The auto industry's rollout of new 42-volt electrical systems is going to be stereotypically slow and staggered across model lines.

Forecasts indicate single battery, 42-volt architectures won't be in production in all vehicles until 2020 or so. Most automakers are opting for a costly transition period when cars and trucks will have two batteries, the current 14-volt system and the 42-volt assemblage, because some components presently can't handle the increased juice. A switch straight from 14-volt to 42-volt would overwhelm the industry, some argue. “We wanted to make one jump and keep just one battery,” says John Miller, the lead engineer on Ford Motor Co.'s 42-volt product development program. “But you'd have to expect everybody in the industry to retool at the same time.”

The auto industry is switching to a 42-volt architecture because the 14-volt system has hit critical mass, preventing automakers from introducing such features as drive-by-wire and electronic valve control as well as more entertainment and business capabilities.

The first vehicle to feature a 42-volt system should debut next year in Europe; PSA-Citroen might be first, but Renault SA, Adam Opel AG and Mercedes also are working on programs. North America will follow in 2003.

A Standard and Poor's study says 25%-35% of vehicles in North America, Europe and Japan will have 42-volt systems by 2010. Around 2012, dual voltage systems will peak, appearing in 80% of vehicles. By 2020-2025, all cars and trucks should have a single battery, 42-volt architecture, according to industry estimates.

That's not exactly an expeditious changeover. And it's twice as long as the last time the auto industry increased vehicle architecture voltage; it took only about 10 years during the 1950s and 1960s. Automakers and suppliers point out there's five to eight times more electrical components on a vehicle than 50 years ago.

The introduction of 42-volt systems into cars and trucks arguably is automotive's biggest technological advancement since at least the 1970s when gas shortages pushed the industry to make major fuel economy improvements in less than a decade.

While consumers most likely will be most interested in the improved in-vehicle entertainment options, most automakers initially will use the larger power capacity to combine the starter and alternator into an integrated starter-generator (ISG) unit. Best described as a second engine, it will be mounted on the crankshaft between the engine and transmission, and is expected to provide fuel economy gains of 10%-20% by producing power while idling, accelerating in low-speed range and converting kinetic energy to storable electric energy when braking.