Automakers often do comparison ads showing how their features or specs are better than their competitors', but they don't generally trash other makers' designs in public.

Like so many conventions, this one doesn't seem to apply to Elon Musk, CEO of venture-funded startup Tesla Motors [NSDQ:TSLA]. He savaged the "primitive" design of the battery pack in the 2011 Nissan Leaf, the all-electric hatchback that will go on sale in December.

2011 Nissan Leaf

2011 Nissan Leaf

The comments came at during a conference call with investors discussing Tesla's second-quarter loss. following its June initial public offering.

They expanded, more bluntly, on concerns expressed by former Tesla marketing honcho Darryl Siry and others over the Leaf's air-cooled battery pack.

Unlike the water-cooled packs of the Tesla Roadster and the 2011 Chevrolet Volt, which use radiators to dissipate heat, the Leaf must use ambient air and fans to cool its lithium-ion battery. Temperature extremes--whether -25 or 120 degrees F--can make air cooling is a challenge.

Tesla Roadster final assembly, Menlo Park, California, April 2009

Tesla Roadster final assembly, Menlo Park, California, April 2009

Musk said the production Leaf used a "much more primitive level of technology" than anything Tesla had considered putting into production, and predicted that the Leaf's pack would experience "huge degradation" in cold weather and essentially "shut off" in hot temperatures.

Nissan has warrantied its battery pack for 8 years/100,000 miles (as has Chevrolet for the 2011 Volt), which should reassure consumers anxious over the prospect of a five-figure replacement battery pack several years into their ownership.

Every carmaker simulates harsh duty cycles on its battery pack designs before they're approved for production. General Motors has done several tours of its battery laboratory during Volt development, and Nissan surely has a similar lab.

Buyers will have to wait a few years to find out if Musk's words prove prophetic, or if he's just sowing what computer industry analysts used to attribute to IBM and Microsoft: fear, uncertainty, and doubt (aka FUD).

[Earth2Tech via Autoblog]