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Chevy Volt - How's it work?

Chevy Volt - How's it work?

Chevy Volt - How's it work?

(OP)
Chevy says it can go about 40 miles on batteries alone but can go another 200 or so miles using a small IC engine that recharges the batteries.  So, in effect, the "small" IC engine is moving the car.  I'm assuming that performance (acceleration and top speed) are drastically reduced when running on the engine.  Or am I missing something?

RE: Chevy Volt - How's it work?

Why would the performance be compromised?

This is just a series hybrid with a big battery.  It seems that GM are trying to convince the journalists and prospective customers otherwise.  They don't use the word hybrid and refer to the engine as a "range extender".

From what I've read, they're trying to claim that the fuel economy should be measured in such a way that it ignores the fuel used to charge the battery when it's plugged in overnight.  EPA tests usually require the battery to be in the same state of charge at each end of the test (i.e. sensible).

Letting the battery discharge during the conomy test is exactly the same as starting your economy test at the top of a hill.

This car could be another "breakthrough in marketing".

- Steve

RE: Chevy Volt - How's it work?

should perhaps have two separate figures on the sticker - the gallons used per hundred miles, and the externally-supplied kWh to return to the same charge state at the end.  Would take years for people to get their heads around the total cost to go 100mi.  Pure marketing brilliance.
 

RE: Chevy Volt - How's it work?

It's a bit different in that the battery is large enough that most daily trips will never tap the fuel.  Putting an IC engine into is the comprimise they had to make to give the car the kind of range that American's expect.  Many people currently are modifying their Prius's to perform similarly.

And by the way... prior to 2008 (and maybe even now?) the EPA did not require that a hybrid's battery be in the same state as at the beginning of the test.  

A plug in hybrid is a bit of a different animal than a car that gets all of it's energy from gas.  It's an issue because it is illegal for the automakers to advertise any mpg except the EPA's test.

-b

 

RE: Chevy Volt - How's it work?

"Breakthrough in marketing"...I like it.

RE: Chevy Volt - How's it work?

(OP)
- so the car continues to draw energy from the batteries even when the battery voltage is low enough to kick on the IC engine?  The Tesla supposedly will go nearly 250 miles without the IC engine and it will recharge overnite.  It doesn't seem like the IC engine does much - gets you an extra 50 miles or so over the Tesla?

RE: Chevy Volt - How's it work?

Bob,

I am not very familiar with the Tesla, but will it seat 4 passengers, obtain 4-5 star crash ratings, etc.?  My guess is that it is more of a performance car, thus it weighs considerably less, and will have a retail cost significantly higher than that of the Chevy Volt.
 

RE: Chevy Volt - How's it work?

The car continues drawing energy from the batteries even when the "state of charge" is low enough to start the IC engine ... YES ... but remember, the system is (apparently) designed to keep it above (approximately) 30% charged, so there will not be a loss of performance.

The "range" on a long trip that uses up the designed 70% charge, is no different from a gasoline vehicle and you treat it the same way. When the gas gauge goes to empty, you fill it up and keep going, obviously on gasoline power (driving the generator which maintains the state of charge at about 30%).

The Volt is *designed* to be plugged in every night to recharge it. It is an electric car with a range-extending gasoline engine so that it can do long trips. If you don't plug it in, you lose the benefit of running on stored electric power, but at least the car will DO it.

RE: Chevy Volt - How's it work?

(OP)
I think I get it - the car runs on batteries until the battery charge gets to about 70%.  At that point you run on gas + battery.  When the battery is down to about 30% you are "out of fuel" and you need to recharge the batteries.

RE: Chevy Volt - How's it work?

No, not quite ...

The car runs on batteries alone, without gasoline engine operation at all, until the state of charge reaches about 30%. At that point, the car continues running on batteries but the engine starts and recharges them at the same time, so the car keeps going (on "net" gasoline power) and the state of charge is kept at about 30% by running the engine to roughly match power demand. It will go as long as the tank of fuel will last in this mode just like a regular car, and you can fill up the tank and keep right on going, just like a regular car. When the opportunity arises to plug the car in ... the batteries charge to 100% and this process can be repeated. From the point of view of "running out of fuel" there is not ever a "need" to plug in the battery ... but if you don't, you will not get the fuel saving benefit of the plug-in hybrid system.

RE: Chevy Volt - How's it work?

"fuel saving"?

It's only really tax saving.  Fuel is burned elsewhere, with much less tax than anything you can buy at a pump.

And we all know that when tax-saving schemes become popular, they disappear.

- Steve

RE: Chevy Volt - How's it work?

It's gasoline (petrol) saving.  I have seen the results of studies(propoganda?)that indicate that 40 miles would cover 80% of US driving needs.   

RE: Chevy Volt - How's it work?

You guys just don't seem to get it.  Maybe it really is a breakthrough in marketing.

They may not be burning gasoline at the power station, but it's more than likely some form of hydrocarbon fuel that's being used to "fill" the battery.
 

