1. Technical Field
The technical field relates generally to monitoring the connections between a motor vehicle electrical system and a battery.
2. Description of the Problem
Electrical systems for internal combustion engine based motor vehicles include electrical loads, generators or alternators for generating electricity, rechargeable batteries for storing electrical power potential in chemical form and distribution wiring including power buses. Cabling and clamps which connect the electrical system, particularly the generator or alternator, to the vehicle battery are subject to coming loose or otherwise failing. Loss of connection from the alternator to the battery can lead to discharge of the battery. A resulting reduced state of charge may be insufficient for later restart of the vehicle and deep discharge of the battery can result in damage to the battery.
Battery clamp monitoring and testing is known. U.S. Pat. No. 3,889,248 provided a faulty battery connection indicator that included a high resistance indicator lamp and fuse connected between cabling and a battery terminal parallel to a battery clamp. Increased resistance due to corrosion between the terminal and clamp resulted in increased current flow through the indicator lamp, resulting in light emission, and increased cumulative current through the fuse which opened the fuse indicated excess corrosion. U.S. Pat. No. 6,667,624 provides connection testing apparatus incorporated into a battery charger.
A motor vehicle electrical power system provides monitoring of the connection between a vehicle battery and a direct current power source for charging the battery. A voltage transient detector determines if voltage levels on the connection between the vehicle battery and the direct current power supply exceed a minimum threshold. Additionally, a timer or low pass filter passes only those voltage transients which exceed a minimum duration. Responsive to detection of a voltage transient exceeding the minimum threshold and minimum duration, a load dump event is signaled indicating a possible transient interruption of the connection between the vehicle battery and the direct current power source has occurred. The occurrence of such voltage transients serves as criteria indicating a loose or failing battery to direct current source connection.
Referring to
Incipient problems in the connection between alternator 20 and chassis battery 12 may first occur as intermittent interruptions of the connection between alternator 20 and chassis battery 12 due to vibration from operation of the vehicle or heating and cooling of cabling 18. During operation of thermal engine 14, when alternator 20 is generating power, interruptions in the connection between chassis battery 12 and alternator 20, or between either component and chassis ground, interrupts the charging circuit from alternator 20 to battery 12. Due to the inherent inductiveness of the alternator 20, these interruptions produce a “load dump” transient voltage spike on the cabling 18 connecting the alternator 20 to battery 12. This transient voltage spike rises from the normal battery voltage of about fourteen volts up to a voltage of much greater than fourteen volts. Such transient voltage spikes can be detected using a voltage sensor 36 connected to cabling 18. Voltage sensor 36 provides a voltage measurement to an engine control module (ECM) 32 or, alternatively, to a body controller 30. Appropriate analog to digital conversion of the measurements may be incorporated in the ECM 32, body controller 30, some other microcontroller, or the voltage sensor 36.
ECM 32 is illustrated as connected to a voltage sensor 36 which monitors the voltage on battery positive terminal 12A of chassis battery 12. Normally the ECM 32 would be used to provide a J1939 message that a voltage transient has occurred. Body controller 30 is an electronic control system element which can be programmed to analyze the voltage measurement signal to determine if interruptions in the connection between alternator 20 and chassis battery 12 are occurring. Although the signal to the body controller 30 over the serial datalink 40 is usually heavily filtered by the ECM 32 software, and the body controller would not be able to read specific occurrences of voltage transients from J1939 messages, the body controller is itself an electrical load power from the DC power bus 16 and can perform its own monitoring of voltage levels on the battery terminals 12A, 12B. If voltage transient spikes consistent with interruption of the alternator 20/chassis battery 12 circuit are occurring, indication of such may be passed to a gauge controller 42 for generation of a warning on a cab display 44. This can be done before the connection is lost completely or seriously compromised. In other words, such a failure is “predicted” in time for preventive maintenance, which also stems possible damage to electrical loads 46 connected to direct current power bus 16 from voltage transients.
The distribution of functions between ECM 32 and body controller 30 is given as an example only, and the functions could be differently, including on controllers not shown. One such implementation could be to provide a direct digital implementation with an analog to digital (A/D) converter built converter built into the body controller 30, possibly with addition of a voltage divider circuit ahead of the A/D converter. The timing window would then be built into the sample and compare cycle. For example, five samples exceeding the (voltage divided adjusted threshold) voltage in a 20 sample rolling window (first in, first out) with a 10 millisecond space between consecutive samples
While it is contemplated that the detection functions be carried out using an existing voltage sensor 36 and vehicle controllers, the functionality can be realized, or represented, in analog circuit elements.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US10/35186 | 5/18/2010 | WO | 00 | 10/25/2012 |