VIDEO: Animation showing the power flow in the Chevy Volt
There has been a fair bit of discussion and controversy in the last couple of weeks on the interwebs about the exact nature of the powerflow and battery charging in the Chevy Volt. Back in July GM's Larry Nitz discussed how the charge sustaining mode would work. As with parallel hybrids the battery is generally kept between about 35 and 85 percent charge. That means when the battery reaches its "depletion" point it still has a significant amount of charge left. The range extender has less power output than the the electric drive motor is capable of (100 hp vs 150 hp) but it has enough output to work in most day-to-day driving conditions. The range extender doesn't normally try to charge the battery fully as that is deemed to be less efficient and more costly than holding the battery at the minimum until the car can be plugged in. For the times when more power is needed such as acceleration or hill climbing some of the reserve battery power is available to be used. The battery can be drawn down below the "depletion" point to about 25-30 percent. When this happens, a combination of regenerative braking and some surplus power from the range extender will bring the battery back up to the minimum. A video after the jump shows the various modes and the power flow.
Gallery: 2011 Chevy Volt
Gallery: 2011 Chevrolet Volt Live Reveal
[Source: General Motors]
Reader Comments (Page 1 of 2)
tankd0g 9:47AM (10/01/2008)
So it works exactly like I said it would. I'll buy one when it's going for employee pricing and $9000 in incentives plus the tax rebate. Then it MIGHT make sense.
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Ignatius 10:32AM (10/01/2008)
Don't hold your breath.
Bing 11:22AM (10/01/2008)
Umm.... what?
How does it not make sense? You lost me...
This is an amazing machine. @$4/Gal average and most likely rising by the time this comes out, I'd say using no fuel at all (with the commute I have) looks pretty attractive.
Turbofrog 11:29AM (10/01/2008)
I just don't understand the hostility towards the Volt.
Even Tesla is banking on a PHEV version of their Model S to reduce costs to more realistic levels in the short term.
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tankd0g 1:12PM (10/01/2008)
The hostility from me is towards Bob Putz. Honestly if they he had just STFU and just came out with this like Toyota and the Prius I wouldn't have anything to say. But he had to make a bunch retarded claims so he deserves the ridicule.
Turbofrog 1:55PM (10/01/2008)
Except that it seems to be able to do absolutely everything he's claimed.
And it certainly does more than any hybrid that's ever come before, or looks to be available in the same timeline in the future.
Franz 11:36AM (10/01/2008)
I thought it would be a range extended EV... but it seems to be just less more than a prius!
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MikeG 2:02PM (10/01/2008)
Sorry Franz, but do you understand what Range Extended EV means? It means it is an Electric Vehicle, that functions only on Electricity (that's the EV part) with some part that that will use a non-electric fuel to generate electric power for it when it must travel past its max range. In a Volt, you never have to put gasoline in it to have full function, if you never go more than 40 miles.
In a Prius, the Electric and Gasoline engines run in parallel. The Electric engine has little range or power and both motors are required for instances when you need power.
John 11:58AM (10/02/2008)
yes in a way it is very much like a Prius, but the battery is much much larger, a prius can go what a couple miles on pure electric and it can only do so under 10mph, this can do that 40 miles running at 60, or there abouts. the principle is the same, regen braking and a small engine to create electricity and power the car once the battery runs dry. its the same idea, taken to the next level with more battery meaning more range and more speed within that range.
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usbseawolf2000 2:43PM (10/01/2008)
Volt can be an EV for the first 40 miles. The remaining 300+ miles will function like a hybrid (the power from gas engine and battery can combine and drive the wheel). It is important to note that, it does not matter what drives the wheel. What matters is where the power comes from.
On cold mornings when the battery is too cold to function, Volt will run on gas engine first before warming up the battery pack.
Volt will function like a part-time electric car or a hybrid other times. It will depends on how and when you use it.
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BillySharps 3:05PM (10/01/2008)
I really doubt that cold will affect these batteries much. New chemistries seem to operate over a much wider temperature range than "regular" laptop batteries. The Wikipedia article on iron phosphate chemistries says, "The batteries can operate from -50 °C to over 75 °C and will not explode or result in thermal runaway even under severe conditions..."
So unless you live somewhere really really cold and drive the volt in -76F weather, I think you'll be ok. Not many people live in Antarctica, though.
