There's no Moore's law for batteries

The computing power of microchips may be doubling every 18 months but the capacity of the batteries on which our gadgets depend isn't keeping up. So what's the problem?

There is no Moore’s law for batteries. That is, while the computing power of microchips doubles every 18 months, the capacity of the batteries on which ever more of our gadgets depend exhibits no such exponential growth. In a good year, the capacity of the best batteries in our mobile phones, tablets and notebook computers—and increasingly, in our cars and household gadgets—increases just a few per cent.

It turns out that storing energy safely and reliably is hard in a way that miniaturising circuits is not. A pound of gasoline contains more than 20 times as much energy as a pound of lithium-ion batteries. And then there’s the expense: The battery pack in a Tesla Model S costs approximately $US30,000.

These problems are driving an enormous variety of research projects aimed at achieving a breakthrough in battery technology. Hardly a week goes by that we don’t hear about some magical battery, which always exists only in the lab, that doubles the capacity of current cells.

But here’s a safe bet: Breakthroughs in energy storage technology aren’t coming. Not in the foreseeable future, at least. That’s because it takes years to convert “breakthroughs” in the lab into something that works at scale, under all the conditions of real life use. And the overwhelming majority of innovations don’t survive the process.

This is one reason, Elon Musk said during a recent interview, that he feels safe betting $US5 billion on a “gigafactory” that will produce more lithium-ion batteries, using more or less current techniques and chemistry, than all the world’s factories currently do, and it won’t be completed until 2020.

It’s all about compromise

But let’s not despair. A funny thing happened while engineers were forced to wait for a breakthrough that never arrived. They compromised. They made their designs more efficient. And the result is a new dawn of devices lighter, more efficient, and more capable than anything that has come before.

Take, for example, the Mahindra Genze, a new electric scooter currently marketed to students and young city dwellers. According to lead designer Terry Duncan, the Genze is something that “absolutely” wouldn’t have been possible using the best battery technology available even two or three years ago, even though improvements since then have been only incremental.

At the heart of the Genze is a thorny design problem: How to create a vehicle with decent range and top speed—30 miles per hour, 30 miles to a charge—that has a removable battery pack, so that its owner can charge it indoors, from any wall outlet?

The solution is something the size of a briefcase that weighs 25 pounds. Any heavier and a large portion of the Genze’s potential audience wouldn’t be comfortable hefting it—a fact I verified on a recent test ride. Getting the battery pack to that size wasn’t just about using the best battery, though the Genze’s batteries cost a non-trivial $US1,000, or a third of its retail price. It was also about creatively engineering the entire scooter, which to save weight lacks a conventional frame, instead relying on its external chassis for structural integrity.

Engineers at Dyson are coping with the slow advance in battery tech in a similar way. Dyson’s original cordless vacuum cleaner, released in 2006, ran for only six to seven minutes on a charge, says Rob Green, senior design engineer at Dyson. This meant it was useful only for a quick clean up. The latest version can run for 20 minutes, which means it can clean the whole of a small apartment, completely replacing a conventional vacuum.

That is partly due to batteries, but it’s also a consequence of Dyson’s custom-designed electric motors, which are 80 per cent efficient, compared with an average of about 30 per cent efficiency for typical vacuum cleaner motors.

Perhaps the best example of creativity in the face of limited energy storage is the rise of personal drones. These are possible only because of faster microprocessors and tiny versions of the brushless motors also used by Dyson. Even so, at present Parrot’s AR 2.0 quadcopter drone, one of the best on the market, can stay aloft for only 18 minutes per charge of its battery.

The ‘Drone Delivery’ hype

Drones are a special case of the limitations of current energy storage technology because, even more than in cars and other gadgets, there is a direct penalty for adding more batteries—the drone becomes heavier.

That’s one reason we should all be sceptical of companies promising drone delivery services. For drones to become viable for dropping off packages, as prototyped by Amazon and Google, their flight time will have to improve substantially. Yet there are no breakthroughs in commercial-scale battery tech on the horizon. One alternative is to power those drones with gasoline, but it’s hard to imagine people will put up with skies darkened by the auditory equivalent of flying weed whackers.

Which means we’re not going to eliminate the UPS man until battery power crosses a threshold that might be far in the future. It might not even happen until a time when we’re not even using batteries any longer, but rather some kind of solid-state energy storage device or an advanced hydrogen fuel cell.

In the meantime, all advances in mobile, portable gadgets—including technologies that forever seem just a few years away, like robots—are going to be about compromise. That doesn’t mean that incremental advances in battery tech won’t continue to uniquely enable gadgets going cordless.

One suggested by Dyson’s Mr. Green is the electric hair dryer, which still electrocute a handful of people a year. “It would be a hell of a lot safer to not have any plug circuits in bathrooms at all,” he says.

—Follow Christopher Mims on Twitter @Mims or write to him atchristopher.mims@wsj.com.