Current Problems with Automotive Electrical Power.

Transcription

1 Current Problems with Automotive Electrical Power. Hybrid car designers also need accurate current datalogging capabilities. By accurately measuring how efficiently experimental batteries store and deliver an electrical charge, it is possible to predict how many times battery cells can be charged and discharged - the cycle life of the battery. Trying to predict how long a battery will last on the shelf is known as calendar life. Combined, cycle life and calendar life determine how long a battery will be useful - essential for determining battery-pack specifications to be able to store the advertised amount of energy throughout the life of the car. A key measurement of battery quality is the difference between the amount of charge that goes into a battery during charging and the amount that comes out when it's discharged (called coulombic efficiency). If less charge comes out than goes in, then energy is being wasted by unwanted chemical reactions in the battery. A frequent cause of conventional car breakdowns is a flat or defective battery. One reason for this is the ever increasing number of electrical loads in vehicles. Automotive manufacturers are constantly striving to meet challenges of increasingly complex electrical systems and minimizing battery problems. A key objective is to accurately measure electricity consumption in vehicles under real-world conditions, including the demands of climate change requirements. These measurements need to be accurate over an extremely wide range - from ma to hundreds of amps. The 15-bit resolution KLARI-MOD and KLARICORD measurement modules to log electrical system performance in the design phase to reduce power consumption, as well as in manufacturing test for quality control purposes. These versatile little boxes are also useful for wide-ranging current measurement needs other than automotive-based applications. Intelligent KLARI-MOD MC 2 modules are a new generation of electronic measurement equipment. Two galvanically isolated inputs, both equipped with their own ASIC, allow a very flexible measurement of currents and voltages in the vehicle. Each ASIC uses 5 internal measurement ranges which are able to convert input signals from ±7.5 to -300/+720 mv with a resolution of ±15 Bit. The input signal amplifier is integrated internally, so external amplification is not required. With the selectable Autorange mode, the measurement ranges can be adapted to the measured values without operator input. The sampling period for each ASIC is adjustable in steps between 250µs and 128ms. During the sampling period, all measured values are integrated, averaged and output as one value. The measurement module is configurable via a serial RS232 or USB interface. The data output can be via CAN and/or RS232. In order to limit the data volume, data reduction without losing information are available. The data transmission via CAN is individually configurable and additionally enables the time synchronization of a couple of modules. KLARI-MOD MC 2 can be adapted to the measuring task individually by selecting various current, voltage and temperature probes. A 6-contact push-pull-connector is used for connecting the measuring probe to the module.

2 The automatically probe identification enables the plug & play functionality as well as the transmission of probes calibration data to the module. Thus, the measured values are calculated and output correctly anytime without input of correction factors. A small and robust housing (35x60x100mm) and a number of available probes for current, voltage and temperature make KLARI-MOD MC 2 suitable for all measurement tasks in the automotive world. Typical applications for KLARI-MOD MC 2 are: Automotive testing measuring of start-, operating- and sleep current as well as voltage in the vehicle (automobile & truck), current measurement range e.g.: A; resolution of 1.25 ma/bit (measuring shunt 200 µohm). Electronic development measuring of operating- and sleep current as well as voltage of single electronic modules, current measurement range e.g.: -0, A; resolution of 0.5 µa/bit (measuring shunt 500 mohm). Operating and quiescent current measurement The measurement of currents and voltages is already in the early stages of development an integral part of vehicle the testing program, and accompanies the development process through all the stages through to production release. In the initial phase of development, the individual components and their interaction in terms of power consumption not yet been optimized. Quiescent current measurements with a high measurement resolution are not useful here feasible because sometimes can flow more 10 A. Only in later stages of development, a level of consumption reached at which meaningful measurements quiescent current be carried out, to "black sheep" to. For measurements on the complete vehicle to the car manufacturer Also, the measurement modules KLARI-MOD and KLARICORD The Stuttgart-based company Stefan Klaric one. Counterpart the previously used measuring technique, in which different Shunts depending on the expected current in the measurement path were switched, these modules the entire vehicle in the typically occurring current range with a shunt measuring results (Table 1). The measured resistance is extremely low with 200 μω, to influence the voltage level as little as possible. The ASIC has used with over 4 ranges a resolution of 16 bits, in the auto range mode are automatically adapted to the respective measurement. A microprocessor takes over, depending on the Measured value, the Range ASIC switching, processing and the output of the measured values. Both module types have 3 channels, which selectively, in addition to the current, either 2x voltage (eg, battery and Generator voltage) or 1x and 1x voltage temperature Figure 2: KLARI-FUSE measurement

