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I see conflicting answers on this question. Some say that when you run out of battery (and driving in normal mode), the gas engine charges the battery, which drives the wheels. Others say the gas engine drives the wheels directly without charging the battery.

Does anyone know for sure?

This is important because if it's the latter, the battery is basically untouched (and thus will have longer life) when in gasoline engine mode.
 

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I see conflicting answers on this question. Some say that when you run out of battery (and driving in normal mode), the gas engine charges the battery, which drives the wheels. Others say the gas engine drives the wheels directly without charging the battery.

Does anyone know for sure?

This is important because if it's the latter, the battery is basically untouched (and thus will have longer life) when in gasoline engine mode.
Both - and neither. The ICE never drives the wheels directly, as GM said any number of times. Key word: directly.

At speeds over 35 mph with the engine on the ICE is driving the wheels mechanically, through the clutches and MG A shaft and the planetary gearset in a fashion that's basically the same as a Prius (but different in details.)

Below that speed (or under hard acceleration,) the engine isn't connected to the wheels - it turns MG A, which generates power, which MG B turns into torque again to drive the wheels.

Under either scenario, the car is charging or discharging the battery as needed to achieve the desired performance efficiently in a fashion typical of a hybrid car.
 

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Watch your power flow indicator below the speedometer. That shows you what the power source condition is at all times. Watch it in hold mode or watch what happens if you engage MM once you've run out of Normal battery.

The engine revs at higher rpm to replenish the battery level over what it takes to sustain your driving speed requirements. The battery is never empty. There is always a small reserve for quick burst acceleration.


Sent from my iPhone using Tapatalk
 

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Both - and neither. The ICE never drives the wheels directly, as GM said any number of times. Key word: directly.

At speeds over 35 mph with the engine on the ICE is driving the wheels mechanically, through the clutches and MG A shaft and the planetary gearset in a fashion that's basically the same as a Prius (but different in details.)

Below that speed (or under hard acceleration,) the engine isn't connected to the wheels - it turns MG A, which generates power, which MG B turns into torque again to drive the wheels.

Under either scenario, the car is charging or discharging the battery as needed to achieve the desired performance efficiently in a fashion typical of a hybrid car.
You have to be careful about which GEN you are talking about. Gen 1 had the ICE function mainly as a generator except in some circumstances (my preference BTW). Here is a quote:

"The Volt’s powertrain configuration [for GEN 2] has changed significantly. It now uses its smaller, more efficient 1.5-liter gasoline engine mostly to power the car while it’s operating as a hybrid, rather than to charge its battery. In past Volt models, the engine would only connect to the wheels in the most demanding situations and otherwise be used strictly to charge the battery while the motors did the driving. A new twin planetary gearset—replacing a single—allows for more versatility in how the engine, motors, battery and regenerative brakes can be optimized to meet different driving demands. Maximizing efficiency is the name of the game."
 

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You have to be careful about which GEN you are talking about. Gen 1 had the ICE function mainly as a generator except in some circumstances (my preference BTW). Here is a quote:

"The Volt’s powertrain configuration [for GEN 2] has changed significantly. It now uses its smaller, more efficient 1.5-liter gasoline engine mostly to power the car while it’s operating as a hybrid, rather than to charge its battery. In past Volt models, the engine would only connect to the wheels in the most demanding situations and otherwise be used strictly to charge the battery while the motors did the driving. A new twin planetary gearset—replacing a single—allows for more versatility in how the engine, motors, battery and regenerative brakes can be optimized to meet different driving demands. Maximizing efficiency is the name of the game."
The generations are different, true. I presumed that the OP had deliberately chosen to ask this in the Gen 1 forum, and I tailored the answer to match.

Note that your quote is incorrect - it's actually the other way around. The engine connects to the wheels in everything except the really demanding situations, as long as you're above the speed threshold.
 

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The generations are different, true. I presumed that the OP had deliberately chosen to ask this in the Gen 1 forum, and I tailored the answer to match.

Note that your quote is incorrect - it's actually the other way around. The engine connects to the wheels in everything except the really demanding situations, as long as you're above the speed threshold.
It seems your answer was more for Gen 2. My understanding is that the ICE is not used directly until speeds greater than 55-60 MPH.
 

