Battery Pack Voltage-Based Power Limit Derating
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Solution Overview
Problem
Battery packs in electric vehicles can degrade when the extracted power exceeds a desired amount, leading to operational issues.
Innovation Solution
A system and method that utilize a battery pack voltage sensor and microprocessor to determine an initial power limit based on operational parameters and adjust it by derating if the output voltage exceeds a threshold, transmitting the adjusted power limit via a communication bus to prevent degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power extraction is increased to improve productivity, then power output increases, but battery pack degradation occurs
Solution Approach 1:
The power limit is made dynamic rather than fixed. The system continuously monitors battery pack voltage and adjusts the power limit in real-time based on actual voltage conditions. When voltage exceeds the threshold, the power limit is reduced; when voltage is within acceptable ranges, the power limit can be increased or maintained at initial levels, allowing optimal power extraction without causing degradation.
Solution Approach 2:
The system implements a feedback mechanism where the battery pack voltage is continuously measured and fed back to the control algorithm. Based on this feedback, the power limit is automatically adjusted. The communication bus transmits voltage information and power limit adjustments between control units, creating a closed-loop control system that prevents degradation while maximizing power output.
2Reliability
If a fixed power limit is set to ensure safe operation, then battery pack reliability is maintained, but power output is restricted
Solution Approach 1:
The power limit transitions from a fixed value to a dynamic value that adapts to real-time battery conditions. The system starts with an initial power limit based on operational parameters, then continuously adjusts it based on voltage measurements. This allows the power limit to be higher than a conservative fixed limit would allow, while still maintaining safety through real-time monitoring and adjustment.
Solution Approach 2:
The system changes the power limit parameter based on voltage conditions. Instead of using a single fixed power limit, the system modifies the power limit parameter dynamically according to the measured battery pack voltage. When voltage is within acceptable ranges, the power limit can be set higher; when voltage exceeds thresholds, the power limit is reduced, optimizing both safety and power output.
3Reliability
If real-time voltage monitoring is implemented to adjust power limit, then battery pack degradation is prevented, but device complexity increases
Solution Approach 1:
The voltage sensor and communication bus serve multiple functions. The voltage sensor not only monitors voltage for power limit adjustment but also provides data for state of charge estimation and other battery management tasks. The communication bus handles multiple data transmissions including voltage information, power limit adjustments, and diagnostic data, reducing the need for separate dedicated components for each function.
Solution Approach 2:
The control algorithm automatically adjusts the power limit based on voltage measurements without requiring external intervention or complex control systems. The system uses its own internal sensors and processors to monitor conditions and make adjustments, making the complexity inherent to the basic battery management functions rather than adding extra layers of complexity.
Data Source
AI summary
A system for derating a power limit associated with a battery pack is provided. The system includes a battery pack voltage sensor that measures a first battery pack output voltage of the battery pack at a first time, and a microprocessor that determines an initial power limit of the battery pack based on at least one operational parameter of the battery pack. The microprocessor further determines whether the first battery pack output voltage is greater than a threshold battery pack voltage. The microprocessor further determines a first power limit of the battery pack that is less than the initial power limit, if the first battery pack output voltage is greater than the threshold battery pack voltage.


