Parallel Battery Pack Current Limit Roll-Up for Imbalance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing battery systems for large moving work machines face challenges in managing current levels to avoid breaching operating limits, particularly due to inter-battery pack current imbalances caused by minor differences in voltage, aging, and resistance, which can lead to unsafe operating conditions under high load conditions.
Innovation Solution
A battery system controller dynamically adjusts system-level current limits by computing correction factors based on individual battery pack current ratios and proportions, accounting for inter-battery pack flows to ensure all packs operate within their limits, thereby optimizing the system's performance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery packs are connected in parallel to provide high current, then the power output is improved, but current imbalances between packs occur due to voltage and resistance differences
Solution Approach 1:
The system continuously monitors individual pack currents and voltages, computing correction factors based on measured deviations from ideal current distribution. This feedback mechanism dynamically adjusts the control strategy to compensate for inter-pack imbalances, ensuring reliable operation while maintaining high power output.
Solution Approach 2:
The system dynamically modifies operating parameters including individual pack current limits and system-level current limits based on real-time measurements of pack voltages, resistances, and currents. These parameter changes optimize current distribution across packs, preventing overheating and extending battery life while maintaining system power capability.
2Productivity
If high current is drawn from battery packs to meet load demands, then the productivity is improved, but the risk of exceeding current limits and causing overheating increases
Solution Approach 1:
The system employs dynamic current limit adjustment rather than fixed limits. Individual pack current limits are continuously updated based on real-time measurements of pack temperature, voltage, and current. This dynamic approach allows the system to safely operate at higher currents when conditions permit while automatically reducing limits when thermal or electrical stress approaches dangerous levels.
Solution Approach 2:
The control system continuously monitors pack temperatures and currents, using this feedback to adjust current limits and prevent overheating. When temperature or current approaches critical thresholds, the system automatically reduces the allowed current, preventing thermal runaway while maintaining productivity during normal operation.
3Reliability
If individual battery pack current limits are set conservatively to ensure safety, then the reliability is improved, but the system-level current capacity is reduced
Solution Approach 1:
The system merges individual pack current limits with system-level current limits to determine the actual operating current for each pack. The system-level current limit acts as an aggregate constraint that allows individual packs to contribute more current when the overall system demand is high and distribution is balanced, thereby increasing total system capacity while maintaining safety margins.
Solution Approach 2:
The system dynamically adjusts both individual pack current limits and system-level current limits based on real-time conditions. When packs exhibit good current distribution and thermal conditions are favorable, the system increases allowed currents to maximize power output. When imbalances or thermal stress are detected, limits are reduced to maintain safety, thus optimizing the trade-off between reliability and power capacity.
Data Source
AI summary
A modular battery system includes a battery bus, multiple battery packs connectable in parallel to the battery bus to provide a system current, and a battery system controller. A battery pack includes multiple battery cells and provides a battery pack current to the battery bus. The battery system controller is configured to determine whether individual battery packs are online or offline, receive individual battery pack current limits of online battery packs and set a system level current limit of the battery system, determine system current and individual battery pack currents, compare the individual battery pack currents to their respective individual battery pack level current limit, update the system current limit according to the comparing, and scale a current demand for the individual battery pack currents using proportions of the measured system current and the updated system current limit.