A source close to industry planning for changeover to 42V tells WEVTU that virtually every electrical component on present and future vehicles that are now 12V will likely be switched to the new, higher voltage now being widely discussed in the industry: a 36V battery with 42V charging.

The topic will see a raft of discussion at next month's Society of Automotive Engineers Congress and Exposition in Detroit.

Until recently, it had been assumed that lights would stay at 12V due to the ruggedness of bulb filaments at the lower voltage, but with the development of PWM (pulse width modulation) which employs mosfets, durable light bulbs can be used. PWM steps 42V down to the needed bulb voltages for filament ruggedness.

WEVTU has obtained the following list of vehicle systems now on the list for potential use of 42V. Virtually every automotive system is included:

  • Load leveling-active suspension

  • Cooling fan

  • Air-conditioning system, compressor and fan

  • Ignition system

  • Fuse box

  • Starter/alternator or crankshaft generator

  • Headlights (with wiper), fog lights, turn signals, etc.

  • Oil pump

  • Water pump

  • Active engine dampening

  • Electrically heated catalyst

  • Electrically operated: power steering, engine valves, brake assist, heated seats, window defogging, seats, windows, mirrors and sunroofs

  • DC/DC converter

It is evident that at the outset of 42V use, there will be both a 36V and a 12V battery or a 36V battery with a DC-to-DC converter for 12V requirements. Just how long it may be before all components become 42V, if one includes PWM light circuits, is not clear — but one source tells WEVTU the industry will see the first vehicles with some degree of 42V use in about three years and total conversion will start about two years later.

It is pointed out that timing for any one vehicle model will depend on new-platform sequencing by the maker.