there is no better battery « Manifest Density

Ryan and I have been going back and forth in his comments about the likelihood of carsharing services going electric. I think it’s unlikely because they’d have to spend too much time charging; he thinks they’re a good candidate for early rollout of the charging infrastructure necessary for such a switch. Most recently he said:

In practice, this could be achieved incrementally. Tweak business models over a ten year period through which you slowly switch from gas engines to plug-in hybrids to all electric, over which period, presumably, battery technology slowly improves. Needn’t be done all at once.

I think this is a point that’s worth making here and at some length: “presum[ing that] battery technology improves” is setting yourself up for failure.

In truth, there have only been a few noteworthy improvements in battery tech during Ryan and my lifetimes: longer-lived NiCd and NiMH batteries; some improvement in alkaline batteries; and the popularization of lithium batteries. But look closer and you’ll realize that most of these aren’t actually battery innovations, per se: they’re benefits of the microprocessor revolution. Cheap, smart charging circuitry allowed us to avoid memory effects; to balance load across cells; and to monitor lithium cells’ temperature and voltage as they charge so that they don’t catch fire (well… usually), thereby finally making lithium a viable option for consumer electronics. Those are all important developments, but at this point we’ve wrung about as much as we can out of charging our batteries more cleverly.

None of this has done much to improve the fundamental energy storage densities of the underlying chemistries. These have been known for a long time now, and nothing is going to change them — nor are there any more promising elements like lithium waiting to be tamed (well, none that aren’t radioactive, anyway). The glacial pace of improvement in battery technology really can’t be overemphasized. The lead-acid battery was developed in 1859, for pete’s sake. It’s really heavy relative to the energy it stores, can produce explosive fumes if overcharged, and sometimes requires the addition of distilled water. Yet it’s still the best battery technology we have for supplying the high current necessary to turn over an engine. A century and a half and we haven’t come up with anything better!

It may seem like batteries have improved dramatically — consider the lifespan of an iPod Nano versus a portable cassette player. But this is misleading. In fact it’s a byproduct of more energy-efficient technologies. Which isn’t to dismiss energy effiency! But electric motors are already extremely efficient. And when it comes to vehicles, we’re unfortunately dealing with hard physical limits related to how much energy it takes to move a car. So long as we’re committed to EVs being able to perform like and drive safely near gasoline-powered cars, we will find ourselves with less room for improvement than people would like to think.

I don’t mean to be a downer, but it’s difficult to overstate what a serious problem this is, or for how long it’s been one. Hydrocarbons are an unbelievably efficient way to store energy when compared to electrochemical cells, and I seriously doubt anything will change that. Hopefully I’ll be proven wrong. But smart people have been working on the battery problem for decades and decades, propelled by the lure of the financial bonanza that a breakthrough would represent. And while they’ve made impressive improvements, none come anywhere close to competing with gasoline’s energy density. We’re still an order of magnitude away.

Now of course there are always fuel cells. And nanotech’s vast surface areas may deliver unexpected breakthroughs. But a bet that counts on a better battery is still a very, very bad wager.

This entry was posted on Wednesday, August 20th, 2008 at 2:55 pm and is filed under science. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.