Vehicle battery monitor apparatus and method

• US 20070216407A1
• Filed: 02/27/2007
• Published: 09/20/2007
• Est. Priority Date: 03/01/2006
• Status: Active Grant

• Current Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Original Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Inventors: Yamaguchi, Kazuhi
• Granted Patent: US 7,768,266 B2
• Time in Patent Office: Days
• US Class Current: 324/256
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A battery monitor apparatus and method for an automotive battery system including a battery for supplying power to in-vehicle electrical equipment and sensors for detecting battery voltage, the charge/discharge current and the battery temperature are disclosed. The capacitance and the internal actual resistance of the battery are calculated at the time of starting the engine. Further, the theoretical internal resistance of the battery corresponding to the ambient temperature and the battery open-circuit voltage during the stationary engine state are detected in advance. Based on the change in the battery open-circuit voltage, the battery change is provisionally determined. After that, battery change or degeneration can be determined based on battery capacitance, the actual and theoretical internal resistance values of the battery, the battery open-circuit voltage and the provisional battery change determination value.

Claims

1. An automotive battery monitor apparatus comprising:

a battery capacitance calculation unit for calculating battery capacitance at the time of starting an engine;

a battery internal resistance calculation unit for calculating the actual internal resistance of the battery at the time of starting the engine;

a theoretical battery internal resistance calculation unit for calculating the theoretical internal resistance of the battery based on an ambient temperature;

a battery open-circuit voltage calculation unit for detecting an open-circuit voltage of the battery during a stationary engine state;

a battery change provisional determining unit for provisionally determining a battery change based on a change in the battery open-circuit voltage; and

a battery change determining unit for determining that the battery has been changed, based on the battery capacitance, the actual internal resistance of the battery, the theoretical internal resistance of the battery, the battery open-circuit voltage and the provisional determination of the battery change.

2. The automotive battery monitor apparatus according to claim 1,

wherein the battery change determining unit executes a battery degeneration determining process in a case where the battery open-circuit voltage has never undergone a change, the case where the battery change has never been provisionally determined and the case where the difference between the actual internal resistance and the theoretical internal resistance of the battery is less than that selected by one of a second predetermined value and a fourth predetermined value.

3. The automotive battery monitor apparatus according to claim 1,

wherein the battery capacitance calculation unit executes the process of calculating the battery capacitance also in a case where a predetermined discharge occurs during the stationary engine state.

4. The automotive battery monitor apparatus according to claim 1,

wherein the battery real internal resistance calculation unit executes the process of calculating the actual internal resistance of the battery in the case where a predetermined discharge occurs during the stationary engine state.

5. The automotive battery monitor apparatus according to claim 1,

wherein the battery open-circuit voltage calculation unit detects, a battery open-circuit voltage at the time of battery connection, the battery voltage upon lapse of a predetermined time from the establishment of the condition that the ignition key is off during the stationary engine state or in the case where the battery is disconnected and reconnected, that the battery charge/discharge current is within a predetermined range and that the other control circuits are off.

6. The automotive battery monitor apparatus according to claim 5,

wherein the battery change provisional determining unit compares the battery open-circuit voltage at the time of battery connection with a predetermined first reference voltage and based on the comparison result, provisionally determines the battery change.

7. An automotive battery monitor apparatus comprising:

a battery change detector for detecting that the battery mounted on the vehicle has been changed;

a battery internal resistance calculation unit for detecting, upon detection by the battery change detector that the battery has been changed and upon occurrence of discharge of a large current from the battery, the actual internal resistance of the battery based on the state of discharge of the large current from the battery;

a battery capacitance calculation unit for calculating the battery capacitance after the battery change based on the internal resistance calculated by the battery real internal resistance calculation unit; and

a battery charge rate calculation method changing unit for changing the method of calculating the battery charge rate based on battery capacitance calculated by the battery capacitance calculation unit.

8. An automotive battery monitor apparatus comprising:

a battery change detector for detecting that the battery mounted on the vehicle has been changed;

a battery internal resistance calculation unit for detecting, upon receipt of an engine start request and upon detection by the battery change detector that the battery has been changed, the internal resistance of the battery based on the battery discharge state at the time of starting the engine;

a battery capacitance calculation unit for calculating the battery capacitance after the battery change based on the internal resistance calculated by the battery real internal resistance calculation unit; and

a battery charge rate calculation method changing unit for changing the method of calculating the battery charge rate based on the battery capacitance calculated by the battery capacitance calculation unit.

9. A method of monitoring an automotive battery which comprises the steps of:

calculating the battery capacitance at the time of starting the engine;

calculating the actual internal resistance of the battery at the time of starting the engine;

calculating the theoretical internal resistance of the battery corresponding to the ambient temperature;

detecting the battery open-circuit voltage during the stationary engine state;

provisionally determining the battery change based on the change in the battery open-circuit voltage; and

determining the battery change based on the battery capacitance, the real internal resistance of the battery, the theoretical internal resistance of the battery, the battery open-circuit voltage and the provisional determination value of the battery change.