It's no secret that Nissan hasn't sold as many battery electric cars over the last two years as it had planned.

The company just sold its 50,000th Nissan Leaf last month, but it had hoped to sell up to twice that number between the start of production in late 2010 and the end of last year.

Now the company is continuing its shakeup of executives overseeing the electric-car unit.

Bloomberg reports today that starting April 1, its COO Toshiyuki Shiga will directly oversee the electric-car business and its share of the associated battery joint venture with NEC.

Hideaki Watanabe, a corporate vice president who had run the electric-car group to date, was shunted aside to become a senior vice president at a supplier.

In the U.S., expected to be the largest long-term market for plug-in electric cars, Nissan sold 9,674 Leaf electric hatchbacks in 2011, the car's first year.

Last year, however, in the face of more plug-in models entering the market, including plug-in hybrids that alleviate range anxiety, Nissan sold barely more than that, at 9,819 units.

Nissan had said for almost two years that it would sell 20,000 Leaf electric cars in the U.S. by this March.

It wasn't until last October that Nissan CEO Carlos Ghosn admitted that the company wouldn't reach its ambitious electric-car sales goals.

That month, Nissan appointed Billy Hayes as its global electric-vehicle sales chief, and reorganized some of its U.S. communications functions as well.

Hayes reports directly to Ghosn, as does COO Watanabe.

Last summer, Nissan's U.S. sales chief Al Castignetti attributed the low sales to three factors: a transition from online reservations to standard dealership retailing, a core misunderstanding of electric-car buyers and what they might want, and greater competition in the key California market from a greater range of plug-in vehicles.

Car dealers and local salespeople may be the weakest link in electric-car sales, in fact, for those reasons and more.

The 2013 Nissan Leaf went into production in January at the company's assembly facility in Smyrna, Tennessee, with some equipment upgrades, a new base trim level, and lower prices.

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