Technique Using a Battery Charger and Battery Management System to Detect Cell Degradation and Pack Imminent Failures
An Energy Management Unit (EMU) integrates the on-board charger (OBC) and battery management system (BMS) and optional DC-DC to behave like a lab based Electrochemical Impedance Spectroscopy (EIS) device. New high-bandwidth charge control schemes, together with new high-voltage system architecture, are disclosed. During vehicle AC charging, the OBC outputs current that sweeps across various frequencies (typically 0.1 Hz to 10 kHz), while the BMS samples the voltage and current to create the Nyquist Plot (Real Vs Imaginary Impedance) of battery cell parameters, without high frequency cell voltage samples (which is not cost feasible for mobility and energy storage applications).
1 . An Energy Management Unit (EMU) which combines a battery management system (BMS) and On-Board Charger (OBC) and optional DC-DC for managing a battery comprising:
a plurality of communications to Analog Front End (AFE) application-specific integrated circuit (ASICs) and current sensors, and
a power-electronics assembly designed to take AC grid power and charge the battery.
2 . The EMU of claim 1 , wherein the OBC comprises a low output capacitance charger.
3 . The EMU of claim 1 , wherein one or both of DC outputs of the OBC are connected to a battery side of main contactors of the battery.
4 . The EMU of claim 1 , wherein only one DC output of the OBC is connected to a battery side of main contactors of the battery while maintaining functional safety against over-charge while being able to measure a battery frequency response without the signal being altered by a DC bus capacitance.
5 . The EMU of claim 1 , wherein the OBC is configured to control an output current at various sinusoidal frequencies.
6 . The EMU of claim 1 , when the OBC is configured to output current of various sinusoidal frequencies, when one or more of main contactors of the battery are in open state.
7 . The EMU of claim 1 , wherein the charger is configured to control DC pulses and directly measure the high voltage battery and/or low voltage battery power available.
8 . The EMU of claim 1 , wherein synchronized samples of battery current and voltage are acquired through the AFE ASICs and the current sensor, when the OBC is configured to output current of various sinusoidal frequencies.
9 . The EMU of claim 1 further configured to compute battery impedance (magnitude and phase angle) of various frequencies, and re-create a Nyquist Plot data and parameters.
10 . The combined EMU of claim 8 , wherein the OBC is configured to synthesize an output waveform via frequency adjustable sine wave/sawtooth generator, internally track angle and send analog to digital converter (ADC) sample commands depending on a corresponding output angle.
11 . The EMU of claim 1 , wherein parameters are extracted to fit various battery models comprising 2RC model.
12 . The EMU of claim 9 wherein the OBC is further configured to trigger a BMS ADC sample request via a hardwired output/input interrupt.
13 . The EMU of claim 1 , wherein parameters are extracted to indicate an imminent cell short failure, via phase angle analysis and cell anomaly
14 . The EMU of claim 12 , wherein the BMS is configured to use an input interrupt to trigger isoSPI/current sensor start of a conversion command; and
wherein, after each ADC conversion is complete and BMS is ready, the OBC is configured to send a next sample trigger theta(n)=theta(n−1)+d_theta.
15 . The EMU of claim 1 , wherein the OBC is configured to communicating to the BMS of its output current frequency
16 . The EMU of claim 1 , wherein voltages are sampled at a lower frequency and then stitched together to recreate a higher frequency signal.
17 . The EMU of claim 1 further wherein the EMU allows improved measurements of State of Charge, State of Health and State of Power.
18 . The EMU of claim 1 further comprising a low-voltage battery charger that converts power form a high-voltage battery and charge a low-voltage battery.
19 . The EMU of claim 17 , wherein the low-voltage battery charger comprises a DC/DC converter.
20 . The EMU of claim 17 , wherein the EMU allows current injection of various frequencies into the low-voltage battery, and extracts battery parameters to indicate an imminent cell short failure, via phase angle analysis.