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Is that a brick in your car?

24 February 2012

Regular readers will know that I have been a critic of the Tesla Roadster, especially in light of the seemingly amazing claims being made for it by a particular Robert Llewellyn (Hi Robert!).

In fact, Robert posted a video to YouTube in which he pilloried the Top Gear programme for making the Roadster look much worse than it really is. He came to the defense of the vehicle and started getting all evangelical about the Tesla and the future of EVs in general.

After seeing this, Tesla even let him have a drive in one (ooohh!) and one of the other EV makers gave him one as a bit of a promotional exercise I guess.

I posted a video response in which I sought to take issue with some of Robert's claims and statements.

Right now, regular readers may also be a little confused -- because I often suggest that NZ ought to create its own EV industry -- so what's going on?

Well the Tesla Roadster is a whole different kettle of fish to the small commuter EVs I'm talking about -- it's expensive and not so much a practical EV as a rich-man's toy.

In my video I suggest that the weak-point of the Tesla's design is its very expensive and potentially short-lived battery pack.

Back in 2008 when I made that video, a new battery pack was worth 13,000 quid but now it seems the price has gone up to US$40,000.

And what's worse -- it seems that you can completely root your expensive Tesla Roadster's battery by simply failing to charge it frequently enough.

According to this article on CNet, there have been a number of instances where the expensive lump of lithium that powers the Roadster has been turned into a pretty worthless brick.

That is unbelievably bad!

The reality is that lithium cells prefer to be stored with about 3.8V per cell and if you leave your Roadster in either a fully-charged or almost discharged state, the odds of your battery being damaged increase significantly.

The problem (right now) with lithium-ion cells is that when they're fully charged or discharged, a number of irreversible chemical reactions take place. Left long enough in either of those states, the cells will lose capacity and may even represent a fire risk.

These are some of the subtle issues that surround the design of EVs using existing technology -- and possibly explains why so many of them (and hybrids) are actually avoiding lithium technology in favour of the older, but less effective, nickel-metal hydride technology.

A much better option for EVs (from a battery longevity, safety and robustness) perspective is the lithium iron phosphate (LiFePO4) technology. Unfortunately it is more expensive and doesn't offer the same energy densities that lithium ion does at present.

Does all this matter?

Yes it does -- if you're planning on building an EV that is a direct analog of a fossil-fueled vehicle. That's where Tesla (and others) have got it wrong.

Today's "practical" EV, bearing in mind the limitations of the technology, is a lightweight car probably built from composite materials, with a comparatively small battery and a range of around 100Kms or so -- no more.

These would be cheap to make, cheap to maintain and capable of replacing a huge percentage of our existing commuter fleet almost immediately. The low energy demands of such vehicles would place minimal extra load on our electricity infrastructure and their smaller size would also extend the useful life of existing roading. Indeed, during peak commuting time, lanes could be set aside solely for EVs - just like they are now for busses. That would make them safer and encourage the uptake of this technology.

Of course it's far too much to imagine that even for one moment, local or central government might see the benefits that could be had from the promotion of such vehicles as a commuter transport alternative to the family car. So, instead, we'll just pour billions of dollars into widening our motorways, importing petrol and dealing with the pollution all this hydrocarbon combustion causes.

What a shame.

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