Tom and Ray Magliozzi: Tuneups

Plug-in hybrid alters balance of locomotion

Gasoline engine will supplement electric power from denser batteries.

Dear Tom and Ray: Guys, what's the big deal about plug-in hybrid cars? I've read that various automakers plan to come out with plug-in hybrids in the next two to five years. Isn't a plug-in hybrid just a current hybrid with a battery charger? Is there some additional technology here that I'm missing?

Bob

RAY: Well, I guess you couldput it that way, Bob.

TOM: But if I were to simplify it, I'd say that today's gasoline-electric hybrids use electricity to supplement a gasoline engine, whereas tomorrow's plug-in hybrids will use a gasoline engine to supplement electric power.

RAY: Cars like the Toyota Prius have enough battery power on board to power the cars up to 15 or 20 miles per hour and, after that, to assist the gasoline engine when necessary. That improves gas mileage significantly. You get twice as many miles per gallon as the average car, which is great.

TOM: But the Prius' batteries regularly need to be recharged by the engine, so the gasoline engine still has to run pretty frequently.

RAY: Plug-in hybrids alter the balance. Instead of constantly needing to be recharged by the engine, they get most of their recharging by being plugged in at night.

TOM: So, it's not just the recharge-ability; it's that plug-in hybrids will store a lot more energy on board. That's also why they're not available yet. We're waiting for a new generation of batteries to be ready.

RAY: Current hybrids use nickel metal hydride batteries. That was an improvement over the first hybrids, which used a boatload of Eveready D-cells.

TOM: Within the next few years, carmakers are anticipating the mass production of lithium ion batteries (Li), which are far denser. RAY: Perhaps the greatest advantage of plug-in hybrids, however, is that they'll allow us to address our oil use and pollution by focusing on a relatively small number of power plants, rather than on 100 million individual cars.

TOM: Right. So, once cars run primarily off of the electrical grid, we could add wind power, solar power, nuclear power, cow flatulence or anything we want to our power grid, while retiring dirtier, less-efficient plants. If we follow through with that, plug-in hybrids would be a great step toward energy independence and reducing pollution.

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