JH 10:48AM (10/02/2008)
Like it shows in the video, the Volt's wheels will ONLY be driven ONLY by the electric ONLY motor ONLY, at all times ONLY. The engine just charges the batteries. Is it clear?
usbseawolf2000 12:11PM (10/02/2008)
JH,
"The engine just charges the batteries. Is it clear?"
If you watched the video, it clearly shows the power from the gas engine goes two directions. One to the wheels while the other goes to the battery.
The gas engine makes less than 100hp. If you floor it in the charge sustain mode, addition power has to come from the battery. Therefore, you are powering the Volt with the power from both gas engine and the battery. This makes it a hybrid. Is it clear?
BTW, the official SAE definition of a hybrid define a hybrid by the power sources, not what drives the wheels.
ebow 1:18PM (10/02/2008)
Yes, output from the engine goes directly to vehicle propulsion. In the form of electricity. The wheels are turned by an electrical drive unit. The ICE functions as an electrical generator.
Ignore the vague statement at the beginning of the video. At 1:45, it says "a gasoline / E85-powered engine generator seamlessly provides electricity to power the Volt's electric drive unit while sustaining the charge of the battery in a buffer zone."
So you're both more-or-less wrong, according to what GM has said here. The battery is sustained, not charged, and if you floor it, all the horsepower and torque come from electricity.
This page has a pretty good description:
http://gm-volt.com/2008/09/27/how-charging-of-the-battery-works-in-the-chevy-volt/
usbseawolf2000 8:05PM (10/01/2008)
You are assuming Volt will use A123 cells but not the LG Chem. Define "operate". Will it pump out still 150 hp? Nope. At -20 deg C, the pack will loose half the energy (range cut to ~20 miles) and discharge less than half the power (~70hp).
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Chris M 12:33AM (10/05/2008)
The power would be reduced, but the energy would remain unchanged - the molecules that store the battery energy don't up an disappear when it gets cold, they just slow down.
GM most likely already took that into consideration, after all, they are headquartered in Michigan, where it gets extremely cold every winter. They could have the gasoline engine come on during extreme cold temperatures and use the waste heat from the engine to warm the passenger compartment and the batteries. They could also use electrical power to warm the batteries when plugged in for charging - a well insulated battery pack wouldn't take much power to keep warm.
usbseawolf2000 8:21PM (10/01/2008)
MikeG,
"In a Prius, the Electric and Gasoline engines run in parallel."
Prius is a series-parallel hybrid. A parallel hybrid is the Civic hybrid. Series hybrid is the Volt. Prius is a hybrid of the Civic hybrid and the Volt. The advantage of a parallel hybrid is the low cost without EV or plug-in ability. The advantage of a series hybrid the EV range but at twice the cost.
Prius has advantage of both Civic Hybrid and the Volt. Prius costs about the same as Civic Hybrid and have ability to drive in pure EV mode. The Hybrid Synergy Drive in Prius is so adaptable / flexible that it can have have the "right" battery size that makes sense. A simple planetary gear set can blend the power from both gas and battery.
I believe the next step is PHEV-10 because if you are going further than 5 miles away from home, you will be on the highway anyway. Gas engine does a pretty good job on the highway so leave the EV part for city driving.
Does it make sense to charge the Volt for 5+ hours to drive just 45 mins on the highway?
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Bill 10:07AM (10/02/2008)
"Does it make sense to charge the Volt for 5+ hours to drive just 45 mins on the highway? "
Let me think for a fraction of a second on that one... YES. It does. The energy from those 5 hours of charging costs less than $1. So a gallon of gas ($3.75 lately) vs. $1 in electricity? How can that possibly NOT make sense? It's a break-even value proposition within a fairly short period of time, even assuming the high initial cost of the Volt. Do the math.
usbseawolf2000 10:15PM (10/02/2008)
Bill,
When was the last time you charge an electronic device for 5+ hours so that you can use it for 45 mins? Laptop? Camcorder? Cell phone? I would not find it practical.
Scott K. 1:03PM (10/02/2008)
While I really like this car, it sounds like those who can't plug in their Volt would not get any of the benefits (for example, those who live in an apartment--like me). Once the battery reaches its "depletion point", I'd have no choice but to drive it with the gas engine on as long as I owned it. That's assuming, as the article said, that the engine only maintains the minimum charge as opposed to actually charging it back to 85%.
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