Via O'Reilly Radar
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Lately there’s been a spate of articles about breakthroughs in
battery technology. Better batteries are important, for any of a number
of reasons: electric cars, smoothing out variations in the power grid,
cell phones, and laptops that don’t need to be recharged daily.
All of these nascent technologies are important, but some of them
leave me cold, and in a way that seems important. It’s relatively easy
to invent new technology, but a lot harder to bring it to market. I’m
starting to understand why. The problem isn’t just commercializing a new
technology — it’s everything that surrounds that new technology.
Take an article like Battery Breakthrough Offers 30 Times More Power, Charges 1,000 Times Faster.
For the purposes of argument, let’s assume that the technology works;
I’m not an expert on the chemistry of batteries, so I have no reason to
believe that it doesn’t. But then let’s take a step back and think about
what a battery does. When you discharge a battery, you’re using a
chemical reaction to create electrical current (which is moving
electrical charge). When you charge a battery, you’re reversing that
reaction: you’re essentially taking the current and putting that back in
the battery.
So, if a battery is going to store 30 times as much power and charge
1,000 times faster, that means that the wires that connect to it need to
carry 30,000 times more current. (Let’s ignore questions like “faster
than what?,” but most batteries I’ve seen take between two and eight
hours to charge.) It’s reasonable to assume that a new battery
technology might be able to store electrical charge more efficiently,
but the charging process is already surprisingly efficient: on the order of 50% to 80%, but possibly much higher for a lithium battery.
So improved charging efficiency isn’t going to help much — if charging a
battery is already 50% efficient, making it 100% efficient only
improves things by a factor of two. How big are the wires for an
automobile battery charger? Can you imagine wires big enough to handle
thousands of times as much current? I don’t think Apple is going to make
any thin, sexy laptops if the charging cable is made from 0000 gauge
wire (roughly 1/2 inch thick, capacity of 195 amps at 60 degrees C). And
I certainly don’t think, as the article claims, that I’ll be able to
jump-start my car with the battery in my cell phone — I don’t have any
idea how I’d connect a wire with the current-handling capacity of a
jumper cable to any cell phone I’d be willing to carry, nor do I want a
phone that turns into an incendiary firebrick when it’s charged, even if
I only need to charge it once a year.
Here’s an older article that’s much more in touch with reality: Battery breakthrough could bring electric cars to all.
The claims are much more limited: these new batteries deliver 2.5
times as much energy with roughly the same weight as current batteries.
But more than that, look at the picture. You don’t get a sense of the
scale, but notice that the tabs extending from the batteries (no doubt
the electrical contacts) are relatively large in relation to the
battery’s body, certainly larger in relation to the battery’s size than
the terminal posts on a typical auto battery. And even more, the
terminals are flat, which maximizes surface area, which maximizes both
heat dissipation (a big issue at high current), and surface area (to
transfer power more efficiently). That’s what I like to see, and that’s
what makes me think that this is a breakthrough that, while less
dramatic, isn’t being over-hyped by irresponsible reporting.
I’m not saying that the problems presented by ultra-high capacity
batteries aren’t solvable. I’m sure that the researchers are well aware
of the issues. Sadly, I’m not so surprised that the reporters who wrote
about the research didn’t understand the issues, resulting in some
rather naive claims about what the technology could accomplish. I can
imagine that there are ways to distribute current within the batteries
that might solve some of the current carrying issues. (For example, high
terminal voltages with an internal voltage divider network that
distributes current to a huge number of cells). As we used to say in
college, “That’s an engineering problem” — but it’s an engineering
problem that’s certainly not trivial.
This argument isn’t intended to dump cold water on battery research,
nor is it really to complain about the press coverage (though it was
relatively uninformed, to put it politely, about the realities of moving
electrical charge around). There’s a bigger point here: innovation is
hard. It’s not just about the conceptual breakthrough that lets you put
30 times as much charge in one battery, or 64 times as many power-hungry
CPUs on one Google Glass frame. It’s about everything else that
surrounds the breakthrough: supplying power, dissipating heat,
connecting wires, and more. The cost of innovation has plummeted in
recent years, and that will allow innovators to focus more on the hard
problems and less on peripheral issues like design and manufacturing.
But the hard problems remain hard.
