[engnrng]

Congratulations to GM for following through with their mule and for exciting so many people in such a worthy endeavor as reducing consumption of fossil fuels. However...
Not sure I understand this concept. When the battery runs low at 41 miles, do you pull over to wait until the ICE recharges the battery? If the ICE has enough hp to charge the battery with enough juice to also drive the car, how is it different from the hybrids that have been around for a decade? Is the overnight charging and 40 mile range really the main attraction? That is certainly great for most people most of the time, but there have been electric cars, like the EV-1, with more than twice that range - RAV4, for another. Or, is the main attraction that after the electric range, the gas ICE kicks in for as long as there is gas? For that insurance, you are carrying a few hundred pounds of gas and engine all the time, even if you don't need it. Some people have taken a hybrid, added more batteries, and acheived a 40+ mile all electric range, with mpg well in excess of 120 - is that similar to the Volt idea? Looking forward to responses helping me to understand the enthusiasm on this site.

Thanks in advance!

 

[Koz]

You should visit the FAQs sections and poke around the appropriate post sections listed on the Home page.

Basically GM has targeted a battery that will last 10 years or 150,000 miles and is capable of 40 miles all electric range (AER) at the end of the battery's "useful" life. The car will be fully highway capable as a Battery only Electric Vehicle (BEV) for this AER. The ICE is only used in a genset to generate electricity to power the traction motor and/or charge the battery. GM has said they are designing the car to have full capability (100mph, ~8.5s 0-60mph, etc) under all operating modes (all electric or range extending). The genset is targeted to be rated ~54KW. The AER is expected to come from roughly 50% of the rated battery capacity. GM is indicated the charging range will be something like 80%-30%. They anticipate the cotrol algorithms to maintain 30%-40% state of charge (SOC) once the range entending mode is reached. This allows the ICE to operate in sweet spots while runnning and also allows the vehicle to arrive with a large percetage of battery charge cylcle capacity.

The major benefits are the AER from plug-in energy and optimized ICE performance when needed. Average on-board cumbustible fuel usage will range from thousands of mpg for <40miles/day users(the ICE will need some maintainance operation) to about 65mpg (200mile/day drivers).

 

[Tom]

Generalization: One of the disadvantages of a series hybrid.

Koz,

You gave an excellent explaination. I just wanted to add a generalization.

A hybrid electric vehicle is one in which propulsion is available from two, or more, energy sources. A BEV, is a battery electric vehicle, and uses one energy series, a battery. The Volt is a series hybrid is one where the propulsion is provided by one source, a motor. A parallel hybrid uses two sources of propulsion. Your question has exposed one of the disadvantages of the series hybrid: the motor, generator, and ICE must all be sized for 1.) long distance, 2.) sustained operation, and 3.) high power dissipation (high speed) driving, less the battery be depleted and you have to "pull over to wait until the ICE recharges the battery."

 

[engnrng]

Thanks for your replies, that helps. So, the Volt is a series hybrid for the range extension mode , but only the electric motor is connected to the drive wheels for propulsion. Simplifies the drive train and "transmission".

If the control algorithm only calls for the ICE when the SOC gets down toward 40%, it will leave plenty of head room for night time electric charging - a primary disadvantage of the Prius. Its control system tries to maintain 80% SOC.

Cool.

 

[J in MN]

As Koz indicated, the Volt ICE is likely to start when SOC reaches 30%, not 40%.

Also, the Prius battery control strategy tries to maintain 60% SOC, not 80%.

J in MN

 

[RRRB]

Two big advantages

The way the Volt is designed gives two big advantages. The one is what has received most attention is charge useage mode --- 40 miles round trip with no gas.
The second advantage, charge maintanance mode (what the Volt does after the battery is discharged to 30% and the ICE comes on) may prove even more important. Here the ICE can be sized for just a little more than average power needs, rather than for peak power. That is, the Volt can have a much smaller ICE system because it can run steadily, very efficient. If a normal car had an ICE that was sized for average power, it would be unable to accelerate fast enough to get on the Interstate safely, and certainly it would be no fun to drive, much less be able to go up steep hills. BUT, with the battery available as a buffer, the Volt can have big power draws from the battery during relatively brief intervals, so the Volt can supply those fast bursts, while its ICE just purrs along.
The fundamental advantages of this kind of design are well demonstrated by that familiar system, the cat (smile, yes, but it is true). Nothing outruns a fast cat (like a cheetah) over a short distance. Very smooth and steady charging system inside a cat. Even the economy model, the ordinary house cat, is pretty quick.