Tesla Motors Inc., maker of electric cars, has a battery problem: not enough of them. That’s one reason the shares fell 14.5 percent, the most in nearly two years. CEO Elon Musk blames a shortage of lithium-ion battery cells for trouble filling orders for Tesla’s Model S. Some cars were sent to Europe to satisfy customers there. There will be no relief till next year, he said, when a battery deal with Panasonic kicks in. Tesla also posted a $38 million quarterly loss; revenue rose 6 percent to $431 million.