Automakers are planning to develop hybrid vehicles that have large battery packs and can be plugged into electrical outlets for recharging, so they can run much farther on electricity alone than conventional hybrids can. But it will be years before factory-made models are available. Now, some institutions are funding their own plug-in R&D and even acquiring plug-in fleets by hiring companies to add larger batteries to existing hybrids and modify their electronics.

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