Thanks a lot for this useful summary. I really appreciate it.

Ouch! This is the Catch-22 of BEV. If you do not drive a lot, the potential for any savings is too small to justify the cost. If you drive a lot, hauling the weight of the batteries results in less fuel economy.

a.) "According to the study, 12 kWh usable is required to complete 50% of the real-world drive cycles."

Their chart also shows that < 20 kWh is required to complete > 90% of the real world drive cycles.
Faced with the choice of plugging in at work as well as at night or paying for expensive gasoline, millions of commuters are able to plug in twice a day.

With a 16kWh battery pack, the GM Volt will initially be limited to using only 50% of the capacity, ie 8 kWh.
In the next generation of batteries, it is likely that 10kWh will be usable.

b.) "Most of the fuel consumption increase shown in the road testing was due to the cold battery."
During recharging 5% of the power is converted to heat.
How did they charge the battery and keep it cold?
One seldom mentioned benefit of the plug-in hybrid is that in a cold climate the plug in grid power can be used to heat the battery, the oil in the sump/gearbox and the water in the cooling circuit.
Hence a PHEV could start warm even in mid winter, giving it an efficiency advantage over HEVs and non-hybrids.

Only the picky driver who wants the engine off all the time would care about pure EV mode. The correct measurement should have been gallons of gas displaced. The bean counters should be forced to recognize the importance of the blended EV mode. Stop picking unobtainable targets!

Lulu: If the engine is off all the time, then the amount of fuel displaced is maximized. No?

I, for one, wouldn't be interested in purchasing a PHEV unless it could operate in pure EV mode for at least 90% of my trips.

Kevin:

Not really. As long as you are saving 10 miles worth of gas, it does not matter if you do it in the first 10 miles, or spread the savings out in a 40 mile trip. Limiting high power drain is always a good idea to keep battery life longer.

Their study shows a mean peak power requirement that is higher than the maximum power the IC engine in my 2007 sedan can produce (at around 6000 rpm!). This study appears to apply to a mid-sized SUV (last graph, upper right corner). So don't be too alarmed that the battery pack, which looks to be sized similar to the Volt pack, can't provide enough power to meet all the driving requirements. It wasn't made to.

I'm not sure what they are trying to show with this apparent mismatch of battery pack and vehicle. If they put an average 2 liter IC engine in that test bed it likely wouldn't do any better.

Even a vehicle that can travel 100 miles on batteries will need some type of gasoline range extender. Drivers have come to expect the utmost in flexibility. Most people start feeling uncomfortable when the "low fuel level" light comes on indicating 25-40 more miles of range, and a range extender removes that anxiety.

The peak power is from braking. Most people brake in ½ to 1/3 the distance that they accelerate in that means the regeneration energy is up to 3X the acceleration energy. Regeneration is critical for an EV’s range to be acceptable. I have said for 3 years the drive cycles that exist do not capture what is required to design new drive train systems, torque and speed where the rubber meets the road

its about time someone did some real world testing to point out that just dividing capacity by miles traveled isnt going to give you the right answer. Not everyone wants to plug in every night, not all trips are one stop, not every place is flat, and snow is bad. Looks like the rest of the US should stay away from pure EV's and leave them all in California ( except for Volts, they are going to suck anyway).

This article illustrates the needs for more advanced battery regarding cost, weight, and performance before PHEV will become really practical for the mass of driving public.

For now, PHEV-capable vehicle should be shipped with small packs from 1.5-2 kWh to maximize vehicle production capacity and minimize purchasing cost. The further saving in cost and weight of the on-board charger is also quite nice. These vehicles should be designed to be upgradable to larger battery capacities when battery will be available in larger quantity and lower prices per unit capacity.

For example, if some of the GM Volt is shipped with a HEV version having 2 kWh battery pack, far more units can be produced at thousands of dollars lower cost, prompting much higher sale potential that will result in even further lowering of production cost from higher volume of production. The HEV Volt will have higher payload of several hundred pounds and improved handling from the lighter weight, and the larger sale potential will translate into far more petroleum saving than the PHEV version could ever hope for.

