Stephen Clarke thinks that lead-acid batteries have gotten a bum rap, and he wants to revive their fortunes via the $3 billion and growing Chinese electric scooter market.
Clarke is CEO of Applied Intellectual Capital, an Alameda, Calif.-based electrochemical technology development company that's funded itself through consulting work and a number of spinouts since its 1994 founding.
Among its more recent projects, AIC is working on bipolar lead-acid batteries, a technology that he believes can easily outperform advanced lithium-ion batteries on power density – the amount of power it can deliver in a set period of time – as well as on price.
"Everything you think you know about lead-acid is wrong," Clarke said Thursday at the Opportunities in Grid-Connected Mobility conference in San Francisco.
That's because the lead-acid batteries most people are familiar with – car batteries – are built as cheaply as possible, with a lifespan just long enough to outlast their warranty, he said.
They're also monopolar batteries, the design that still makes up the vast majority of most types of batteries now available today, he said. Monopolar batteries consist of a number of plates stacked in serially coupled negative and positive electrodes and connected by current collectors. This results in a high resistance current path and unnecessary weight, he said.
But AIC's lead-acid batteries are bipolar, meaning that the cells within are stacked in a sandwich construction that utilizes the materials within more thoroughly, he said. That cuts internal resistance a hundred-fold and halves the weight required for the same performance, he said.
Other companies, such as Firefly Energy and Atraverda (where Clarke once worked), are seeking to improve lead-acid batteries. Johnson Controls and Volvo spinout Effpower has been working on bipolar lead-acid batteries.
The problem for bipolar batteries so far has been stability, Clarke said. That is, they tend to have shorter cycle lives than monopolar batteries. AIC has overcome that problem, Clarke said, though he wouldn't reveal just how.
Proof may come in the coming months, when AIC intends to launch a joint venture with an unnamed Chinese company to start manufacturing its bipolar lead-acid batteries for what Clarke called "the world's biggest electric vehicle fleet that no one has heard of" – the 60 million or so electric scooters and bicycles populating China's roadways.
With a typical top speed of 40 miles per hour and ranges of 30 to 40 miles, these aren't the fanciest of vehicles. But with an average price of $800 and a charging cost of about 25 cents per day, they're economical - and China's government has made a big push to see them replace the two-stroke gasoline engines that have played a role in polluting the country's air, he said.
Clarke estimated the battery market for those scooters at $3 billion a year and growing about 15 percent annually. He also said he can supply those batteries at about $70 apiece, compared to the $650 or so he said a comparable performance lithium-ion battery would cost.
Given all the other components that make up a complete battery, he said the weight difference between heavy lead and light lithium wouldn't make that much of a difference.
An emerging battery market for which weight is far less important is for storing energy on the electricity grid, he said, and AIC is hoping to target that market as well.
Lead-acid batteries have been used by utilities for more than a century, but their lower energy density and short cycle life have kept them from wide-scale use, according to a September report by the Electric Power Research Institute.
Clarke disputed that, saying AIC's bipolar design does away with the energy density drawbacks of lead acid batteries. As for cycle life, he cited a lead-acid grid storage battery from Exide Technologies that lasted three years beyond its eight-year projected lifespan – with five years still left in it.