Is it fair to say GM will eat a lot of money on battery warranty work?

I found in that link BSFC charts for Prius Atkinson, not for the Volt Otto.
So it is a bit vague to support anyone claiming 231g/kwh...lower than Prius!
[ame]http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption[/ame]
(see typical values)

As for the conversion losses estimates, let me hold you the idea that Volt and Prius train can share some resemblance, but most of the Prius ICE torque is driven to wheels, not to buffer. That is stated in George's estimate.

A "geek" model, isn't it?

 

I've gotten 48 mpg doing it, but testing it makes me nervous because of the cycle life issue.

Basically the procedure is to let the AER go down to zero, then switch on MM, gas will power the car and charge the battery up to a higher SOC (equivalent of about 14 miles AER), then switch back to normal and drive on electric those 14 miles, then rinse and repeat. It makes me nervous because instead of floating the SOC in a narrow band as designed in CS you're cycling it up and down across a wider band, that can't be good for battery life.

Its also really important to time it just right so you arrive with no AER left when you get home to plug in again (otherwise you burned more gas than you needed to for unused AER).

SO its possible, but not advised.

When MM is raising the SoC I imagine the rpms are higher than if you're in MM at the higher SoC. Its noticeably noisy with significant vibration, but not any worse than some ICE's.

 

I think the cost of battery packs in ten years is anybody's guess. A bigger question is whether GM will be supporting the Volt in ten years. Nissan and Tesla have shown serious commitment to EVs and are likely to continue to support their vehicles. GM not so much.

FWIW, Tesla offers Roadster buyers the opportunity, for a set time period after purchase, to buy a battery-replacement contract. This is not a warranty. It's basically a futures contract: Pay $12,000 now and you get a new battery pack installed in 7 years, with some pro-rated options for exercising the contract earlier or later than 7 years. The Roadster pack is 56 kWh and is liquid-cooled. Presumably they do not expect to lose money on this deal. So, figure that Tesla thinks they can build a 56 kWh pack for less than $12,000 in seven years. Extrapolating, I'd guess a new Volt battery pack in ten years should be around $3,000 but not more than $4,000 plus an inflation adjustment. (Unless GM decides to over-charge because they don't want to service the car or because there are too few on the road to make it worth their while. Though in the case of the Tesla, there will only be 2,500 Roadsters built, so that, too, is a low-volume product.)

 

Plus, these packs are organized into modules. Replacing just a bad module is what will most likely be done.

 

Sorry did not notice george did not post the GM BSFC.. You can find attached. (Originally posted at The BSFC chart thread (post 'em if you got 'em) - Page 20 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com)

The volt uses an Ecotec TwinPort 1398ccm four cylinder(bore 73,4mm, stroke 82,6mm, compression ratio 10,5). It comes from GM family 0, generation 3 engines. The power output is 63kW/4800rpm, 130Nm/4250rpm. BSFC is 230 at 115NM and 3000 RPM. You'll see the generator efficiency is over 92% at that point. If one could get it up to 3800rpm the BSFC drop a bit to 255, but the generator efficiency is up over 93% (and 125NM, the total generator output is higher).

The maps show BSFC + generator efficiency and lines of GM strategy for battery charging including MM mode (higher RPMs) When The engine is used as a range extender for the EV.

 

Curious why you feel the MM recharge is that much worse for the batteries than regen breaking or even grid charging at 240v. I would agree that the MM is a faster charge (will add 14miles in 20-25min as opposed to 75-90 min, so maybe 3-4x), but it is charging the battery well within the sweet spot of SOC, and as long as the car can mange the heat pretty well I don't see it being a cycle killer.

It is a tad harder on the ICE running it harder, but so far RPM have been reasonable (MM recharge RPM have been 2200 to 3000, MM compared to CS mode RPMs usually < 2400). I don't think 3000rpm should be that much harder, its well away from redline. (I did not have a gauge on it when I took it up real mountains in MM, and one of those times it sound lough enough that my wife worried. )

 

Why stop at 2011 Toyota Camry hybrid / 2011 Volt hybrids ??
We're on the 2012 model now.
Doesn't Volt still fail to meet SULEV status?
Doesn't Camry HSD now boast 41/43/39 epa?

Fuel Economy Leaders: 2012 Model Year | Fuel Economy | US EPA

With hybrid Camry's 2012 lower msrp ($21,955) ... you could buy a lot of gas ... except you wouldn't need to because your hybrid Camry epa mileage would be higher than the Volt (... and yes, I'm just sayin' that to mock the folks that used to say that about the Prius 'premium'). I know that there are folks that can work their drive to fit the Volt's electric range - and that this group will out-do the Camry and the Prius epa, So, if the battery issue is managable, and if you got the extra $20K above the cost of a hybrid Camry to throw out there ... then why not.

 

Thanks for the BSFC and generator efficiency graphs. It just go on and show that there is little to gain from running 3,000 rpm vs. 2,000 rpm. There is no way Volt can get 50 MPG.