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It seems your answer was more for Gen 2. My understanding is that the ICE is not used directly until speeds greater than 55-60 MPH.
Your understanding is incorrect. Unless you're accelerating hard, the car will start the transition to Power Split at 36 mph, and once in Power Split, it will stay there all the way down to 30 mph.

55-60 is about where it switches from single motor EV to 2 motor EV, though, so possibly that lead to the misunderstanding. It's a throughly complex little beast...
 

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Just drive and don't worry about it. The car's computers have it all under control.

For the most part, the ice drives the generator which drives the electric motor which drives the wheels, but there are multiple modes where the ice participates in pushing for both gen1 and gen2.
 

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Discussion Starter · #11 ·
Thanks and yes I have Gen 1. So it seems that driving the volt with zero battery power (and thus ICE) still charges and drains and thus ages the battery.

So a volt that's only been driven on ICE for 100,000 miles won't have any better of a battery than a volt that's been driven electric for 100,000 miles, I guess.
 

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Thanks and yes I have Gen 1. So it seems that driving the volt with zero battery power (and thus ICE) still charges and drains and thus ages the battery.

So a volt that's only been driven on ICE for 100,000 miles won't have any better of a battery than a volt that's been driven electric for 100,000 miles, I guess.
The Volt never fully charges or discharges the pack, and cycles near the middle have relatively small effects on longevity anyway.

The car driver on the ICE for 100k will have passed maybe thirty percent of the energy through the pack that the car driven electrically did. Remember, just because the car is generating electricity and using that to drive the motor doesn't mean the pack is cycling - the pack only sees the net difference between the power used and the power generated. Under most driving condition with the ICE on, the engine is producing more or less the amount of power needed to move the car, with only a small balance to/from the pack.
 

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The Volt never fully charges or discharges the pack, and cycles near the middle have relatively small effects on longevity anyway.

The car driver on the ICE for 100k will have passed maybe thirty percent of the energy through the pack that the car driven electrically did. Remember, just because the car is generating electricity and using that to drive the motor doesn't mean the pack is cycling - the pack only sees the net difference between the power used and the power generated. Under most driving condition with the ICE on, the engine is producing more or less the amount of power needed to move the car, with only a small balance to/from the pack.
Correct, with most other electric vehicles, I'd worry about losing battery bars, but with a volt, they'ev babied the battery with a great temp management system and they don't allow you to charge the battery all the way up to capacity and all they way down to zero. The battery does act as a temporary buffer between the high reveling ice and your changing driving conditions, but it's barely barely wearing the battery in charge sustaining mode.
 

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What saghoqst said is exactly correct, and thanks for clarifying the ICE connects to the wheels as low as 35 mph, instead of 70 that many people say.

I also want to emphasize to the original poster that the traction battery is ALWAYS online when driving, even when the ICE is running. With the nature of how the volt operates, the ICE is never generating the exact amount of energy that the vehicle demands. Thus there is always some energy going into or leaving the battery, even in extended range mode. This is the beauty of how the Volt operates, or any PHEV vehicle. It doesn't make since that all cars and trucks don't work this way. In time, they will....or be fully BEV.

-Eric
 

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It sounds like the OP is considering buying a used Volt that was never plugged in, or already bought it. This was VERY common around 2014-2015 when TONS of volts were entering the used market from G.E. workers. They were never plugged in, ALL OF THEM! or maybe one out of 1000 were ever charged.

Anyhow, for a Volt that was never plugged in, the battery would still have seen charge-discharge cycles, but less vigorous cycling than a Volt that was plugged in daily. However for a Volt is charged every day, because the battery is so pampered by the TMS and BMS, many (including me) expect for the Volt's battery to be good for 15 years or over 200,000 miles. Many early Volt owners have over 100,000 miles on their 6+ year old Volts with absolutely zero (noticeable) battery degradation. Weather the BMS is "hiding" battery deg or not by adjusting the charging window is a hotly debating subject. I'm a little flip-flop with my own beliefs. I used to be a strong anti-window adjusting believer, mostly from an early interview with Andrew Farrow. However I'm starting to believe that my 2011 Volt with 110,000 miles is indeed adjusting it's charging window based on recent driving behavior. But that's beside the point and I am rambling.

