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Big changes are coming to automobile electrical systems within five years, possibly as soon as model year 2003. That’s the message coming out of Detroit, Tokyo and Stuttgart, as work on 42-volt automotive electrical systems moves out of the laboratory and into the production planning phase.

This also means big changes for the RV industry, as OEMs scramble to make their products compatible with tow vehicles equipped with this new high-voltage system.

The push for a higher electrical system voltage is being driven by the ever-increasing amount of electrical equipment installed in cars, trucks and SUVs. Features such as infotainment systems, personal computers, heated seats and windows, HID lighting systems and on-board 120 VAC power outlets will soon result in power demands higher than are practical with current 14-volt electrical systems.

Moving to a higher voltage increases the efficiency of alternators, reduces wiring weight and copper expense, and makes it easier to introduce new technologies, such as motor-driven power steering, integrated starter-alternators, electrically-heated catalytic converters, electric air conditioning compressors, electrically operated engine coolant pumps, drive-by-wire braking systems and electrically actuated cam-less valve trains.

The change to 42 volts is most appropriate for larger vehicles, including some pickups and SUVs that are popular RV tow vehicles.

Since most automakers are squeamish about taking the 42-volt plunge all at once, most early vehicles will probably contain both a 42-volt system and a downsized 14-volt system. The former will handle high-power chores like starting, lighting and climate control, with the latter being retained to power any “legacy” loads. The 14-volt supply would probably come from a step-down DC power converter or small auxiliary battery.

Of immediate concern to the RV industry is the question of whether a downsized 14-volt system would be capable of handling the extra loads demanded by an attached trailer, which can easily exceed half a kilowatt to operate the absorption refrigerator heating element, recharge a weak set of house batteries and illuminate all exterior lighting. Automakers might balk at building this much reserve capacity into the system, although a higher-capacity version might conceivably be offered on some vehicles as part of an optional “trailering package.”

One solution would have RV manufacturers offer an optional step-down DC converter on any trailer purchased for use with a 42-volt tow vehicle. By tapping directly into the high-power 42-volt source, this strategy would ensure an ample supply of power to the trailer, while simultaneously avoiding any cost increases on RVs that do not require 42-volt capability. It would also eliminate the need for major changes to the RV’s electrical system (provided that the converter also included circuitry for interfacing the RV’s 14-volt exterior lights with the tow vehicle’s 42-volt turn, stop and marker light circuits).

However, the presence of this higher voltage on the trailer hitch connector raises some safety and compatibility issues, probably requiring an entirely new connector design.

Some motorhomes could also become early adopters of high-voltage systems. Diesel engines would be much easier to spin with a 36-volt starter, and the popularity of power accessories on motorhomes makes them logical candidates for the changeover.

Some bus converters are already dealing with dual-voltage systems, since many interstate bus shells are factory-equipped with 28-volt electrical systems. The traditional solution has been to install battery equalizers (made by Vanner, Sure Power and others) to operate any 14-volt appliances and accessories installed by the converter. Presumably, similar 42-volt to 14- volt versions would also become available when higher voltage systems start appearing in the marketplace.

Eventually, as both vehicles and electrical components designed for 14-volt operation become scarce, RV manufacturers and suppliers will probably have to make the jump to 42 volts for virtually all electrical appliances and fixtures. This would involve significant design changes in products including refrigerators, furnaces, DSI water heaters, DC power converters, monitor panels, water pumps, deep-cycle house batteries, AC inverters, and all interior and exterior light fixtures.

Similarly, switches and fuses will have to be rated for safe operation at this higher voltage, and additional precautions might be required to prevent shock hazards.