Prius optimal g/kWh is 220. It gets 50 MPG because majority of the power goes through the mechanical path (superior PSD setup). The car doesn't have a crippling battery pack and showboat complexity.

 

Thank you for sharing. To the other posters, I beg your pardon for the ott-topic...
I only have to say that the "sweetspot" means about 36kw at the shaft.
Cuising cannot absorb that many power, except for high-speed above limit, so some of it shall be sent to buffer. Conversion on charge/discharge does bring efficiency down, which makes Otto engine an underdesigned powerplant for this application with rare use of mechanical path, as USB said.
IMHO, there isn't an easy way to reach 50MPG in this setup.

 

when discussing the replacement of battery packs, that cost cannot be the only factor here. its like saying $30 is a reasonable price for dinner. sure it is!! but i be damned if i will pay $30 if everyone else is paying $20.

we need to examine the alternative costs here. now the Volt is different in that it has a double whammy (another reason why the really really screwed themselves by deciding to be upscale) with potential battery replacement costs and normal ICE maintenance requirements. so there is NO savings here.

average costs for motor pools in maintaining compact ICE is 15 cents per mile. http://www.government-fleet.com/news/story/2011/07/Seattle-Takes-Delivery-of-First-5-of-35-Leafs.aspx estimated (since database is limited) to maintain EVs is 2 cents a mile.

that means an ICE compact, ya the VERY SAME car we push idiots to when they complain a Prius or EV is too expensive, will cost more money in the long run. so buy an Econo box for $15,000 verses a Leaf at $27,000 after incentives. after 100,000 miles you have added $2,000 to the Leaf but $15,000 to the Econo box so now you have a Leaf that is $1,000 cheaper and that DOES INCLUDE the cost of fuel but does not take into account the rising price between two very disparate fuel sources, electricity and gas. which do you think will go up faster in the future?

 

Perhaps at the moment, but it will meet requirements for HOV passes in 2012.

That's actually how I pictured a serial battery hybrid should work. When the SOC hits the low limit, the genset fires up. It only runs at a single output. Any electric generated over what is demanded for propulsion goes into the battery. Hit the high SOC limit and it shuts down.

 

Part of what made the synergy drive so good is its use of the electric motor to supplement power and keep the car closer to its sweet spot. If the Volt had to run the ICE the whole time, or the majority of the time, I would agree it could not even get that close to 50. The point is using it for more of a long pulse-glide approach with the battery providing a buffer to allow the "glide" to be EV driving and to use the generator to keep it in its sweet spot.

Your arguments are not as much why the Volt cannot get 50, but more why it cannot be as efficient as a Prius. In your statements you are ignoring that when the Prius is at 225, its producing 90Nm, which is often more than it needs for actual travel.f With a good pulse-glide technique in the prius, many people get over 60mpg some claiming 70s even at hwy speeds. So I would totally agree the prius still has an efficiency advantage in that its sweet spot is more efficient. My goal is to get the same out of my Volt, but since the engine RPM is not directly coupled to my throttle there is little I can do to pulse-glide. The volt controller is trying to be 'smarter', and keep it at the lowest RPM (quietest ride) that meets is averaged energy demand. It cannot predict future demand so it keeps it at an average (just like the prius does). To get better requires a users with knowledge of the terrain and future demands to push the car into its sweet spot, knowing they can use the excess energy (and not waste it by say parking the car). To get better than the default in the Volt, MountainMode allows us to push it into a more agressive pluse "glide", where the glide is really CD driving. Can we be as efficient as pulse-gluide in a prius? No. Can we be more efficient and maybe approach 50mpg? Maybe.

If you were to try to operate at the 90Nm that a Prius outputs at max efficiency, the Volt's engine would be at about 1800rpm, 245 g/kwh and ~90% generator efficiency. This RPM is about what I see at 65mph in CS mode, getting about 42 MPG with my driving style@60-70F. But if I can get the engine to move up to its 230 g/kwh at 3000 rpm, the Volt reaches an efficiency of 230g/kwh and is producing 115Nm, almost 30% more torque than the 90Nm (Prius's peak efficiency). At this point the ICE can be providing almost all the needed power for driving into the ring gear, which is the most efficient conversion of ICE into motion, with some electricity generated and s channeled into the electricity for the traction motor (which in the power split can be providing a much share of power). Any excess electricity can go into the battery. Given that the system can maintain steady state at the 90nm of power is more than enough for the wheels and traction motor. (At 55mph, the car shuts down the ICE for long periods so its demand is < 80Nm and it is doing its own pulse-glide). But if I want to run at 3000rpm where both the ICE and generator are more efficient, we would have too much power and the only thing we can really do is store it in the battery for a while, then turn off the ICE and "glide" on just the traction motor. Maybe its not 50mpg, maybe its only the 46-47 that George's computations show (and which i've achieved multiple times). But this does provide some supporting evidence that we can improve efficiency using MM.

