So small battery PHEVs are the way to go - as evinced by Toyota with the PHEV Prius.

The main thing is to make an ICE car as efficient as possible with as little cost (and hence battery size) possible.
This makes for the possibility of electricity maximising strategies for cars; particularly on predictable commutes where you know where the choke points are, and use the electric drive there, rather than on the first 14 miles driven each day.
Or better still, you tell a GPS where you are going (that day) and it calculates a maximising strategy based on traffic data.
So the US should reduce their battery tax credit so that it maxes out at 4 or 5 Kwh and spread the love more widely.

GM, however, might have other ideas.

While batteries seem relatively expensive, every trip has a first few miles and oil use/expense/start-stop engine maintenance can be eliminated by short range EV batteries.

A year from now, the 15 mile range 2012 Prius plugin sales may clearly confirm this.

Considering the long lead time to develop new products (particularly with new technology such as PHEVs), Toyota must have figured out this many, many years ago. No wonder that they managed to put the new Prius PHEV right on the sweet spot in the diagram. Well, in fact, this is not a big surprise, since Toyota has been promoting this option for a couple of years.

"US policy would produce more benefit (per dollar spent) by supporting research on battery cost reduction, enforcing air emission reductions in power generation and transportation, and encouraging adoption of HEVs and SMALL-CAPACITY PHEVs.

And I will gloat, "Hah! Told ya so." The smaller PHEV battery pack that offers a 10-20 mile all-electric driving range incentivizes routine trips becoming shorter whereby more may be conducted without having to drive; a factor probably not fully considered in the study, but still significant. The BEV incentive is to maintain long-distance driving, over the cliff of human stupidity.

I think most people who buy a PHEV would charge the cars when they could. After all, they will have paid a considerable premium (over a HEV or an ICE) to buy the car, so they would want to get the best out of it.
And hence would charge whenever they could.

This would lead to increased demand for at work and mall parking charging as people will want to charge more often if they have a smaller batteries.

This means that more charging would be done during the day (rather than at night) which is probably not what the utilities want.

Nonetheless, say you had a charger which could charge the car in 3 hours (Prius pHev) but had it parked at work for 9 hours, you could devise an optimum charging strategy which would minimise the impact on the grid, charging when demand was lowest (or low).

The smaller batteries of these PHEVs makes for lots of usage optimisation, both in terms of charging and use of the electric power (which is lots of fun for the engineers).

There's a problem with PHEVs that most people don't consider - the problem of NOT using your engine enough.

If saving fuel is your goal you would have a battery pack large enough to cover your normal driving habits and rely on the ICE for those trips that are outside this range, right? Trips like that could actually be few and far between and you might end up going for months without the engine becoming active. So what's the problem with that? Answer - bad gas.

Many fuels have what amounts to a half-life. Gasoline is so highly refined it has one of the shortest half-lifes: The shelf life of gasoline depends on the type of gas and the storage conditions and can range from a couple months to a couple years. One wild card is that gas you buy at the pump may already have been in storage for anywhere from days to months.

What makes gas go stale? Usually the first thing that happens is the lighter chemicals in it evaporate, leaving behind a heavier, less peppy product. Gasoline is an ideal motor vehicle fuel partly because it vaporizes readily to form a combustible mix with air. If it sits unused, however, its more volatile components waft away, leading to poorer engine performance. It's hard to tell how much punch your gas has lost without scientific testing, but don't worry — though your car might start a little harder, it'll still run (assuming it ran before), and there's little risk in burning the fuel if this is all that's gone wrong.

The second cause of bad gas is oxidation — some of the hydrocarbons in the fuel react with oxygen to produce new compounds, almost all of them worse than what you started with. When oxidation becomes a problem, you'll know it without lab tests — the gasoline gives off a sour odor. If you pour some into a glass container, you'll see it's turned dark, and you might find small, solid particles of gum. Using oxidized gasoline is a bad idea, since the gum can clog your fuel filter, create deposits in your fuel system (especially the injectors), and generally hurt performance.

