Hybrid Battery Voltage Control for Start-Stop Fuel Economy
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Solution Overview
Problem
Managing energy storage systems in vehicles and stationary applications with varying service conditions and aging components to achieve optimal performance and extend battery life while improving fuel economy is challenging, especially when using battery systems with different chemistries.
Innovation Solution
A dual battery system comprising a lead-acid battery and a lithium-ion battery arranged in parallel, with a battery control module that receives data from both batteries and calculates recommended cruising voltage levels based on performance targets and operational conditions to balance fuel economy and battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single battery system is used in traditional vehicles, then the system structure is simple and easy to manufacture, but fuel economy cannot be improved and battery life is limited under advanced start-stop conditions
Solution Approach 1:
The battery system is segmented into two distinct battery modules: a first battery module (lead-acid) and a second battery module (lithium-ion). Each module serves specific functions - the lead-acid battery handles high-power transient loads like engine cranking, while the lithium-ion battery manages steady-state electrical loads. This segmentation allows the system to optimize fuel economy through intelligent energy management without requiring a complete redesign of the entire battery system.
Solution Approach 2:
The patent merges two different battery chemistries (lead-acid and lithium-ion) into a hybrid battery system. This combination leverages the complementary strengths of each chemistry - the high power delivery of lead-acid and the high energy density and efficiency of lithium-ion - to simultaneously improve fuel economy through regenerative braking energy recovery and extend overall system reliability.
2Loss of energy
If battery voltage is increased to improve fuel economy through regenerative braking, then energy recovery is enhanced, but battery life deteriorates due to increased stress and aging
Solution Approach 1:
The system dynamically changes operational parameters including voltage thresholds, charge acceptance limits, and power distribution ratios based on battery state-of-charge, temperature, and age. The control module adjusts these parameters in real-time to maximize regenerative energy capture while keeping battery stress within acceptable limits, thereby extending battery life without sacrificing fuel economy benefits.
Solution Approach 2:
The control module acts as an intermediary between the regenerative braking system and the battery modules. It manages the energy flow by determining optimal charge distribution between the two battery modules based on their respective states, preventing any single module from experiencing excessive stress while maximizing overall energy recovery efficiency.
3Productivity
If different battery chemistries are used to optimize performance, then fuel economy and energy efficiency improve, but system complexity and control difficulty increase
Solution Approach 1:
The control module continuously monitors multiple parameters including voltage, current, temperature, and state-of-charge of both battery modules, and uses this feedback to dynamically adjust power distribution and charge acceptance. This closed-loop control system automatically adapts to changing operating conditions and battery aging, simplifying the management of the dual-chemistry system while maintaining optimal energy efficiency.
Solution Approach 2:
Each battery module is managed with tailored control strategies suited to its specific chemistry characteristics. The lead-acid module receives control focused on preventing overcharging and managing high-power transient loads, while the lithium-ion module receives control optimized for maximizing energy recovery and managing steady-state loads. This localized management approach reduces overall system complexity by addressing each battery's specific needs independently.
4Duration of action of moving object
If battery capacity is increased to extend operating range, then vehicle autonomy improves, but battery weight and system cost increase
Solution Approach 1:
The system uses a composite battery architecture combining two different battery chemistries in a single integrated system. This composite approach allows the vehicle to achieve extended operating range by leveraging the high energy density of lithium-ion for range extension while using the compact, high-power lead-acid battery for immediate power needs, thereby achieving the desired operating duration without proportionally increasing total battery weight.
Data Source
AI summary
A battery system may include multiple battery cells having different chemistries. To achieve certain performance goals, voltage parameters for the battery system, such as cruising voltages and maximum voltages can be adjusted. These adjustments may, for example, direct charging currents to a lithium-ion battery to increase fuel economy or may direct charging currents away from a lithium-ion battery to increase its longevity. Methods for matching batteries having different chemistries based on their open circuit voltages are also discussed.