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1998 Market Update - Electrical

The information provided in this article is excerpted from a presentation made by Doug Barron, Manager of Freedom Battery Design & Application, Delphi Energy & Engine Management Systems. The presentation was made at last year's Independent Battery Manufacturers Association (IBMA) Convention in Chicago, IL.

Barron's comments pertain to the future requirements of automotive batteries. However, they also address the increasing demands placed on the electrical systems of today's high technology vehicles - vehicles which are demanding more and more power to operate an increasing array of vehicle options.

Delphi Energy and Engine Management Systems is a division of the General Motors Automotive Component Group that was renamed to Delphi. Delphi Energy and Engine Management Systems Division was formed by merging AC Spark Plug Rochester Products and Delco Remy. Delphi-E's world headquarters is in Flint, MI, and it has worldwide manufacturing and technical facilities. Its products include batteries, alternators, ignition systems, fuel systems, exhaust systems, spark plugs, and air and oil filters.

Electrical energy demand grows
The age of the integrated circuit and the transfer of some features on automobiles from mechanical to electromechanical have created an almost exponential growth in the demand for electrical energy in today's automobile. Even though there has been continual growth in the electrical power capability of the automotive alternator, the need for the battery to act as a buffer, when electrical energy demand exceeds generation capability, has increased. The result is that the battery must be more capable of handling load cycling requirements; reserve capacities have increased accordingly.

The temperature of the engine compartment began to increase in the 1970s with the introduction of the catalytic converter. Front wheel drive vehicles, low hood lines to improve aerodynamics, additional heat generating sources and increased equipment under the hood have made the thermal environment for the battery extremely harsh.

Figure 1 demonstrates the rise in temperature under the hood to in excess of 90¡ C in many cases. The battery industry has always been painfully aware of the impact of temperature on the life of the battery. Figure 2 illustrates a junk bin study made by an independent third party for Delphi and AC Delco comparing Delphi batteries to the competition. Comparing life in different climactic regions illustrates the impact of temperature on the life of the battery.

The degree of increased application temperatures has mitigated past durability improvements to the extent that no technology has head and shoulders superiority when it comes to high operating temperature durability. Warranty experience after three years shows that very hot applications can have as much as 600% greater warranty than applications that meet the 52¡ C maximum continuous operating temperature recommended by Delphi.

Car manufacturers at first seemed oblivious to the impact of temperature on the life of the battery, but high warranty cost has made them more aware. Heat shielding has become a fairly common requirement for the battery. Improvements to positive grid alloys - increased tin in wrought calcium lead and the addition of silver to cast calcium lead - will extend the life of batteries in hot climates beyond that shown in Figure 2.

Three- and even four-year warranty policies on batteries have been put in place by automotive companies. Warranty policies are primarily a marketing issue and sometimes were made without a good understanding of battery life and the impact of temperature on battery life. These warranties have made the durability of batteries a more important requirement.

Battery role and requirements
A historical review of automotive battery requirements has shown that the role of the battery in internal combustion powered automobiles has always been that of an enabling technology. These requirements were found to be the results of the needs of:

• the electrical system;
• the vehicle's design; and
• marketing.

These needs will continue to influence future requirements and will continue to be the result of a need to make something else possible. Typically, the requirements for automotive batteries came from electrical system needs, e.g., power for cranking motors; from vehicle design needs, e.g., lower height to allow lower hood lines; and from marketing needs, e.g., maintenance free technology to make the battery transparent to the car owner.

There is, however, one easily identifiable emerging source of future requirements, i.e., the global nature of the automotive business. Automotive companies are building products globally, based on the same basic platform design. Their desire is to have the basic components, such as the battery, for these platforms the same anywhere they build in the world.

There are three primary sources for future automotive requirements. These sources are:

• market based;
• vehicle design based; and
• electrical system based.

Marketing requirements will include:

• maintaining transparency, quality, reliability and life; and
• providing a safe engine start under any conditions, including run-down protection, protected start, and "smart" batteries.

The ability to market the total car as problem/maintenance free for longer and longer times has forced the inclusion of the battery into that guarantee. Cars being advertised today are promoted as needing no major tune-ups until 100,000 miles of service. Batteries will need to have a minimum life of five years in all regions of the country to meet this type of expectation and to keep warranty costs down.

While starting failures due to run-down batteries continue to be the major battery related consumer complaint, as well as the highest battery related warranty claim item, I would not expect that a requirement of future batteries would be to fix this problem. This is an electrical system problem and will be solved as a systems solution.

Even relatively simple run-down protection approaches such as the one shown in Figure 3 that times out short term and long term loads, have been demonstrated to significantly impact the incidence of warranty claims due to run-down batteries.