 

90 Nm @ 1,300 rpm outputs 17 hp. That's perfect for 65 mph.

The reason Volt has mountain mode is because the battery power fades after the SOC (65%?) threshold. Performance will suffer as it ages.

 

Fixed that for you

Otherwise very nice post. It is great to see Volt owners who understand some mechanics and are not just :cheer2: :cheer2: :cheer2:. You bring the number up to six.

P&G in a Prius has (optimally) no traction battery use, while the Volt is being forced to operate out of its native mode of *always* incurring traction battery and MG1 (1 or 2 -- I always forget?) losses from ICE to wheels. This age old comparo of Prius Vs Volt still seems to come down to fact that a serial hybrid drivetrain design is a smart payment for an otto ICE, but not for the Toyota Atkinson ICE used in an HSD. Toyota just went over the top a bit in letting HSD be serial OR parallel, to a large degree without user intervention.

 

The reason Volt has mountain mode is because the battery needs a larger energy buffer in order to supplement engine output during a long steep uphill climb over the largest mountain passes. You could instead try to squeeze more energy out below the 15% SOC but it would not be enough in addition to the battery stress of drawing it at high power from a very low SOC.

As for performance being reduced due to battery power output declining, this is will happen eventually. Fortunately, the Volt has strong performance to start with so the eventual decline after 10-15 years should still result in perfectly adequate perceived performance. Drivers rarely require more than 60 kW during normal driving. High demands, such as driving up long steep mountain passes, will likely happen for typical owners when they have run the battery down to the point where the engine starts running in hybrid mode which will then cover any power output gap.

 

You are leaving out three things: Battery longevity is unknown; the EV is range-limited; and half the total cost of the econobox is spread out over the life of the car, whereas the Leaf requires nearly the full investment up front, meaning a larger loan and more total interest paid, or more money taken out of productive investment or diverted from other possible purchases (i.e. opportunity costs).

You know that I am 100% in favor of EVs. I've put my money where my mouth is. But I also know that my Zap Xebra cost far more to operate per mile than my Prius (or an econobox) due to battery cost and total miles driven being limited by its range. If the Leaf's batteries provide all the range the owner needs for the life of the car, then your analysis is correct. But if it needs a new battery pack at the five year mark because the range is no longer sufficient, or if the owner still needs an ICE car because some of her driving is over 100 miles, then your analysis is incomplete.

What I say is that a two-car household, in most cases, could have a Leaf and a Prius (as I believe you do) or a Leaf and an econobox.

Oh, a fourth thing you left out: How battery aging and rapid advancements in an emerging technology, as well as a growing number of choices in the market, will affect the resale value of the Leaf. The resale value of the econobox is pretty predictable. The resale value of a totally new kind of car is not.

Oc course, a big rise in gas prices would change everything.

 

daniel; your longevity statement works if the batteries dont hold up. the rest is conjecture. gas maybe $3.50 a gallon in 2020 and all this discussion will be for naught.

we may discover the largest oil field in history next month. all that makes my prediction fail.

so lets table this discussion and revisit it in 5 years.

other point. the break even point for EVs is about 100,000 miles over an economy car. so everything beyond that is money in the bank for another EV or a replacement battery pack to run another 100,000 miles.

 

Thanks for the tense correction. Yes I meant "makes" as the synergy drive still has real advantages. And If the PiP had a larger battery I might have gone for it. My daily commute is 32-35 miles and I see no reason to burn gas on that. The Volt is a better match for my usage patterns. Lifetime I'm at over 40 miles per fuel dollar (and 190+ MPG of real gas).

In your answer you describe the Volt as a serial hybrid, but when its running in hybrid mode only uses the "1-motor" serial-hybrid mode in some settings (very low speeds, or when it needs more power for acceleration). When it is most efficient it in its 2-motor extended range mode (mode 4) which is a mixed parallel-serial mode where the ICE drives the ring gear, the traction motor the sun gear. In this mode you can't have both electric motors driving the car at high speed like it does when in 2-motor EV mode because second motor-generator must be used as a generator driven by the engine. This is where the engine begins to directly drive the ring gear. The engine is already clutched to the second motor-generator, so a straight-through mechanical connection is established when the ring's motor-generator clutch is engaged. Compared to Mode pur serial mode, the engine works harder here because it is simultaneously driving the ring gear and the shaft of the generator. In that mode its serial (generator providing power to the traction motor) but also parallel (traction + Ice driving the planetary system). In that mode the traction motor can turn very very slowly (the speed differential between traction and ICE provide the effective output of the planetary system) and the "serial" part of that can be very low power demand. So the Volt has 4 modes it can be EV (one motor), EV 2 motor, serial hybrid (1 motor with generator driven by ICE), or serial-parallel. GM also wanted to make it easy and pleasant for drivers and so made pretty good choices. But knowing what I want I hope to do better.

 

That's twenty years' driving for me. I've never had a car for that long.

 

Here is a link describing the different transmission configurations at a GM website used from training service technicians:

Voltec Electric Drive Unit and High Voltage Battery - GM Techlink