3 modules in the test vehicle. While KLARI-MOD to the measurement data via a PC CAN or external logger max. approximately 1,000 sample pairs / s outputs KLARI-CORD is for long-term measurements with low specific power consumption and integrated Data memory (SD card) and optimized is in addition to the battery accounting. Measurement modules in the test bed For the analysis of individual consumers or circuits the test vehicle (vehicle) attack the Automobile manufacturers often KLARI-FUSE back, a millivolt meter with 8 parallel, mutually variable sensitivity. On all inputs Different probes for electricity Voltage and temperature measurements connected be. These probes are the Measurement module is automatically identified. To assist in the Measurement calculation highest possible To achieve accuracy, the calibration of each sample is transferred to the measuring module and used for the calculation. The measurement data be via CAN and / or RS232 interface transmitted per channel output up to 480 samples / s. Various configuration options allow for example, the operation of several modules in the Master-Slave Mode, or the reduction of the volume of data on different operating modes and the averaging of measured values. These modules are preferably in the interior of the vehicle mounted and, for example, directly from the Vehicle fuse box looped into an electrical circuit (Fig. 2). To the extremely expensive testbed against possible To protect short circuit, the measuring circuits here by the original vehicle security protected. The arrangement of the measuring shunts in a separate enclosure ensures that the Readings are not distorted by thermal effects be. For laboratory measurements on cars where the electronic complete electrical / System using the original Harnesses in a so-board assembly is simulated, does this measurement also used. Together with the current and voltage readings are often a number of other metrics added that with the help of a commercially available Software metrics are evaluated. The transfer of KLARI-MOD and KLARI-FUSE-readings with its own, from the CAN bus independent timestamp allows the temporal allocation of the measured values and the correlation with other data. Through this high-resolution measurement, the exact measurement of electrical quantities in allows very large areas, can also smallest "power hungry" to be identified. Up to 80 ECUs in a vehicle of the premium is themselves in this way a substantial optimization potential. Earlier for closed-circuit analysis, a 20-A shunt was inserted of the high starting currents with a change- Figure 3: Quiescent current measurement before / after. Table 1: Current measurement range, resolution KLARI-MOD and KLARI-CORD 750 A. Figure 1: Battery margins in the 10-year comparison. (Source: ADAC Breakdown Statistics 2006) Gain Range Resolution / -750 A ma 24 + / -150 A 4.58 ma 50 + / -75 ma 2.29 A / A 1.14 ma ter had to be bridged. Was to record A separate logger used (see Figure 3). The last few Years used KLARI-CORD modules have with