Just buy the Volt, or drive it! it's a wonderful automobile.

-Eric in Georgia (used to be Texas) 2011 Volt #1819
 

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It sounds like the OP is considering buying a used Volt that was never plugged in, or already bought it. This was VERY common around 2014-2015 when TONS of volts were entering the used market from G.E. workers. They were never plugged in, ALL OF THEM! or maybe one out of 1000 were ever charged.

Anyhow, for a Volt that was never plugged in, the battery would still have seen charge-discharge cycles, but less vigorous cycling than a Volt that was plugged in daily. However for a Volt is charged every day, because the battery is so pampered by the TMS and BMS, many (including me) expect for the Volt's battery to be good for 15 years or over 200,000 miles. Many early Volt owners have over 100,000 miles on their 6+ year old Volts with absolutely zero (noticeable) battery degradation. Weather the BMS is "hiding" battery deg or not by adjusting the charging window is a hotly debating subject. I'm a little flip-flop with my own beliefs. I used to be a strong anti-window adjusting believer, mostly from an early interview with Andrew Farrow. However I'm starting to believe that my 2011 Volt with 110,000 miles is indeed adjusting it's charging window based on recent driving behavior. But that's beside the point and I am rambling.
Your comments lead me to observe that these large fleets of Volts that were being driven on gas were, in essence, maintaining their battery SOC around the GM-engineered minimum level for long periods of time... don’t know if leaving a battery at a low state of charge for long periods of time has any effects on longevity...

Wonder if any of those drivers experienced Reduced Propulsion Mode when driving up long, steep hills without engaging Mountain Mode to create a battery buffer... or if not plugging into the grid overnight ever led to problems with starting the car on a cold winter morning because proper battery temperature management could not be maintained on the limited amount of available battery charge, or even problems in the late afternoon after the car had been sitting in the hot sun all day long in peak summer temperatures with limited power in the battery...
 

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Your understanding is incorrect. Unless you're accelerating hard, the car will start the transition to Power Split at 36 mph, and once in Power Split, it will stay there all the way down to 30 mph.

55-60 is about where it switches from single motor EV to 2 motor EV, though, so possibly that lead to the misunderstanding. It's a throughly complex little beast...
This is unclear to me. My understanding is that "power split" refers to propulsion power being supplied by both motors, i.e., two-motor configuration. You seem to be saying that the Gen 1 Volt enters two-motor operation sooner and at lower speeds during Extended Range Mode driving than it does in Electric Mode driving.
 

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This is unclear to me. My understanding is that "power split" refers to propulsion power being supplied by both motors, i.e., two-motor configuration. You seem to be saying that the Gen 1 Volt enters two-motor operation sooner and at lower speeds during Extended Range Mode driving than it does in Electric Mode driving.
In the SAE papers GM engineers wrote about the Volt, they used Power Split to describe the case where the ICE is on and connected to both MG A and the ring gear, and only for that case. The four operating modes of the 4ET50 transmission are described as Single Motor EV, 2 Motor EV, Series, and Power Split.

It is true that the car enters Power Split at lower speeds than it enters 2 Motor EV, but that's not surprising since the efficiency benefits are much larger and the curves driving it are different.
 

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Thanks for the youtube. I am impressed, when I think i have located all the youtube I find new libraries. Good information on motor relationships.
 

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I'll also endorse saghost's clear explanation of how the first generation Volt works.

It's also worth emphasizing that in the second generation Volt there is no longer a clutch that can disconnect the gas engine from the transmission gears that drive the wheels. So, whenever the gas engine is running it is always mechanically contributing to driving the car. Usually, this contribution is indirect and is relative and moderated by the electric motors and battery pack as in a Prius or other power-split hybrid. There is also a less commonly used mode in the second generation Volt that switches it from being a power-split to a parallel hybrid where the gas engine drives the wheels directly with a fixed gear ratio but with optional assistance from an electric motor.
 
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