Plug-in Hybrid Upgrades

Plug-in hybrids have been on a major publicity roll in the US for the past few weeks. From being called a “silver bullet” that could solve the country’s transportation energy woes by Senator Orrin Hatch in January, to receiving a relatively long plug from President Bush during his speech on the Advanced Energy Initiative last week, plug-in hybrids have burst into the general consciousness as an encouraging, positive possibility for reducing our dependence on fossil fuels.

Like standard hybrids, a plug-in uses both a motor and an engine to move the car. Unlike standard hybrids, plug-ins feature much larger batteries, batteries that can store enough energy obtained by charging from the electric grid to power the car in all-electric mode for a much longer range.

The more energy the battery can store, the longer the electric range of the plug-in. The longer the electric range of the plug-in, the less gasoline consumed. It’s by relying more heavily on the battery and the electric motor to move the car that plug-ins tout theoretical fuel economies of 100 miles per gallon or better.

But unlike standard hybrids, flexible-fuel vehicles, or alternative-fuel vehicles, plug-in hybrids are not yet available for purchase from an automaker.

Buyers may be able to convert a standard hybrid to a plug-in fairly soon, however…assuming they have about an additional $10,000 to put into each car.

Hymotion, a Canadian company, recently announced plug-in hybrid electric vehicle (PHEV) upgrade kits for the Toyota Prius and the Ford Escape and Mercury Mariner Hybrids. The company thus becomes the second company to announce a PHEV upgrade strategy, the first being EDrive which is developing a kit targeted at the Prius.

Unlike EDrive, which replaces the original Prius NiMH battery with a larger Li-ion pack, Hymotion leaves the OEM battery in place, supplementing it with an additional lithium-ion battery system.

By leaving the original battery in place, Hymotion can use a smaller lithium-ion battery than does Edrive. For the Prius, the Hymotion kit uses a 5 kilowatt-hour battery that weighs 72.5 kilograms and provides an electric range of 31 miles (50 km). EDrive uses a 9 kilowatt-hour battery that weighs 113.4 kilograms and provides an electric range of 35 miles (56 km).

Hymotion is tentatively pricing its PHEV Prius kit at $9,500 for orders of more than 100. EDrive plans to price its kit in the $10,000 to $12,000 range.

The plug-in kits are a very positive step in the right direction—but they represent only an initial step.

Neither vendor, for example, is changing the original operating strategy of their target hybrids—the guidelines that determine at what speed and battery state of charge the powertrain cuts into and out of electric power, when and how much to boost, and so on. The operating strategy affects the battery power requirements and vehicle performance.

Optimizing the operating strategy is an important part of making plug-ins ready for prime time at an acceptable price. That type of effort should fall to the original manufacturers.

Working through such issues are part of DaimlerChrysler’s partnership with the Electric Power Research Institute (EPRI) to develop a plug-in hybrid commercial van. The partnership plans to deploy six prototype plug-ins this spring to test various battery combinations and operating strategies in different applications.

The availability of PHEV upgrade kits, however, introduces the possibility of a broader development partnership for plug-in hybrid passenger cars that could involve automakers, third-party integrators, customers, and the government. We should seize that opportunity and get started.