the auto trans, everything's turning the same direction

Don
 

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Correct me if I am wrong. I thought the gas engine NEVER drives the wheels directly. Only the electric motors drive the wheels. This is one thing that makes it different from the plugin Prius which uses its gas engine to provide additional power (to supplement the electric motor) via direct drive to the wheels.
As mentioned a few posts above, when the ICE is running, it can actually be partially coupled to the wheels.
The volt remains completely different from traditional hybrids. Traditional hybrids are basically ICE cars with an electric engine to improve efficiency. The volt is an electric car with an ICE to provide electricity and sometimes improve efficiency.


If you search YouTube, you will find some good video explaining the Volt drive train in details. The Gen 1 and gen2 are slightly different, so check which video you are watching.
 

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Correct me if I am wrong. I thought the gas engine NEVER drives the wheels directly. Only the electric motors drive the wheels. This is one thing that makes it different from the plugin Prius which uses its gas engine to provide additional power (to supplement the electric motor) via direct drive to the wheels.
The part about the gas engine NEVER driving the wheels is closer to a true description of how the Gen 1 Volt operates (like a series hybrid in many/most driving situations.) The Gen 2 Volt operates as a parallel hybrid by design (when the gas engine is running, else it operates like a pure EV.) The Gen 2 Volt was specifically designed to couple the output of the gas engine to the drive wheels any time the Volt is using gas because it has been proven to be more efficient than turning mechanical energy (the gas engine's output tapped at the engine's drive shaft) into electrical energy (by way of MGA) to become mechanical energy (MGB electric motor output) to drive the wheels.
 

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The part about the gas engine NEVER driving the wheels is closer to a true description of how the Gen 1 Volt operates (like a series hybrid in many/most driving situations.) The Gen 2 Volt operates as a parallel hybrid by design. The Gen 2 Volt was specifically designed to couple the output of the gas engine to the drive wheels any time the Volt is using gas because it has been proven to be more efficient than turning mechanical energy (the gas engine's output tapped at the engine's drive shaft) into electrical energy (by way of MGA) to become mechanical energy (MGB electric motor output) to drive the wheels.
The plug-in Prius and Prius Prime, like the Honda Clarity PHEV, will spin up the gas engine if you fully depress the accelerator pedal. The Gen 1 and Gen 2 Volt will never start the gas engine unless the high voltage battery charge has been depleted or if the operator has placed the Volt into Hold Mode or Mountain Mode.
 

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The part about the gas engine NEVER driving the wheels is closer to a true description of how the Gen 1 Volt operates (like a series hybrid in many/most driving situations.) The Gen 2 Volt operates as a parallel hybrid by design. The Gen 2 Volt was specifically designed to couple the output of the gas engine to the drive wheels any time the Volt is using gas because it has been proven to be more efficient than turning mechanical energy (the gas engine's output tapped at the engine's drive shaft) into electrical energy (by way of MGA) to become mechanical energy (MGB electric motor output) to drive the wheels.
This may answer a question I was about to post. I was driving tonight under the following conditions and was surprised to see on the Energy Flow display that my ICE was sending power through the propulsion motor to the wheels:

ERDTT not deferred
Outside temp = 28 F
Coolant temp = 141 F
battery about 2/3 full
cabin climate control on eco, 74 F, and auto
heated seats and steering wheel on
going up a moderately steep hill.

As I said, I was surprised to see the engine adding some power when my battery was so full of charge. But I suppose my engine was running due to temperature < 32 F? And since the engine was running, the computer algorithms led it to contribute propulsion power? Amd I understanding that correctly?

PS: the Energy Flow display does not show a direct link from the ICE symbol to the wheel symbols; they are linked only through the electric motor symbol, which also serves as the visual link between the wheel symbols and the battery symbol. Perhaps this is artistic simplification?
 