What about the consumers? Most of them will care more about the lower monthly payment on their car loan and lower cost per fillup than whether it is a plug-in or not.

If you drive an electric vehicle or even a low powered gasoline vehicle you cannot expect super high acceleration and fast uphill freeway speeds. In case you drivers out there have not noticed, trucks going up the hill on freeways slow down. Phevs can do the same. A super big engine that is used only part of the time is expensive and inefficient.

Large electric motors are not as inefficient as large gasoline engines at low power, people are tempted to use larger ones than needed on the average. Electric motors and generators can be overloaded for brief periods of time.

Ironless permanent magnet alternator flywheels can have very high peak powers like ultra capacitors but far more energy for the performance. The FLYDRID transmission could be used with an engine that ran at very high speeds and had a large permanently connected flywheel to the engine shaft of a motorcycle engine, but the starting torque could be ultra large.

Hydraulic hybrids may outperform electric hybrids on performance and cost. Batteries will still be needed for plug in operation but high torque electric motors will not be.

With very cheap processing power, micro-controllers can reduce many agressive driving habits and yield more effiency for both gasoline cars an electric cars. ..HG..

Most people drive far too aggressively on the road anyway and spend most of their time drag racing away from green lights and stop signs and then come screeching to a halt at the next stop sign or red light.

With a very clear indicator (the engine turning on and a light indicating that you are braking harder than the battery absorb the energy) you would very quickly entice people to drive more efficiently.

@Lulu

Cold starts are bad. They cost a lot of fuel and the emissions are even higher. So the number of trips completed in EV mode is a very important metric.

@ZachF:

You read my mind. An average peak power of 115 kW? In Europe I guess less than 5% of the passenger vehicles sold has that much power. I think the USABC and DOE meant targeted their battery requirements to Prius/Volt like vehicles, not SUV's.

If you have a vehicle that has a given amount of power, it tends to be used every now and then. But this doesn't mean this power is necessary. Had they used a Ferrari to perform this research, they would have come up with a battery requirement of 300 kW. The outcome was determined by their choice of vehicle.

I wonder how the millions of motorists with sub-100 kW cars get by in traffic?

This study is absolutely ridiculous.

Looking at the chart they've got drivers "requring" over 280 kW (380 bhp) occasionally, and over 110 kW (150 bhp) for much of the time.

There is absolutely no "need" for this kind of power, up to 100 kW is absolutely sufficient for great performance in every type of family vehicle you should be allowed to drive. America, please try to understand this already!

Actualy would be better to study average comute distances. Power need differs due to different weight and aerodynamics. On the photo 4x4 SUV which is quite different animal what we have now from GM.

It is becoming more and more evident that PHEVs battery size should be optimized for maximum liquid fuel consumption reduction on a specific driver basis.

To do that, PHEVs must use modular battery packs composed of (as an example) 4 x 5 KWh plug-in modules for small cars. Of course, each module would be larger for heavier cars.

We could all start with the minimum of one or two modules and add 2 or 3 more as the needs arise and/or the price goes down. This way, a typical PHEV could have an initial price differential of only $4K to $5K (with one battery module).

The ICE vehicles did not start with 300++ hp monsters. The first vehicles barely had 10 hp. Why should PHEVs start with the equivalent of todays over powered ICE?.

I agree with Dave and Clett,

The profiles used resemble the throttle-jockey driving styles of Americans over 1 year ago. Things have changed now (for a significant percentage, anyway). What would a more moderate driving profile do the this study? Most prospective owners of these vehicles will lean more toward hypermiling than than they would aggressive driving.

This study, however, should give GM pause to reflect on their objectives that they are using as discriminators in contrast to the (upcoming) Prius.

"The first vehicles barely had 10 hp. Why should PHEVs start with the equivalent of todays over powered ICE?."

