That doesn't make sense. How can all the current from the gas engine go through the battery and still drive the car? While the battery is charging, it can not discharge.

I'm puzzled by this as well. If all of the current is going through the batteries, then discharging from the batteries, there would be additional losses. How it would accomplish this simultaneously I do not know, but I'm not a EE either.

The proper question to ask is, "how much peak horsepower can the car produce once the ICE kicks in?" If it is less than 150 and anywhere near 72 then we have our answer.

Seems that GM doesn't know what they are going to build.

From what I read, all the ICE does is kick on to keep the battery at 30% capacity.

The ICE will run at a constant RPM, providing a constant current when on.

Since the electric motor won't likely be drawing that full current except when accelerating hard, the rest goes to the battery until it's at 30%.

ok, then the follow-up question to Shawn's is: how much contnuous energy can be drawn down from 30% battery SOC before the car says "ICE only" until I recharge ?

So, it must use the ICE/generator to directly power the leccy motors and keep the battery with spec ? Not exactly fuel efficient then.. ideal for a deisel though!

From comments farther down in the thread it appears that the ICE will kick on and off as needed to keep the 'depleted' battery at about 30-35% of charge. When the upper limit is reached the ICE turns off and the e-motor draws down the battery again. At about 30% the ICE kicks in again and repeats. It appears that the charging would be short bursts.

GM's hope is that the 150 hp e-motor will not draw that much from the battery for say 60 mph cruising on the highway. IOW perfect conditions where the power needed is well less than 75 hp.

However perfect conditions are not always present. In 75 mph traffic, or against a headwind, or in stop and go traffic the 'draw' on the battery is going to be relatively strong - meaning that the ICE will be kicking on and off much more frequently. The statements all say that the ICE will be operating at it's most efficient state with the battery used for load leveling. I'm assuming that this means the Atkinson cycle.

That's something that needs to be monitored. How smooth is the 1.4L ICE? How quiet is it when charging? How often is it On - off - On - off - On - etc.

All the direct motive power to the wheels will be from the e-motor.

it seems to me that there is a lot of hoping going on at GM... They might suggest to Volt buyers to drive at 25 mph for optimal performance

Hi All,

This is the definition of a series hybrid car.

The battery still has about the same HP as when fully charged. Something around 150 hp, if what I remember is correct.

The Battery will charge beyond 30 percent - on long down hills, of course.

Then on the next long uphill it will drop below 30 percent, and the engine will come on.

They will have hysterisous in this. That is, the engine probably wont shut off until the car reaches something like 40 percent. Then the car runs along down to 30 percent. This way, the engine restarts wont be so numerous to use up the hybrid efficiency.

Hi All,

Lets get some reasonable understanding of powers here.

Level cruising without wind on the highway at 60 mph, in this size of cars requires about 15 hp. Not 75.

Level cruising without wind on the highway at 75 mph in this size of car requires about 25 hp. Power required to overcome air drag doubles with only this 25 percent increase in speed. But all the power at 60 mph was not aero-related, there is some rolling resistance, thus the power required is not doubled.

Thus, cruising into a 15 mph head wind requires about 25 hp too. Suprisingly, cruising into a 15 mph 45 degree side wind requires more than 25 hp. Because the CdA of the car goes way up. Both the A and Cd are effected. And this effect is more than the reduction in tangent wind speed.

The volt concept is an ideal way to use a diesel in a Hybrid. If the Volt is successful in the market, I will be supprised if they do not come out with a diesel option.

It will be 150hp until it hits its hard lower limit (to protect the battery). Then it will be limited to the power of the ICE minus the conversion efficiency. This is only likely to be an issue on long hill climbs, otherwise I suspect it will cycle over a limited range as you describe.

Rob

Simply put, the battery will just get the difference between the current in from generator and the current going out to the motor. If they are equal, no current will flow into the battery itself.

Rob

donee,

That's a nice rosey scenario, but it doesn't fit well with the 30 mpg GM has indicated in "range extended mode." Seems too many Volt backers are trying to have their cake and eat it too. It is more likely that the Volt is going to need to limit the recharge (if that is what they do) to a narrow band.

