Battery Degradation Accumulation via Mode-Specific Profiles
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Solution Overview
Problem
Modern hybrid and electric vehicles face challenges in accurately estimating the degradation and remaining useful life of their high voltage battery packs due to irreversible physical and chemical changes, which affect energy storage capacity and power, impacting vehicle performance and increasing warranty costs.
Innovation Solution
A method involving a controller that operates the traction battery based on a degradation profile, which increases according to a parameter representing total degradation, taking into account alternating storage and cycling modes, and is temperature-dependent, allowing for accurate estimation of battery life by tracking accumulated degradation over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the battery operates under alternating storage and cycling modes, then the battery provides energy storage and power delivery functionality, but the degradation accumulation becomes complex and difficult to estimate accurately
Solution Approach 1:
The patent segments the degradation estimation into separate storage degradation and cycling degradation components. The controller maintains separate accumulators for storage mode degradation and cycling mode degradation, then combines them using mode-specific fractions. This segmentation allows accurate tracking of degradation under alternating modes by treating each mode's contribution independently rather than as a single complex process.
Solution Approach 2:
The patent changes the parameter representation from simple cycle count or time-based degradation to a multi-parameter model that includes storage degradation accumulation, cycling degradation accumulation, and mode transition fractions. The degradation parameter is updated dynamically based on the current operational mode and temperature, allowing precise estimation under varying operational conditions.
2Measurement precision
If the degradation parameter increases according to temperature-dependent profiles, then the estimation accuracy improves, but the computational complexity and data requirements increase
Solution Approach 1:
The patent pre-establishes temperature-dependent degradation profiles for both storage and cycling modes before operation. These profiles contain pre-calculated degradation rates at different temperatures. During operation, the controller simply looks up the appropriate profile based on current temperature and applies it, rather than performing complex real-time calculations. This preliminary preparation reduces computational complexity during actual battery operation.
Solution Approach 2:
The patent applies partial degradation fractions when transitioning between modes rather than full degradation accumulation. The mode transition fraction (typically 0.5) represents a partial application of the previous mode's degradation contribution to the new mode's accumulator. This partial action approach provides sufficiently accurate estimation without requiring complete recalculation of all degradation factors during mode transitions.
3Reliability
If the battery degradation is tracked with high precision, then the remaining useful life can be accurately estimated, but the warranty costs and service issues may increase due to more precise failure identification
Solution Approach 1:
The patent implements a feedback mechanism where the estimated remaining useful life and degradation state are continuously monitored and can trigger alerts or warnings to operators. This feedback allows proactive maintenance scheduling and informed warranty management decisions. Rather than simply tracking degradation, the system provides actionable information that helps balance precision benefits with warranty management considerations.
Data Source
AI summary
A vehicle includes a traction battery subject to alternating cycling and storage modes and a controller. The controller is programmed to calculate an accumulated degradation for the traction battery based on a degradation profile for the traction battery. The degradation profile defines degradation accumulated over time and may differ based on the mode and temperature. The initial degradation value includes the accumulated degradation for the present mode and at least a portion of the accumulated degradation for the other mode. Degradation is then accumulated according to the degradation profile starting from the initial degradation value. The amount of accumulated degradation from the other mode that is included may vary based on the mode and the accumulated degradation.