Parallel Battery Pack Control for Inrush Current Prevention
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Solution Overview
Problem
Large moving work machines require a large mobile electric energy source, and connecting multiple battery cells in parallel can lead to high inrush currents if they have uneven state of charge, potentially damaging the batteries and other components.
Innovation Solution
A modular battery system with a system controller circuit and pack controller circuits that manage the online activation of battery packs and strings, ensuring that only the pack with the highest offline voltage is brought online first, and subsequent packs are activated when their voltage is within a predetermined threshold of the load voltage to prevent inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery cells are connected in parallel to provide sustained energy power, then the power and energy capacity are improved, but high inrush currents occur when battery cells have uneven state of charge, causing potential damage
Solution Approach 1:
The system performs preliminary voltage assessment of all battery packs before connecting them to the load bus. The controller identifies packs with voltages within a predetermined threshold of the load voltage and connects them first, while waiting for other packs to reach acceptable voltage levels. This preliminary action prevents inrush currents by ensuring voltage compatibility before parallel connection.
Solution Approach 2:
The system dynamically adjusts the connection timing of each battery pack based on real-time voltage measurements. Instead of connecting all packs simultaneously or in a fixed sequence, the controller continuously monitors voltages and connects packs as they become ready (within voltage threshold), creating a dynamic, adaptive connection process that prevents harmful inrush currents.
2Productivity
If multiple battery packs are brought online simultaneously, then the productivity and power delivery are improved, but the risk of damage from voltage imbalance increases
Solution Approach 1:
The controller performs preliminary voltage checks and identifies ready-to-connect battery packs before initiating parallel connection. This preliminary assessment ensures that only packs with compatible voltages are connected simultaneously, maintaining reliability while enabling efficient power delivery.
Solution Approach 2:
The system continuously monitors the voltages of all battery packs and uses this feedback to determine connection timing. The controller adjusts the connection sequence based on real-time voltage information, ensuring that packs are connected at optimal moments to maintain system reliability while maximizing productivity.
3Adaptability or versatility
If battery packs with different voltages are connected in parallel, then the system becomes more adaptable to different power requirements, but the risk of current damage and battery damage increases
Solution Approach 1:
The system dynamically determines the adaptability of battery pack connections based on real-time voltage conditions. Instead of having a fixed connection configuration, the controller adjusts which packs are connected and when, based on voltage compatibility. This dynamic approach maintains adaptability to different power requirements while preventing current damage through intelligent voltage-based decision-making.
Data Source
AI summary
A method of operating a machine battery system having multiple battery packs connectable in parallel includes bringing a first battery pack with the highest offline pack voltage online for discharging, including a pack controller circuit of the first battery pack bringing one or more individual battery strings of the first battery pack online; bringing a next battery pack with a next highest offline pack voltage online when the next highest offline pack voltage is within a predetermined discharge threshold voltage of a load voltage, including the pack controller circuit bringing one or more individual battery strings of the next battery pack online; and waiting to bring the next battery pack online, when the next highest offline pack voltage is less than a predetermined discharge threshold voltage of the load voltage, until the next highest offline pack voltage is within the predetermined discharge threshold voltage.