I'd hardly call 40 mile AER over-powered. People have been driving automobiles for more than a century. Cars are not new. Only this powertrain. And driving a maximum of 40 miles before a recharge is below most driver expectations.

I expect that if the modular battery idea will sell more vehicles one of the dozen or so manufacturers announcing EVs will adopt it. While modularity has been built into home computers since the beginning - consumers have not utilized it much. IT tech moves so swiftly that by the time you're ready for a new card, or chip or RAM module - it's smarter to get a new unit because of CPU/RAM speed, software demands, OS improvements, etc.

But guys like Zap will fill the entry level EV demand with low cost, low AER urban runabouts.

Ed Danzer: I'm not sure the peak power is coming from braking, although occasional peaks around 280 kW certainly suggest that may be the case. If it is, then they need to be comparing the mean peak power to the battery peak "regen" power, which is even lower. That being said, I don't think it's a good idea to size your battery pack, motors, and power electronics for the peak regenerative load. You may be able to capture more of your kinetic energy when braking, but the vehicle weight will have gone up so there is:
- More energy required to accelerate
- More kinetic energy to recover during braking (so you have to make the components even bigger)
- More rolling resistance, reducing your steady-state efficiency.
I think you have to size your pack for a reasonable braking event, and people who brake aggressively are going to get shorter range and spend more maintaining their mechanical brakes. This is really a philosophical question though, and there is probably room for both types of vehicles in the marketplace.

gr:

Many (most) ICE vehicles are available with optional motor size and power (4, 6 or 8 cyls) and transmission (manual, auto, 4 to 8 gears) etc.

The battery pack being the highest cost single item on a PHEV, why wouldn't we have the liberty to select its size and power?

Modularity would allow add-on modules latter or initially for drag racers with enough money to spare.

Common sense prefails sooner or latter.

Folks,
I fear that we're on the right track, but we're missing the main point...at least for today's reality. Trying to shoot for an all electric range of 40 miles adds $5000-$10,0000 to the cost of the car. If you're the company producing the car, it's not just the current cost of the battery, but also the huge warranty costs you have to put aside. It's a new drive train and those batteries will have to be replaced sometimes.
For us Greens, we may be willing, and some of us even able, to pay the premium to be able to say "I drive all electric most days".
But the object of the game is to reduce the TOTAL amount of petroleum used, not just put a small number of ultra-efficient cars on the road.

It feels like Roger and Lulu are on the right track that we need to work on something more practical to make a dent and improve it as we go. I applaud GM (that's never happened before!) for their effort on the Volt. But they could afford to produce them and sell them to average people if they had taken a realistic approach. Now they are dependent on tax incentives. I don't know about you folks, but after watching the news the last couple of days I don't know if my tax dollars are going to be able to subsidize much else for a while!!!

“For us Greens, we may be willing, and some of us even able, to pay the premium to be able to say "I drive all electric most days".”

In the context of DaveD's post, I would have top say 'green' means just another clueless consumer who feeds some need to justify their consumption by green washing their consumption.

In my opinion the people who live close enough to work and have the spare cash to afford a PHEV should be taking the bus. It's people like hotel maids and night shift security guards who live way out of the city that are caught in the fossil fuel trap.

In my opinion the people who live close enough to work and have the spare cash to afford a PHEV should be taking the bus.

But public transit isn't all that efficient:

http://www.templetons.com/brad/transit-myth.html

And it isn't all that cheap either, especially compared to a PHEV. Is there any public transit system that will charge you $1 to go 40 miles? If that PHEV cost $50k to buy and operate for 200,000 miles, that's $50k/200k, or about $0.25/mile. Compare it to public transit:

http://www.publicpurpose.com/ut-drvg1960.htm

A factor of 4 less expensive!

The easiest way to push up the cost of a private vehicle is to factor in parking. But I guess that would make the whole thing pretty clear: public transit is only competitive against parked cars, not moving ones.