Tesla Motors, the famous battery-car manufacturer backed by internet nerdwealth tycoon and nascent rocketry kingpin Elon Musk, says that approximately 40 per cent of the cars it has made have a technical fault which could cause them to spontaneously catch fire - but only in a minor way.

In a statement posted on its website but not circulated to the press (as is normal with Tesla announcements), the firm says that it has decided to initiate a safety recall after an electrical fault occurred in one of its $100k Roadster sports cars:

The 12v low voltage auxiliary cable is physically isolated from the main battery pack in the rear of the car... [it] chafed against the edge of a carbon fiber panel in the vehicle causing a short, smoke and possible fire behind the right front headlamp of the vehicle. This issue is limited to the 12V low voltage auxiliary cable and does not involve the main battery pack or main power system.

Apparently the issue only affects the Roadster models 2.0 and 2.5: earlier 1.5 vehicles don't have the offending cable. This means that some 439 cars will need to have their auxiliary power cables checked and fitted with a protective sleeve, a procedure which can be done in the field and requires "approximately one hour".

Thus far the Roadster is the only car that Tesla has delivered. As of June this year it said it had shipped 1,063 of them, with a remaining order book of 110, indicating that the fault affects around 40 per cent of the firm's deliveries.

Early Roadsters also required after-sale modifications, as they were shipped with a transmission that could not deliver the promised neck-snapping acceleration (the Roadster's main claim to supercar status, as in other respects its performance is well below that of a petrol car in the same price bracket*).

Tesla's repeated assertion that the fault has nothing to do with the main battery or power supply circuitry is understandable, as a Roadster is basically a big lithium-ion battery on wheels. In general, as any reader of the gadget press knows, li-ion batteries are prone to spontaneous overheating and fires - quite annoying even in the case of relatively tiny laptop or iPod units, and presumably very scary were such to occur in a Roadster.

Sooner or later as li-ion cars become more widespread - which seems set to happen, as Tesla has secured a $465m federal loan facility for the purpose of building its more-mainstream Model S - there will no doubt be some battery fires. But overall a tank of petrol seems likely to remain significantly more dangerous than a li-ion battery pack which holds a lot less energy. ®

Performance Bootnote

*A Roadster offers excellent supercar style acceleration - going from 0-60 in under four seconds. However it is governed to a maximum speed of 125 mph to avoid damaging the batteries, noticeably slower than an ordinary Vauxhall Astra.

That wouldn't normally be a reasonable beef to raise against the Roadster – such speeds are always illegal and mostly irrelevant – but the Roadster is squarely in the supercar market with its sexy Lotus body, two seats, tiny boot and $100,000 price tag. A petrol car in this price bracket, such as the Porsche 911 Carrera S, can reasonably be expected to show top speeds around 180mph on the test track.

Recharging time and range are a actually the main issue for the Roadster, however.