All Charged Up Over 42- Volt Systems By Rob Wilson The days of the 12-volt automo- tive electrical system are numbered. With the increasing power demands of tomorrow’s vehicles, it looks like 42- volt systems are just around the cor- ner. It’s expected the first such vehicle platform will come together in Europe, but complete conversion on a world- wide basis will follow at a fast and fu- rious pace. This was evident at the re- cent SAE Automotive Congress in Detroit. Electric wiper motors were a great advance nearly 45 years ago, but to- day we’re looking at converting to electrically driven steering systems and braking systems. We need more power to heat up our catalytic converters faster to control cold start emissions. We have new lighting, creature com- forts and entertainment systems being added to automobiles every model year. Detroit was once known as the Mecca of mechanical engineering. Now itis fast becoming the Oz of elec- trical engineering. Did you know we’re putting solid-state gyroscopes in ap- proximately 100,000 automobiles per month? In the Navy we played cards on the gyroscope. The BEI solid-state gyro is half the size ofa paper clip. It is used to generate an input for the break- ing system to stabilize vehicle control in various Cadillac, Mercedes, Volvo, BMW and Volkswagen models. Some auto builders are set to go across the board with this stabilizing device on all new models. Not that this little device forces us to the 42-volt electrical system. It is more the cumulative impact of myriad new electrical subsystems and components that is forcing this revolution. There are technical inno- vations on hold because of the power shortage. New concepts like hybrid drive systems or electrical valve actuation need accommoda- tion. The cost and complexity of today’s automotive electrical sys- tems have gotten out of hand. So there is an absolute gold mine for auto builders in implementing totally integrated electrical systems. It’s hard to say if more money will be saved in wiring and component costs or in the car assembly process. A major payoff is expected on both sides. Many components will be sim- plified and others eliminated. Redun- dancy should be greatly reduced. Assembly should be a breeze. Automakers also see much more efficient automobiles with lower emissions and lower fuel con- sumption. An electrical device only consumes power when it is operat- ing. So all the parasitic losses asso- ciated with belts, pulleys and idler mechanisms can be eliminated with the completely “electrified” car. At least that’s the fine theory of it all. With strategies like multiplexing and pulse width modulation, the ap- propriate voltage levels can be pro- vided for various systems. So if it is desirable to retain a 12-volt power supply for conventional headlights, that can be easily facilitated. Higher voltage means thinner filaments and that means shorter mean time to fail- ure in a world full of vibration and thermal shock. One of the biggest changes in the 42-volt systems will be the starting and charging system. It appears JUNE/JULY, 2000 likely the starter and alternator will be combined on one package and mounted between the engine and trans- mission. The Sachs Automotive DynaStart crankshaft starter genera- tor (CSG) is such a device. This par- ticular one is a 42-pole synchronous machine with permanent magnet field excitation. The one I saw at SAE was intended for engines up to approxi- mately 4L in displacement. The starting cycle is quite differ- ent. A conventional starter spins the engine at low speed and fuel is sup- plied and ignited right away and then the engine sputters up to idle speed. In the advanced starting cycle, the CSG spins the engine all the way up to idle speed before fuel is supplied to the engine and ignited. This results in con- siderably lower cold start emissions. The usual suspects are hard at work on the new 42-volt systems. Johnson Controls, Yazaki, Valeo, Bosch and Delphi to name a few. There’s a whole array of control mod- ules, 36-volt lead acid batteries, lithium polymer batteries and such in a high state of preparedness. Ancillary elec- trically driven systems are ready to go. Once proven in the automotive sphere, the 42-volt electrical platform will spread quickly to other vehicle types and equipment, including heavy- duty. It looks to me like most of the pieces are there. It remains for one bold program to light the fuse. Gentle- men, start your motors. Rob Wilson is president of Diesel & Gas Turbine Publications. Reprinted with permission, Diesel Progress, North American Addition. Page 1 of 1