Virtual Energy Bucket for Traction Battery Power Limiting

Solution Overview

Problem

Frequent high power discharges in traction batteries of electrified vehicles lead to battery cell degradation, reducing their lifespan.

Innovation Solution

A system that includes a processor to set short-term and long-term power limits for the battery, adjusting the discharge limit based on the battery's charge level, and controlling charging and discharging rates to manage power usage effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high power discharge is allowed to meet power demand, then power output is improved, but battery cell degradation increases and lifespan decreases

Engineering Contradiction:

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent implements dynamic power limiting by adjusting the short-term power limit based on the battery's state of charge. The power limit is not fixed but varies dynamically according to battery conditions, allowing maximum power when charge is high and reducing power when charge is low, thus preventing degradation while meeting power demands when possible

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system continuously monitors the battery's state of charge and uses this feedback to adjust the short-term power limit. The controller receives feedback on battery charge levels and dynamically modifies the power output limits accordingly, creating a closed-loop control system that balances power delivery with battery protection

Inventive Principle:

Principle #23Feedback

2Productivity

If frequent high power discharges are allowed to meet vehicle power demands, then power delivery is improved, but battery cell degradation increases

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary action by pre-establishing short-term and long-term power limits based on the battery's state of charge before high power discharge events occur. This preventive approach sets appropriate power boundaries in advance, avoiding the need for reactive damage control after degradation has begun

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The power limits are made dynamic rather than static, adjusting in real-time based on battery charge levels. This allows the system to optimize power delivery capability when the battery is well-charged while automatically reducing power limits to prevent degradation when charge is lower, thus adapting productivity to battery conditions

Inventive Principle:

Principle #15Dynamics

3Speed

If the battery is charged at high rates to maintain charge level, then charge replenishment speed is improved, but battery stress increases and lifespan decreases

Engineering Contradiction:

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent changes the charging parameters by implementing asymmetric charge and discharge rate management. The system charges the battery at a controlled filling rate when state of charge is below the long-term power limit, and discharges at a higher depleting rate when above the limit, optimizing both charge speed and battery longevity through parameter adjustment

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10926661B2Transient battery power management

Publication Date: 2021.02.23

AI summary

A vehicle includes a processor programmed to create a virtual energy bucket for a battery, and set a short-term power limit corresponding to the virtual energy bucket that defines a discharge limit for the battery. The virtual energy bucket fills responsive to an output power of the battery being below a first power threshold and depletes responsive to the output power being above a second power threshold.