Breaking news! Chevy volt technically driven by gas engine!

[rgathright]

Originally Posted by brucey

I don't see this as a big deal. If you're going 70 mph the electric motor simply isn't as efficient and turning on the gas motor makes since. Since if you're going 70 you're probably leaving town anyway. Who exceeds 70 mph on short trips?

The 35-40 MPG EPA is amazing though. All that work and they can't best themselves with a base model car costing 1/4 the price. Are those the official figures? I can't find anything definitive yet.

Actually, the savings with electric motors comes in when you are cruising because they can just "sip" on the batteries to keep the car at speed.

Electric motors consume massive amounts of power when taking off because stall rotor current creates a "short" of sorts against the batteries. For this reason, gasoline engines are preferred for getting the car up to speed.

I am planning on using an EV (Nissan Leaf?) in 2011 to drive to work between Lake Charles and Sulphur on the interstate. We have a tall bridge here between towns that prevents the use of your traditional NEV (neighborhood electric vehicle).

[UFO]

Originally Posted by rgathright

The reason why the Volt was supposed to be so impressive (and warrant its price tag) was that it was a series hybrid, unlike any other vehicle to date.

In the original design it was:

Motor -->AC Motor<--> Inverter <--> Battery
..............|
..............|
..............V
.......Transmission
..............|
..............|
..............V
...........Wheels

With these changes, that were not revealed until now, it is:
Motor --> Transmission <--> AC Motor <--> Inverter <--> Battery
.................. |
...................|
...................V
.............. Wheels

I'm not sure why you think this is not a good thing. In this configuration (parallel), either motor can drive the wheels directly, for minimum mechanical losses. If all the ICE could do is charge the battery, you will have an inherent inefficiency converting mechanical energy from the engine to electricity, then back to mechanical energy to drive the wheels. You will have built-in fuel waste.

[Daox]

Originally Posted by rgathright

Electric motors consume massive amounts of power when taking off because stall rotor current creates a "short" of sorts against the batteries. For this reason, gasoline engines are preferred for getting the car up to speed.

Can you give some reference to backup this comment? I'd have to disagree unless I hear otherwise. In my Prius, when pulling away from a stop it uses electric for the first few seconds (depending on if you mash the pedal or not). I wouldn't imagine they'd do this if it were less efficient.

[rgathright]

Originally Posted by Daox

Can you give some reference to backup this comment? I'd have to disagree unless I hear otherwise. In my Prius, when pulling away from a stop it uses electric for the first few seconds (depending on if you mash the pedal or not). I wouldn't imagine they'd do this if it were less efficient.

The internet and electric motor technical manuals are filled this sort of information.

Since the topic is taking off in an EV, with these charts, you are looking for the current consumed at mid-peak torque levels.

Power consumption for a DC motor in columnar format:


AC Motor power curve chart

[brucey]

Yeah, the power curve chart shows very little power being made as the RPM's get higher. On mine, and on a tesla roadster.



My understanding was the same as Daox. They have very good low speed torque but kind of putter out once spinning. My experiences with both of my electric bikes and my modified 1350 watt electric scooter back this up.

Back on topic, I thought that using the gas motor was more efficient at higher speed than the electric motor. Hence the use of "some gas" at that time.

[UFO]

Originally Posted by rgathright

Actually, the savings with electric motors comes in when you are cruising because they can just "sip" on the batteries to keep the car at speed.

Electric motors consume massive amounts of power when taking off because stall rotor current creates a "short" of sorts against the batteries. For this reason, gasoline engines are preferred for getting the car up to speed.

Take a look at the posted graphs. The AC motor in the Prius, like most electric motor applications, actually do not "consume massive amounts of power", they actually peak torque at zero RPM. Peak power occurs with RPM. You may be mistaking power for current, and any AC controller worth its silicon is going to control that zero RPM current.

The very reason that locomotives use electric motors (aka series "hybrid") is that peak torque at zero rpm enables the train to move from a stop. Just try to make a mechanical drive that can deliver that kind of torque...

[cfg83]

Hello -

I can understand this quote :

I liken it to the fixation people have on electric-only driving in conventional hybrids (and their future plug-in versions). Driving for some number of miles on electric power alone might seem satisfying to drivers of, say, a Prius, but if that doesn't make it as efficient as it could be, what's the point?

IMO no one has made the "ideal" series hybrid, aka a completely disconnected ICE (or other electricity generator) :

Hybrid vehicle - Wikipedia, the free encyclopedia

Series-hybrid vehicles are driven by the electric motor with no mechanical connection to the engine. Instead there is an engine tuned for running a generator when the battery pack energy supply isn't sufficient for demands.

However, if the ideal doesn't work in the real world, then that's ok with me.

We heard about this rumor in another Volt thread a few months ago, but GM flatly denied it. I think the denial was a "being secret" thing, just like the article speculates.

CarloSW2

[tjts1]

The ideal series hybrid is the electric car getting its power from a natural gas fueled power plant. No series hybrid or mobile internal combustion engine will ever match the efficiency of even the worst coal fueled electric power plant.

[cfg83]

tjts1 -

Originally Posted by tjts1

The ideal series hybrid is the electric car getting its power from a natural gas fueled power plant. No series hybrid or mobile internal combustion engine will ever match the efficiency of even the worst coal fueled electric power plant.

I'm talking about a different ideal. I don't care about the fuel source. I am only talking about the drivetrain, where the ICE is 100% separate from the wheels. In that situation you should be able to swap out the ICE for any source of energy generation, aka hydrogen fuel cell, or carbon-neutral wood-fueled steam powa, or just more batteries (as you have just stated).

CarloSW2

[dcb]

Originally Posted by UFO

...The very reason that locomotives use electric motors (aka series "hybrid")...

Please lets not call trains hybrids, even in quotes, they only have one power source, it will only further confuse people.