To cram more charge into the lithium ion battery of the Nissan Leaf electric car, Nissan Motor Co.'s battery engineers turned to the tap for inspiration.
Their breakthrough: Top off the battery with three extra minicharges at five-minute intervals at the very end of charging. It is similar to an expert bartender waiting for the foam to die down before topping off a beer with a couple of tap blasts.
"In our company, we talk about additional charging using this example of how to pour beer," Taiichi Onoyama, expert leader at Nissan's electric and hybrid system engineering department, said at a conference in Tokyo. He illustrated the technical seminar with a PowerPoint slide of a cold brewski.
The maneuver packs an extra 0.7 percent of energy into the battery. Not much, but it can make a big difference in an electric vehicle.
The secret lies in allowing the cell voltage to dip a bit between charges, just like the foam on a beer. The lower voltage allows the battery to accept more charge.
It means a slightly longer charging time. But just as Germans don't mind waiting the textbook seven minutes for a perfectly poured pilsner, most drivers don't mind the extra charging time for a completely topped-off battery.
Said Onoyama: "We have not received any complaints."