ELECTRIC VEHICLE BATTERY PACK VOLTAGE MONITORING

• US 20150130471A1
• Filed: 11/12/2013
• Published: 05/14/2015
• Est. Priority Date: 11/12/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Bolduc, Robert J.
• Granted Patent: US 9,140,759 B2
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

Total voltage output by a multi-cell battery pack in an electric vehicle is monitored. A main microcontroller having a chassis ground is digitally isolated from positive and negative busses of the battery pack. A battery monitoring IC having a plurality of auxiliary/thermistor A/D inputs measures respective voltages of the battery cells. A voltage divider is selectably coupled to the positive bus by an evaluation switch under control of the main microprocessor with an auxiliary output terminal of the IC. A divided voltage is coupled to one of the auxiliary/thermistor A/D inputs. The battery monitoring IC transmits a digital value representative of the divided voltage output to the main microprocessor via the serial data link, and the main microprocessor determines the main battery voltage in response to the digital value.

Claims

1. An electric vehicle system, comprising:

a multi-cell battery pack providing a main battery voltage between a positive bus and a negative bus;

a main microcontroller monitoring performance of the battery pack, the main microcontroller being coupled to a chassis ground and being digitally isolated from the positive and negative busses;

a battery monitoring IC connected to the battery pack to measure respective voltages of cells in the battery pack, wherein the battery monitoring IC has an isolated serial data link to the main microcontroller to report the measured voltages, and wherein the battery monitoring IC further includes a plurality of auxiliary/thermistor A/D inputs and an auxiliary output terminal selectably providing a drive signal;

an evaluation switch having an input, an output, and a control terminal, wherein the input is connected to the positive bus, and wherein the control terminal is coupled to the auxiliary output terminal so that the evaluation switch is activated in response to a command received from the main microprocessor over the serial data link; and

a voltage divider coupled between the output of the evaluation switch and the negative bus and providing a divided voltage output to one of the auxiliary/thermistor A/D inputs;

wherein the battery monitoring IC transmits a digital value representative of the divided voltage output to the main microprocessor via the serial data link, and wherein the main microprocessor determines the main battery voltage in response to the digital value.

2. The system of claim 1 wherein the voltage divider is comprised of a high side resistor coupled in series with a low side resistor, wherein a junction between the resistors provides the divided voltage output which is coupled to the auxiliary/thermistor A/D input, and wherein the system further comprises a reverse voltage blocking diode coupled between the evaluation switch and the high side resistor.

3. The system of claim 2 further comprising a filter coupled between the auxiliary/thermistor A/D input and the junction between the high side and low side resistors.

4. The system of claim 1 further comprising a thermistor mounted for sensing a temperature of the battery pack and coupled to an A/D conversion input of the main microprocessor and to the chassis ground.

5. An electric-vehicle battery monitoring method comprising:

digitally isolating a main microprocessor from a battery monitoring IC;

selectably coupling a voltage divider between a positive bus and a negative bus driven by a multi-cell battery pack;

digitally sampling a divided voltage using an auxiliary/thermistor input of the IC;

transmitting a digital sample to the main microprocessor via an isolated serial data link;

evaluating the digital sample to determine an output voltage of the battery pack.