- Steve

RE: Chevy Volt - How's it work?

We understand you Somptingguy, but the taxes are much different on this side of the pond.  Our fuel taxes in the US are much lower on gas/petrol (10-20%) vs. what you pay in the UK (closer to 120%).  We also generate a larger share (but still small) of our energy from hydroelectric plants.  It's also much harder to shovel coal into your car while driving than to rely on the battery.

-b

RE: Chevy Volt - How's it work?

(OP)
Brian:

When you get down to that 30% level then all the car's power needs are coming from the gas, right?  That's where I don't understand how you can get by with what is called a "small" IC engine.  Performance of the car must be limited at that point, right?  Or is it that the electric drive is more efficient at getting power to the wheels?

RE: Chevy Volt - How's it work?

The small engine runs even when you're not demanding power.  By running continuously it can keep the battery charged enough that it can deal with short high demand periods (accelerating from a stop). Obviously if you're towing a boat up a mountain at 80mph you'll probably overwhelm the little IC motor.

RE: Chevy Volt - How's it work?

Regarding the fuel being burned elsewhere, it's true, but an electric powertrain is more efficient at light power demand and at regenerative braking, AND the central power plant has a higher thermal efficiency than a mobile gasoline engine ever could be, so the net amount of energy input is less. And that's assuming that all the electrical power is generated using fossil fuel. In the USA, that might be substantially true (for now), but there are more options for generating electricity renewably (wind, solar, hydroelectric, etc) or at least via non-fossil-fuel-consuming methods (nuclear).

Here in Canada, a very large fraction of the electricity is hydroelectric or nuclear. Wind power is still a small fraction but gaining fast.

The taxation point is a good one, and if plug-in vehicles become popular, I wonder how long it would take the authorities to do something about this.

RE: Chevy Volt - How's it work?

Well, yes and no. By the time you've distributed the electricity, put it through the charger, and then through the car's own electronics, you are looking at something like 80% distribution (power station output to input to battery) efficiency at best. In terms of CO2 emissions there is surpisingly little difference between an EV such as the Tesla, and an efficient diesel with 4, rather than 2, seats. The Volt actually uses about 50% more power than the Tesla in EV mode.



 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Chevy Volt - How's it work?

Having just suffered through 2 weeks without power and having a generator in my driveway due to Hurricane Ike, I have wondered how if I were to have had a Volt I would have worked that into my electrical scheme.  Would a 6 Kw generator that already had some dedicated loads, fridge, freezer, a few fans, lights, laptops, etc have had enough spare capacity to also charge a car that I needed for gasoline runs for gasoline that I needed in order to run the generator plus getting to work the past week?  Would the device for charging the car work with a generator?

All in all, it has given me some pause regarding a plug in car.  I had more devices to plug in than I had generator capacity to accommodate.

rmw

RE: Chevy Volt - How's it work?

Well, you'd just drive around in battery depleted mode. That isn't ideal, effciency wise, since you are lugging a dead battery around, but it would work. And to be honest it only takes 16 kWh to charge it, so a 6 kW genny should handle that.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Chevy Volt - How's it work?

rmw : With an inverter & a little ingenuity you could use the Volt as your generator.

bvanhiel : I'm pretty sure the tow rating on the Volt will be zero.

Here in SC 50% of our electricity already comes from nuke plants and they are getting geared up to build more.

RE: Chevy Volt - How's it work?

I read that the engine in that vehicle is rated at 120 kW and the generator generator is rated at 53 kW.  Sounds like some bad matching to me.  Anyway, 53 kW should be enough for the cooker, hot water and A/C.

- Steve

RE: Chevy Volt - How's it work?

53kW should keep you and your neighbors on both sides humming along as though the power never failed.  
 

RE: Chevy Volt - How's it work?

"bvanhiel : I'm pretty sure the tow rating on the Volt will be zero."

I guarantee someone will try.

-b

RE: Chevy Volt - How's it work?

dunno.. priuses seem to come with a trailer hitch.
 

RE: Chevy Volt - How's it work?

The generator in the volt should be less than its peak HP. The generator just needs to provide the average power plus a bit extra to recharge the batteries. the smaller ic engine will weigh less and will not suffer throttling losses.

Luck is a difficult thing to verify and therefore should be tested often. - Me

RE: Chevy Volt - How's it work?

"I read that the engine in that vehicle is rated at 120 kW and the generator generator is rated at 53 kW.  Sounds like some bad matching to me."

Try using 120 kW continuously on any road with the possible exception of the autobahn and the Nürburgring and your license won't last long. If anything, given the attention given to the Volt's aerodynamics 53 kW should get you (un)comfortably over the speed limit on a flat road.
 

RE: Chevy Volt - How's it work?

If your generator is only rated at 53kW, the engine is too big.  Behind all the marketing poop, this is just a series hybrid.  An overly powerful engine is pointless (unless figures look good in adverts).

