Retired EV Battery SOC Mapping for Capacity-Imbalance Control
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Solution Overview
Problem
Electric vehicle (EV)-retired batteries exhibit differential state of health (SOH) deterioration at varying rates, posing challenges for their direct reuse in stationary battery energy storage systems (BESS) due to capacity imbalances.
Innovation Solution
Implementing a control objective map (COM) to derive a mapping between the state of charge (SOC) of each battery unit relative to the average SOC, using DC to DC power converters to connect battery units to a shared bus, with a current reference for each unit to manage capacity differences and extend battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If EV-retired batteries are directly reused in stationary BESS, then energy storage capacity is provided, but capacity imbalance and differential SOH deterioration occur
Solution Approach 1:
The patent applies local quality by implementing individualized SOC trajectories for each battery unit based on its specific capacity and SOH characteristics. Each battery unit is assigned a customized charge-discharge profile rather than a uniform control strategy, allowing the system to accommodate capacity imbalances while maintaining overall system reliability and extending the operational life of retired EV batteries in stationary BESS applications.
2Ease of operation
If uniform charge-discharge control is applied to all battery units, then system operation is simplified, but batteries with different capacities experience accelerated SOH deterioration
Solution Approach 1:
The patent implements dynamic control by continuously adjusting individual battery unit SOC trajectories based on real-time monitoring of capacity and SOH parameters. The control system dynamically modifies charge-discharge rates and SOC ranges for each battery unit, enabling adaptive life extension strategies that respond to changing battery conditions while maintaining manageable system operation through automated control algorithms.
3Duration of action of stationary object
If individualized SOC control is implemented for each battery unit, then battery life is extended, but system complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying key operational parameters such as SOC ranges, charge-discharge rates, and trajectory profiles for each battery unit based on their capacity and SOH characteristics. This approach enables life extension through parameter optimization rather than hardware modification, managing system complexity through software-based control while achieving extended operational life for retired EV batteries in stationary BESS applications.
Data Source
AI summary
An apparatus for extending battery life includes a control objective map module configured to derive a mapping between a state of charge (“SOC”) of each battery unit of a plurality of battery units with respect to an average SOC of the battery units. A highest capacity battery unit has a highest discharge amount between a SOC maximum and a SOC minimum and a lowest capacity battery unit has a lowest discharge amount between the SOC maximum and the SOC minimum. Each battery unit is connected to a shared bus through a direct current (“DC”) to DC power converter. The control objective map provides a current reference for a battery unit of the plurality of battery units in relation to a common current of the shared bus. The current reference for the battery unit includes a reference current for the DC to DC power converter connected to the battery unit.