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The part about the gas engine NEVER driving the wheels is closer to a true description of how the Gen 1 Volt operates (like a series hybrid in many/most driving situations.) The Gen 2 Volt operates as a parallel hybrid by design. The Gen 2 Volt was specifically designed to couple the output of the gas engine to the drive wheels any time the Volt is using gas because it has been proven to be more efficient than turning mechanical energy (the gas engine's output tapped at the engine's drive shaft) into electrical energy (by way of MGA) to become mechanical energy (MGB electric motor output) to drive the wheels.
More to the point, they flipped the transmission to be like other hybrids so that it could be used in other hybrids.

Just in time for gas prices to drop and hybrid sales along with them.
 

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This may answer a question I was about to post. I was driving tonight under the following conditions and was surprised to see on the Energy Flow display that my ICE was sending power through the propulsion motor to the wheels:

ERDTT not deferred
Outside temp = 28 F
Coolant temp = 141 F
battery about 2/3 full
cabin climate control on eco, 74 F, and auto
heated seats and steering wheel on
going up a moderately steep hill.

As I said, I was surprised to see the engine adding some power when my battery was so full of charge. But I suppose my engine was running due to temperature < 32 F? And since the engine was running, the computer algorithms led it to contribute propulsion power? Amd I understanding that correctly?

PS: the Energy Flow display does not show a direct link from the ICE symbol to the wheel symbols; they are linked only through the electric motor symbol, which also serves as the visual link between the wheel symbols and the battery symbol. Perhaps this is artistic simplification?
I have limited experience with ERDTT in my 2017 Volt as it just does not often get cold enough where I live in Maryland (<15F) for the deferred ERDTT to be activated. The few times that ERDTT has been active, starting with a cold engine and coolant ~32F (Volt is parked inside an unheated garage), the ICE will at first run continuously, not shutting down at traffic lights, until the engine coolant reaches somewhere between 150F and 160F. Then the ICE will cycle on and off as needed to maintain the engine coolant temperature between 120F and 140F. Perhaps the reason your Volt's ICE was running was that the engine coolant temperature had not yet reached 150F - 160F. Once it does get warm enough to produce cabin heat the ICE will run as needed to maintain engine coolant temperature sufficient to provide cabin heat. I can think of one other reason why the ICE would be running; perhaps the hood did not properly latch or the hood latch indicator switch needs adjusting.
 

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. . . . I can think of one other reason why the ICE would be running; perhaps the hood did not properly latch or the hood latch indicator switch needs adjusting.
Are you saying that if the hood is not latched (or is not perceived by the car's brain to be latched) the engine will run? That's interesting . . . and a little weird.
 

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The engine running when the hood is unlatched is for safety. You do not want the engine to start when someone has their hands on something on the engine and it suddenly starts. So before you can open the hood the engine is always running when the ignition switch is on.
 

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The engine running when the hood is unlatched is for safety. You do not want the engine to start when someone has their hands on something on the engine and it suddenly starts. So before you can open the hood the engine is always running when the ignition switch is on.
Interesting, thanks.
 

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There is anecdotal evidence of 1st gen Volts running fine with a disabled (for various reasons) ICE all over the WWW. 's why I bought one. Shame the ICE can't be removed entirely to make a lighter "around town" vehicle.
 

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There is anecdotal evidence of 1st gen Volts running fine with a disabled (for various reasons) ICE all over the WWW. 's why I bought one. Shame the ICE can't be removed entirely to make a lighter "around town" vehicle.
Used Spark EVs are about $10k, if that's what you really want. Probably get cash back from a trade for a Volt with even double the number of miles on it.
 

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I would agree with that, 100% - It's one of the most complicated drive systems on 4 wheels, especially for the Gen 2's

Don
Or least complicated, depending on whether you consider a traditional automatic transmission "drive" system or not and how complicated you're thinking THAT is. It could be argued that Prius style implementations are slightly less complicated than the Volt's, but .... there's advantages.

Copious Pile of Bookmarks has this in it. https://priuschat.com/threads/volt-drivetrain-patent-and-info.85572/ It's a (now charming and quaint) thread from a bunch of Prius nerds picking at the design of the Volt's system and comparing it to their own, and the whole thing breaking down to whether the posters think clutches are a good idea or not. From the benefit of 8+ of hindsight, that's not really been an issue.
 
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