- Steve

RE: Chevy Volt - How's it work?

...with a big battery.  That's the whole point.  People are spending $10k to convert their Prius's to something similar.  I'd love to have one here in Atlanta right now.

-b

RE: Chevy Volt - How's it work?

It's the electric motor that's rated at 120kW.  The IC engine and generator output is 53kW.

-b

RE: Chevy Volt - How's it work?

I stand corrected.

53kW is fairly piddly for a 1L IC engine though.  At least it is in the civilised world...

- Steve

RE: Chevy Volt - How's it work?

A little higher specific output than the 430 HP 6.2 l Corvette.  And I'm sure it is tuned primarily for optimum BSFC.

RE: Chevy Volt - How's it work?

It's a 1.4 litre engine, non turbo, 4I, now.

As you say it'll be tuned for optimum bsfc, for a very limited number of operating points, and will then use the electric drive as a CVT.

So if they've got their heads screwed on they should manage >30% thermodynamic efficiency across the entire operating range.

 

 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Chevy Volt - How's it work?

Latest news is that the engine will run at just 5 setpoints.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Chevy Volt - How's it work?

Reminds me of spending a few hours on a diesel-electric (a.k.a. Intercity 125) listening to the engine, trying to work out which point it's operating at.  A bit sad really.

- Steve

RE: Chevy Volt - How's it work?

Greg, where does your "latest news" come from?  Or can't you say?

- Steve

RE: Chevy Volt - How's it work?

Why no turbo? Then they could have reduced the size even more. 0.6 liters would not be unrealistic, right?

RE: Chevy Volt - How's it work?

... but would raise the cost of an already expensive vehicle even further.

GM already has a small-engine family of 1.0, 1.2, and 1.4 litres which are all the same basic design, and this is one of them. The Cruze will use the same basic engine, but with a turbo.

"why not the 1.0" - probably market acceptability, probably noise level during highway driving, etc.

A smaller engine isn't necessarily the most efficient. The RIGHT-sized engine is the most efficient.

RE: Chevy Volt - How's it work?

How many setpoints did a 125 have? do you know how they choose them?

Apparently that info is available somewhere on this website  http://media.gm.com/volt/# , I was told about it rather than finding it.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Chevy Volt - How's it work?

I would love to know more about the 125's engine control systems.  Given my age and where I grew up, that train was the epitome of technology.  Paddington <-> Plymouth journeys were and still are a pleasure.

All the WWW mentions of the Paxman Valenta engine state that it develops 2250 BHP at 1500 rev/min.  But if you listen, you can clearly hear different engine speeds and loads in different situations.  From (vague, beery) memory the engines seem to run at two distinct speeds.  I suppose one is best BSFC (flat running), the other, rated power (acceleration & hill climbing).
 

- Steve

RE: Chevy Volt - How's it work?

The Volt's main design purpose for GM is to usher in a new power source away from the ICE.  By having a complete electric drive and battery, the back-up power (right now a gas engine) can be switched to a fuel cell in the future if it becomes a viable solution.  The Volt is simply a "transition" platform.  The same drive technology is used on the Equinox Fuel Cell Research Vehicle.  GM is investing countless dollars on researching the technology.

- Kyle

Kyle Chandler
www.chiefengineering.net

"To the Pessimist, the glass is half-empty.  To the Optimist, the glass is half-full.  To the Engineer, the glass is twice as large as it needs to be!"
 

RE: Chevy Volt - How's it work?

countless?  I'm sure they're counting pretty carefully at this point!
 

RE: Chevy Volt - How's it work?

Hell, they're probably sending some "muscle" around their facilities to shake the lunch money out of their engineers!  Times are difficult.

Kyle Chandler
www.chiefengineering.net

"To the Pessimist, the glass is half-empty.  To the Optimist, the glass is half-full.  To the Engineer, the glass is twice as large as it needs to be!"
 

RE: Chevy Volt - How's it work?

Wait until the hacks are out to see the potential of the Volt. Some of the Prius hacks are amazing. You can enter a drive plan and in doing so the car can figure how much power it needs to generate in route for the trip. It may do it early if the car needs heat or it may wait until the most uphill portion of the trip. It will try to arrive at its charging point with empty batteries. With GPS and transmitted stoplight data the car will pace itselt for minimal stoping or even slowing down.
It can charge itself at night when the day/night rates drop to their cheapest.
The engine generator battery inverter could provide emergency power at home or anywhere if needed. One Volt could jump charge another if ever a problem arose.
You could charge the batteries form a special internal combustion engine/furnace that generates power while it heats your home.
The goal is to waste as little heat as possible.
This site has a few good articles http://autoelectronics.com/
Vin  

RE: Chevy Volt - How's it work?

Who gets different electric rates based on time of day?  We certainly do not.

RE: Chevy Volt - How's it work?

They also do in the UK. If you have any aluminium smelters and/or large coal fired power stations near you then you probably do.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

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