The marketing desire to satisfy and protect the customer from the inconvenience of a "no start" due to a run-down or worn out battery could lead to the requirement of a "smart" battery. The combination of the computational power of automotive computers and algorithms that accurately define battery state of charge and state of health could meet this requirement.

Vehicle design requirements will include:

• Function in the engine compartment, i.e., elevated temperature durability; packaging, i.e., minimum mass and minimum volume; design for assembly; and integration of ancillary parts, i.e., tray, heat shield, etc.

A major vehicle design-based requirement will continue to be for the battery to be packaged close to the cranking motor to keep costs down. The battery will need to operate at underhood temperatures. Underhood temperatures are not expected to go much beyond those discussed earlier, but it is also expected that there will not be significant decreases in temperatures.

If grid alloy improvements are able to extend battery life, the loss of water in extreme high operating temperature applications may become the life limiting failure mode for flooded batteries. The mass of the battery has become an important requirement and will become a more important requirement in the future. This requirement will be driven by the need for fuel economy and the ability of vehicles to be designed to make desired EPA weight classes.

Automotive engineers typically define the value of reduced weight to be $1 to $2 per pound weight reduction. One manufacturer has recently set performance and mass requirements that preclude a solution with a single battery designed with current, flooded lead acid technology.

Packaging the battery under the hood continues to be a challenge. The space and system cost constraints allowed for the power and energy function may also preclude the application of a single battery designed with today's flooded lead acid technology.

Mass and volume requirements could dictate a two-battery requirement; one battery designed for maximum power to provide the power for cranking, and the other designed for capacity and cycling capability to meet running load demands. Both batteries and ancillary equipment would need to be designed to minimize weight and cost.

Assembly of the battery into the vehicle has begun to establish requirements for batteries. Most batteries are placed in position with either a robot or a mechanical assist for the assembler. These operations require physical features on the battery to allow it to be picked up by these devices.

In line with lean manufacturing concepts and design for assembly concepts, batteries may have requirements for improved assembly into the automobile with no tools, or standardized, simple tools. Ancillary parts for the automotive battery, i.e., tray, heat shield and terminal connections, may be supplied along with the battery in the form of a system. The purpose being to reduce automobile assembly cost and complexity.

Vehicle electrical systems
The primary source of requirements for the automotive battery has always been the electrical system. Any change from the current 12 volt system will generate new requirements for the battery. After the introduction of the starting motor, the design of the automotive electrical system was established by two requirements: 1) Provide power to start the engine; and 2) Provide power to electrical loads during operation of the vehicle.

Modern electronics has added a third requirement - provide power for "key off" loads such as digital clocks, computer memory, etc. Future automotive battery requirements will be, to a large extent, derived from changes in these three electrical system requirements. I see no significant changes in "key off" loads coming in the future. Automotive manufacturers implement designs to minimize these parasitic loads.

The trend in engine technology is to make engines more powerful and efficient and with lower emissions. Engine technology trends should not make engines harder to start. Reduction in engine parts friction and improved understanding of the events required to start an engine have, to some extent, lowered the electrical power required to start engines.

Major shifts in power requirements to start engines do not appear to be on the horizon. Starter motor technology does not seem to have any major changes being forecast that would impact the power requirements for the automotive battery.

There are, though, two technology developments in progress that could eliminate the need for the high power requirement for automotive batteries. The first is the ultracapacitor. An ultracapacitor can be used to supply starter current. An automotive electrical system designed with an ultracapacitor would require much lower current from the battery. The battery could then be designed accordingly.

The second development in engine technology might even eliminate the need for a starter motor. Engines are moving towards direct fuel injection to improve fuel economy and emissions. Electromechanical valve control is being developed to improve engine performance and cost.

In the future, engine valves could be electromechanically actuated as opposed to the mechanical actuation of today's engines. In theory, direct fuel injection and electromechanically controlled valves may be able to start an engine statically, with no initial rotation of the engine required. This would eliminate the high power battery requirement.

The electromechanically actuated valve is an example of the type of new electrical load that could lead to major changes in the design of the automotive electrical system. For a six cylinder engine, a peak power of 2400 watts is required to service this lead; the average power required is 800 watts.

The demand for electrical power in future automobiles continues to grow. Figure 4 shows the historical growth and the forecasted growth of automobile electrical power requirements as expressed by the instantaneous power capability of the generator. This exponential forecast rate of growth is the result of two driving forces on the electrical system - the need for improved fuel economy, and the potential new power-hungry automotive functions.

To improve fuel economy, many devices now driven directly by the engine can be more efficiently driven electrically. Some of these potential future electrical loads are shown in Figure 4.

It should be noted that most of these loads can be operated more efficiently at voltages higher than the current 12 volt system voltage used in today's automobiles. The bottom line is that in the future more electrical system power will be needed. But, that power must be used very efficiently.

