Last week luxury electric sports car company Tesla Motors announced a major charging station build out, but a Cornell University researcher has cautioned that further scrutiny may be required.

Two of the greatest barriers EVs need to overcome in order to compete with gasoline vehicles are range and charging time. You can fill your gas tank in 10 minutes and drive 300 miles, so until people get similar performance from EVs, it will likely be difficult to get large-scale consumer acceptance.

The Tesla announcement said customers can get 3 hours of driving time from a 20-minute charge. But 20 minutes provides 40 kilowatt hours of charge capacity, which would only equal a 3-hour – 140-mile – drive if you travel at 47 miles per hour, Paul F. Mutolo, PhD, told Breaking Energy. Keeping an expensive sports car under 50 mph could be challenging for some drivers.

Dr. Mutolo works at Cornell’s Energy Materials Center, one of a set of DOE-supported centers addressing battery challenges for vehicles and grid-based applications. Mutolo said he is in favor of moving to EVs, but the transition must be done in a safe and efficient manner.

Tesla’s website says the Model S uses automotive-grade, lithium-ion battery technology. “The nomenclature is interesting. There are lots of types of lithium ion batteries, but none have been optimized for vehicles,” Mutolo said.

“There is a lot of work going on now in Universities, like Cornell, and in government labs on fully-optimized batteries for vehicles, but that work is really just getting started. It’s only been around for five years and will take some time,” said Mutolo.

The batteries that recently grounded Boeing’s new Dreamliner aircraft for several months due to fire risk were also lithium ion technology. Tesla Chief Executive Elon Musk told aviation analytics and advisory firm Flightglobal in January that the lithium ion batteries used in the Dreamliner are “inherently unsafe”. But the only difference between Tesla’s and airline batteries is the control system that manages power going into and coming out of the battery, explained Mutolo.

“Tesla has a very sophisticated system for this, but they still cannot be charged quickly.” This characteristic of lithium ion technology is why our phones and laptops take so long to charge even though the batteries are so small, he said.

“To my knowledge, Tesla is still using the same batteries that are in our laptops.”

But Mutolo remains optimistic about the future of EVs.”Whether it’s battery- or fuel cell-electric technology,  we are just in favor of helping it be the safest and most efficient possible.”