4 a 200 μω shunt a measuring range of max. 750 A at a resolution of about 1 ma. They enable the Detecting the starting currents and the recording of the sleep and resting behavior with only one measuring module (images 4 and 5). In addition, the recorded KLARI-CORD Battery charge, discharge and total balance sheet and has an SD card as an integrated data storage (up to 2 GB sufficient for max. ) about 450 days of recording time. With a sampling rate of 1 sample pair / s, the Data volume about 4 MB/24h, the internal current consumption is at approximately 3 ma. Sample at 100 pairs / s increases the volume of data to about 40 MB/24h, the module requires its approximately 7 ma. In this example, the starting currents are about 470 A, the quiescent current at about 10 to 13 ma. Battery on accounting transit For a long time for the vehicle manufacturer is not transparent, what conditions the battery and electrical system for long Overseas shipments were subject to, such as when vehicles were shipped to Japan or the U.S.. Meters, the remaining battery capacity in ampere hours Have recorded (Ah) gave, as an indication as to whether the battery capacity was claimed unduly but provided no information on the nature and timing of Load as well as the battery voltage. In order for the Transport until the arrival of the vehicles at the dealership sufficient battery capacity for the motor starts to To have been available, battery on these vehicles Breaker installed, the battery from the electrical system of disconnect. As part of quality assurance were in single Vehicles KLARI-CORD installed measurement modules powered by a separate battery and have been on the entire transport battery current and voltage and Batterielade-/Entladedaten, each with a precise Timestamps are recorded. In this way could secure Gained the knowledge about how long the actual journey time was when and how often a vehicle on the way to Dealer was started and how long the engine is gone was like Einschlafverhalten the electronics and how The electronics are often woken up how much sleep the current was Board Etzel Automotive l45 Figure 4: Acceleration measured by one Klari recordset module. which battery capacity and voltage at end of transport available stood. These data had the character of a Transport diary and led to that, depending on the destination and vehicle model on the installation of the battery master switch could do without (Fig. 6). Analysis of problem vehicles In the analysis of problem vehicles is the above-described Measurement is also used: In Final production test, vehicles are a "quick sleep mode" in put to sleep, electricity and Voltage via the integrated Battery sensor measured. Corresponds to the Vehicle in terms of sleep and Quiescent current level not within specification,

5 is a comprehensive failure analysis, possibly by also several days. This secured that no vehicle production leaves when the existing on-board network Specifications are not met. The same applies to "stay-chairs" in the field: the vehicles can regard with the KLARI-CORD modules its current characteristics are analyzed in detail. For this purpose are sometimes longterm measurements over several Days and weeks performed to the power consumption to capture the entire vehicle, and in the next step about measurements on individual consumers in the vehicle problematic components out. Conclusion The accurate detection of operating and quiescent currents in Vehicle, in particular the Einschlafverhalten and Current profile in the sleep phase, provides design engineers a lot of information about the vehicle and these assemblies Electrical / Electronics. By Knowledge of the behavior of the individual controllers can from an unusual overall current profile on the often erroneous Controller will resign. The electrical system poses for the automotive engineers in the next Years still some challenges. A Reduction of the electrical load is not to be expected new functionalities to reduce fuel consumption, as the start-stop system have, in turn, significant impact on the electrical system - the number of motor starts rising, at the same time reduces the duration of the generator. Car manufacturers and their suppliers have also in recent years, a variety of effective Measures taken, in spite of the electrical system increasing number of consumers to make reliable. As examples may be mentioned here: the battery state detection - A battery sensor with integrated processor captures the basic battery sizes tension Current and temperature and calculates quantities that the Condition of the car battery describe. In conjunction with an intelligent battery management is on the one hand the starting capability of the battery obtained, on the other hand can a generator management a more real to the As tailor made power generation be. The two-battery electrical system (a "start memory") is purely for the starting process optimized, while a "battery supply" provided for the electrical system (no starter) is. Thus, do not pollute the rest of the current consumer Start memory. Via the on-board control unit at Requirements connected both wiring areas together be. The most sustainable measure is the reduction the power consumption of all electrical and electronic Components in the vehicle. Not least in the Terms of climate protection, because 100 for the production of W of electrical power in the vehicle must be approximately 0.17 liters of fuel are used per 100 km. This requires a highresolution measurement, such as KLARI-MOD, KLARI-CORD and KLARIFUSE Modules produced by Klaric. In order to be electrical Sizes, both at the individual consumer as well as in Total vehicle, exactly detected, the search for "energy guzzlers" is effectively supported.