Finally there's the problem of contamination. Water, which can cause gas-line freezing and other problems, is the main culprit — it usually gets into stored gas via condensation as temperatures fluctuate. If the gas is relatively fresh, a "fuel dryer" additive (basically isopropyl alcohol) can help by combining with the water to make a burnable mix that can be run through the system. Another potential problem caused by water is bacteria, although that's not nearly as common. Gas contaminated with dirt or rust is a no go, as the crud will foul your engine.

The push for reformulated gasoline using ethanol (such as E10, aka gasohol) has heightened concerns about gasoline stability. On its Web site Chevron claims "federal and California reformulated gasolines will survive storage as well or better than conventional gasoline," and I can't find any good test data to dispute that. The fact remains that ethanol is hydrophilic, meaning it tends to draw moisture out of the air, so theoretically gasohol should become contaminated more easily than pure gasoline.

The shelf life of gasohol is difficult to determine — proponents claim it's similar to that of pure gasoline but present no hard data. Anecdotally speaking, boat owners and survivalists — people who often deal with stored gasoline — report a much shorter shelf life for gasoline-ethanol blends and advise against storing them long-term.

Diesel has a longer half-life but biodiesel can have a shorter one IF the water/bacteria issue comes up. The most stable fuels are heavy or bunker oil, which is why it's used in ships, and natural gas.

All-in-all I'd recommend that PHEVs be fueled with NG: It's cleaner burning, lasts long in the tank, can be replaced easily with a renewable version (both in the car and in the infrastructure of the country), is already piped to most buildings in North America (making home refueling as possible as home recharging) and (for those who think FEVs are the future) it can be used as a feedstock in the production of hydrogen.

What's not to like?

The fuel can be butanol or propane in a sealed tank for vehicles that operate seldom in range extending mode, but the car computer can insist the the standard fuel is used up before it becomes stale and replaced.

Automobiles with a short all electric range can be built with very cheap lead acid batteries as was the first CALCARS Prius plus. Lighter weight high power lead acid batteries are already being prototyped with the EFFPOWER bipolar batteries.

They VOLT with its expensive elaborate system and large engine was designed to kill all talk about electric cars for GM.

Wright thinks, correctly, that automobiles that are efficient enough can be bought already and only large vehicles with high gasoline or diesel consumption need improvement where the extra costs will pay off.

Infinite amounts of liquid fuels and electrical energy is available indirectly and directly through the use of nuclear energy upon the earth and not relying solely upon the sun to provide nuclear energy to the earth.

The high price and low availability of liquid fuels is artificial and due to speculation and the decisions of the major world governments to allow the speculation to continue. ..HG..

You're right Peter, with small batteries you don't have to worry about bad gas/diesel, but then you do have to worry about using up good gas/diesel. Damned if you do, damned if you don't.

Interesting thing:

Propane is a fuel that does not have evaporative losses (sealed tanks) and no gum formation (no oxidizing because of... sealed tanks). Perhaps using propane dissolved in gasoline to pressurize a sealed fuel system and exclude air would eliminate the fuel-aging issues, as well as making cold starting a lot easier.

With the hybrid & PHEV, any combustable fuel may be utilized, including hydrogen. With a utility grid failure, BEV may supplement household power and recharge via photovoltiac solar panels. However, PHEVs in such emergencies can recharge battery packs and supply electricity immediately.

Prius owners were not too happy with the pre-2010 bladder tanks.

The Volt is using a sealed and pressurized system, GM seems to have solved the aging gasoline issue in the Volt. The only weird thing about this system is that you have to press a button, then wait a few seconds for a pump to equalize the pressure before you can open up the gas cap prior to refueling. I believe the button is next to the fuel cap.

Now, a 100 mile EREV with a tiny LPG fueled wankel engine might be interesting, heck even a single cylinder ICE with a walbro carburetor would be fine. That fuel would never go bad.. would you have to add some lubricant to the LPG?