Vehicle Battery Open-Circuit Voltage Profile Determination
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Solution Overview
Problem
Vehicle battery management systems face challenges in accurately determining the open-circuit voltage profile due to aging effects, which affect charging state and capacity calculations, and existing methods require additional hardware and skilled personnel.
Innovation Solution
A method and device that completely discharge and charge the vehicle battery using internal loads and a charging device, sensing voltage profiles during these processes, and determining the open-circuit voltage profile through weighted interpolation, without requiring additional hardware or personnel, allowing for precise calculations and compensation of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the open-circuit voltage is measured using the GITT method with small current amplitude, then the measurement precision increases, but the measuring time increases significantly
Solution Approach 1:
The patent performs complete discharging and charging cycles to establish the open-circuit voltage profile in advance. By pre-determining the voltage profile at different state of charge levels through full charge-discharge cycles, the system avoids time-consuming small-current measurements during normal operation. The weighted interpolation of voltage profiles from complete cycles provides accurate open-circuit voltage values without requiring prolonged measurement periods.
2Measurement precision
If the open-circuit voltage profile is determined through complete charge and discharge cycles, then the determination accuracy improves, but the time required for determination increases
Solution Approach 1:
The patent uses feedback by continuously monitoring the actual state of charge during charge and discharge cycles and comparing it with the predetermined open-circuit voltage profile. The weighted interpolation method incorporates feedback from both charging and discharging voltage profiles, allowing the system to accurately determine open-circuit voltage at any state of charge without repeating complete cycles. This feedback mechanism enables the system to maintain high determination accuracy while reducing the frequency of complete charge-discharge cycles.
3Reliability
If additional hardware and skilled personnel are used for open-circuit voltage measurement, then the measurement reliability improves, but the device complexity and operational difficulty increase
Solution Approach 1:
The patent implements self-service by using the vehicle's existing battery management system components to perform complete charge and discharge cycles and calculate the open-circuit voltage profile. The system utilizes already-present sensors, charging infrastructure, and control units to automatically execute the measurement protocol and perform weighted interpolation calculations. This eliminates the need for additional specialized measurement hardware and reduces dependency on skilled personnel, as the system autonomously determines its own voltage profile using standard vehicle components.
Data Source
AI summary
The present invention relates to a method and to a battery management system which are suitable for determining an open-circuit voltage profile (3) of a vehicle battery, dependent on a state of charge, in a vehicle. In this context, the following occur: complete discharging (S1) of the vehicle battery by vehicle-internal loads of the vehicle, sensing (S2) of a first sensed, state-of-charge-dependent voltage profile (1) during the discharging (S1) of the vehicle battery, complete charging (S3) of the vehicle battery by a charging device, sensing (S4) of a second sensed state-of-charge-dependent voltage profile (2) during the charging (S3) of the vehicle battery, and determination (S5) of the state-of-charge-dependent open-circuit voltage profile (3) by means of a weighted interpolation of the first sensed voltage profile (1) and of the second sensed voltage profile (2).