They have not stated so far that the engine will run intermittently as best I can tell. Lutz has said all the power from the generator will go through the battery. This seems unlikely and wasteful.

It wouldn't make much sense to charge a large battery more than a few percent. Going from 30-40 would be 20% of the total charge range of the pack (30-80) and would seem a very wasteful thing to do with a plug in. This would give pretty severe mileage hits as soon as one exceeded battery range. For example, driving long enough to finish the 40% charge would cost however long the distance to charge was on gasoline, plus the gasoline used, both at 30 mpg. So if the charging occurred over 8 miles (20% of the claimed electric range), then it would be like driving 16 miles at 30 mpg.

As much as I dislike the chosen configuration for Volt, I'm not going to sit around and allow incorrect information about it to be spread either.

PLEASE PROVIDE YOUR SOURCE.

30 MPG is most definitely not what's been posted on the big Volt website. They had been flaunting the 50 MPG estimate from the beginning up to the annoucement of switching to the bigger 4-cylinder engine... which won't drop efficiency that much.

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Untrue! I posted the following in response to you earlier. Did you not read it or did you not understand it? Want to argue with GM as the source of "incorrect information"? Be my guest. It's not my fault GM is so incompetent at explaining their vehicle in a clear fashion. But don't take it out on me!

At any rate, path through the engine-generator-battery-motor (as Lutz is now claiming) does not appear the most efficient. The vehicle is heavy and has a greater frontal area than the Prius. Do you really believe that is going to get 50 mpg in gasoline mode? :glare:

Here's the link at GM
GM Media Online

How come I don't doubt 30 mpg if they actually use E85.

Knowing GM they probably took a 2.0L off the shelf and short stroked it to 1.4L for added power at low end. That way some yahoo vice president will get a fat bonus for saving the company the money they "should" have poured into the 1.3L turbo diesel. Their sudden switch to a gas ICE seems like this was the likely scenario.

And I can't wait to see how they start the ICE and whether it truly is an Atkinson cycle. I doubt it. Personally I'll bet the ICE will give them the most problems of all. And does it turn the ICE before applying spark to insure proper oil circulation? I doubt that too. I'll bet the new owners will see premature ICE failure.

Now here's what kills me. When this happens, everybody will point to the Prius and tell us our ICE will fail prematurely also. Even though there is no evidence that there is any kind of problem with the Prius ICE.

It'll be the most hyped car at kick off and of course any failures will be hyped as well. And as you all know, crap flows down hill.

Vague references which can easily be assumed incorrectly is a common part of greenwashing.

The statement implies efficiency rating, but is really a calculated cost.

Thankfully, GM hasn't been doing that. In fact, no entity which provides measurements does. Per-Mile is the standard unit used for representing what the consumer pays. The amount of gas consumed is indeed estimated at 50 MPG.

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Really? And where in their most recent press release did they say that (50 MPG)? They didn't. Who is greenwashing now? No, GM gave the figure that works out to 30 MPG. If they were referring to the Volt with the gasoline comparison then that is the mileage they are projecting. It is possible that they were not referring to the Volt and it instead was a poorly worded press statement meant to compare to a generic--I acknowledged that possibility. Whether you like it or not when they provided the basis for cost it became directly convertible to MPG and was no longer a vague cost comparison. GM wants to get away from MPG in referring to the Volt and put it on a utility basis where they can make the strongest claim.

You still haven't explained how the 50 MPG is even feasible with the updates GM has made so far. 50 MPG is an old basis that they don't appear to have reiterated since their unveiling. I'll take "vague references" directly from the source over outdated ones in an FAQ (that are not linked to any direct reference.)

Providing an "equivalent" measure without stating that what it is most definitely qualifies as greenwashing.

The devil is in the details. And in this case, that clearly reveals 30 MPG is not the actual efficiency.

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MPG = Miles Per Gallon

That's miles driven divided by gallons consumed.

Changing the definition without saying that's what was done is misrepresentation... misleading... greenwashing.

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