Additional power can be obtained by increasing the alternator's capacity and/or the battery augmenting the alternator's output. On a car with high electrical content, it is not uncommon to have a two kilowatt output alternator. The limits of belt driven, air cooled, Lundel type alternators has about been reached at two kilowatts.

Future alternators might achieve higher output at idle speeds, but increased peak output will depend on the development of new types of machines driven by means other than belts. In effect, additional power can be obtained if the power available is used more efficiently.

Energy management systems for future automobiles are a way to more effectively utilize available power. These systems can include: allowing the charge voltage to float when the battery is at a high enough state of charge; pump energy into the battery when the car is decelerating; increase charging when engine power is available and the battery can accept charge; increase idle speed if battery state of charge is low; if battery state of charge is low shed non critical loads; and protected start capability.

The computers on board automobiles today have the control capability that will be required by future energy management systems. However, the technology that is needed to make energy management systems effective is a "smart" battery. In this case, a "smart battery" would be one that could keep the energy management system apprised of its state of charge, its temperature and its capability for accepting charge.

Higher system voltage improves the efficiency of many of the new electrical devices and of the automotive system in general by reducing resistive losses by lower required current.

To achieve this improved efficiency, the system voltage must be significantly higher than 12 volts, but for safety reasons, less than 50 volts. The industry increased system voltage in the mid 1950s. Why not again in the future?

The automotive electrical system is much more complex than it was in the 1950s. The infrastructure around 12 volt system components is large and complex. Small, economy vehicles will not utilize many of the new electrical loads. For these reasons, it is unlikely that the automotive electrical system voltage will be raised to one, higher level voltage across the industry.

In sum, using electrical power more efficiently is characterized by the following: voltages much higher than 12 volts (50 volts or less for safety) will be required; there are too many difficulties for all automotive electrical devices to be moved to one higher operating voltage; any future electrical system will be multiple voltages, most likely a dual voltage system such as 12-24 volts, 12-36 volts or 12-48 volts; and power electronics will be the enabling technology that makes dual voltage systems viable.

The alternative is to return to a multiple voltage system like Kettering's electrical system design which was a dual voltage system. At this time, the most likely system would be a dual voltage one. Systems that are 12-24 volts, 12-36 volts and 12-48 volts have been explored.

A dual voltage system is not a new approach; many heavy duty truck and off road equipment electrical systems are dual 12-24, voltage systems as the illustration from a 1957 Delco Remy training manual in Figure 5 shows. In this system, and in Kettering's system, the higher voltage was required for the cranking motor.

In future automotive electrical systems, a voltage greater than 12 volts will be required for many loads to operate efficiently, and to reduce the amount of copper needed to transmit power to loads. The multiple voltage system will be much more complex than this dual voltage one.

There have been many studies and proposed designs on potential multiple voltage systems over the past 10 to 15 years. Proposed designs have ranged from dual DC voltage levels to ones that would envision low level DC voltages and higher level AC voltages. My intent is not to establish the type and design of a new multiple voltage electrical system, but to assess the probability of such systems and the requirements such systems will impose on the battery.

If the potential for improving fuel economy by utilizing electrical energy in place of mechanical energy is to become a reality, the enabling technology will power electronics, not batteries. The efficient conversion of electrical energy to different voltage levels is a rapidly developing technology that has the potential for continuing cost reduction.

New multiple, high voltage automotive electrical systems will require cost effective power electronics to become viable. Higher voltage electrical systems using power electronic converters can be conceptualized using a 12 volt battery as the energy storage device.

In theory, new battery technology would not be required to make these multiple, high voltage electrical systems possible, but power electronics is. However, a higher voltage battery would make the task easier and is still very desirable.

In light of this information, what would one conclude the automotive storage battery beyond the year 2000 will be? The battery will need to have a minimum life of five years even while being located in the engine compartment, and it must apply in all regions of our country.

To achieve this type of life, the battery will be required to be durable at high operating temperatures and to have good life while being load cycled. The battery will need higher energy density both volumetric and gravimetric to reduce weight and to make packing easier.

The battery needs to supply a higher voltage than the current 12 volts, probably at least 36 volts. The battery needs to be able to provide information about itself, e.g., state of charge and state of life. The manufactured quality of the battery and the battery's reliability must continually improve. For those of us working to satisfy the needs of the original equipment market, it will be an interesting and challenging next 10 to 15 years as the automotive industry comes to terms with fuel economy and clean air requirements.

If I had given this presentation in 1987, it would have been very much the same as what I presented here. In the year, 2007, however, I believe it will be a new presentation - a story of dramatic changes or planned changes in the automotive electrical systems and the battery to provide that system's stored energy requirements.

Doug Barron is manager of the Freedom Battery Design & Application, Delphi Energy & Engine Management Systems, 8750 Hague Rd., P.O. Box 502650, Indianapolis, IN 466250.