In-vehicle battery monitor
An apparatus and a method of monitoring a battery in an automotive vehicle are provided. An output is provided which can be a relative output as a function of minimum and maximum parameters of the battery.
1. A battery monitor for monitoring a battery of an automotive vehicle, comprising:
a voltage sensor configured to monitor a voltage across the battery;
a current sensor configured to monitor an electrical current through the battery;
an analog to digital converter configured to convert sensed current from the current sensor to a digital value;
a constant offset configured to reduce a quiescent current draw from the sensed current prior to digitizing the sensed current by the analog to digital converter; and
a processor configured to measure a parameter of the battery as a function of sensed current and sensed voltage.
2. The apparatus of claim 1 wherein the processor enters a sleep mode during periods of vehicle inactivity and is activated from the sleep mode if current is greater than at least the constant offset.
3. The apparatus of claim 1 wherein the constant offset has a first value during vehicle operation and a record value during vehicle inactivity.
4. The apparatus of claim 1 wherein the processor integrates digitized current values over time.
5. The apparatus of claim 1 the processor uses the constant offset for calculations of the digitized current is less than a threshold.
6. The apparatus of claim 1 , including:
a communication link configured to couple to a data bus of the vehicle; and
wherein the processor is further configured to receive a signal from the data bus indicative of operation of an electrical component of the vehicle and responsively wake up from a sleep mode to monitor the electrical current through the battery using the current sensor.
7. The apparatus of claim 6 wherein the processor re-enters the sleep mode after operation of the electrical component has terminated.
8. A battery monitor for monitoring a battery of an automotive vehicle, comprising:
a current sensor configured to monitor an electrical current through the battery;
a communication link configured to couple to a data bus of the vehicle; and
a processor configured to receive a signal from the data bus indicative of operation of an electrical component of the vehicle and responsively wake up from a sleep mode to monitor the electrical current through the battery using the current sensor.
9. The apparatus of claim 8 wherein the processor re-enters the sleep mode after operation of the electrical component has terminated.
10. The apparatus of claim 8 wherein the signal indicates a door of the vehicle has opened.