Suppliers Say 42-Volts Starts Next Year

Yes, it's been discussed, and for some time everyone's agreed that future personal vehicles will be laden with electronic components and features that suck power far in excess of today's 12-volt vehicle electrical systems.

But it seems like it's been discussed for a long, long time. Now Siemens AG and Mannesmann VDO AG, to name just two of the suppliers planning a heavy presence in the new age of vehicle electricals, say that they're ready to pull the trigger on 42-volt electrical systems.

Siemens indicates that its first 42-volt starter-alternator-flywheel systems will be supplied for application to vehicles as standard equipment in Europe "in approximately one year."

Meanwhile, Mannesmann - whose Atecs automotive and industrial operations are in the process of being acquired by Siemens and Robert Bosch GmbH - also has big plans for 42-volt power, but on a perhaps less-aggressive timeline. And those plans may be altered in light of the Bosch/Siemens presence in Mannesmann's future.

So the Siemens application may be the beginning of the 42-volt "era" unless, as some believe, a Japanese supplier gets to the starting gate first.

Siemens says its system will have peak output of 8 kW, with an efficiency of "more than 80%," which the company says compares with current 12-volt systems' 1.5 kW and a maximum efficiency of 70% that drops to 30% at high speed.

Siemens also says a noteworthy feature of its system is that it is inherently "wear free and maintenance free due to its contactless (brushless) design."

The company expects the system to be used with automatic start-stop vehicle operation for zero fuel use at standstill in traffic; the system also eventually will facilitate the use of electromechanically actuated valves, electric power steering and electrically driven air conditioning systems (requiring about 3 kW).

Although maximum output is 8 kW, Siemens says its system can deliver 15 kW for short peaks.

Just prior to the announcement of the Bosch/Siemens/Mannesmann linkup, Eckhart Kern, Mannesmann's vice president - sensors and systems, tells WAW that his company will have its "Dynastart" starter/generator on an upcoming German production car, but probably not before the Siemens system is in production. Mr. Kern believes 42-volt systems will see fitment primarily for newly developed powertrains, where it can be designed in from the start.

Like the Siemens system, Mr. Kern says Dynastart will incorporate a stop-start function and, of course, provide instant engine starting at any time.

Providing enough power for the myriad electrical convenience items vehicles now carry is an increasingly important aspect of 42-volt adoption, says Mr. Kern, as some current vehicles are "pushing the limit" of 12-volt electrical capacity. He says it's not unusual these days to have vehicles where the radio may cut out momentarily under sustained braking, for example, because the overall electrical load is too great.

That's why Mannesmann is promoting an interim step, primarily meant for integrating with existing vehicle systems: a DC-to-DC controller and voltage stabilizer that "prioritizes" electrical needs in a hierarchy that ensures important components always get power.

"After all," says Mr. Kern, "you don't want something critical to cut out when you apply the brakes hard."

Mr. Kern says the DC-to-DC converter will be in production sometime next year, helping to bridge the power gap until full-scale 42-volt systems are more prevalent.

"It will be in exclusive cars (to start), but at the end there will be pressure on the industry to adopt 42-volt systems," he asserts.

Forty-two volt's holy grail, he continues, is a possible 20% reduction in engine energy consumption, due mainly to the eventual ability to produce a "beltless" engine in which all ancillaries are electrically driven. Mr. Kern says electro-mechanical valvetrains, electronic power steering (and further out, electric brakes), and an electrically driven water pump are possible right now, but "at the moment, all of these systems are limited by 12-volt capacity." And don't forget the potential to reduce wire gauge throughout the vehicle by two-thirds, and wiring weight by a similar amount.

So when every supplier's eventually offering the "best" 42-volt stuff, what's to choose between them?

"Maximum efficiency," claims Mr. Kern. "Particularly the efficiency of the starter/generator at low speeds." In addition, he believes packaging will be a factor. For example, he says, some current small European vehicles can be fitted with electronic power steering (EPS) and air conditioning - but not both.