Lithium-Ion Cell Warm-Up Using Bidirectional Current Cycling
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Solution Overview
Problem
Lithium-ion batteries experience significant performance degradation at sub-zero temperatures, leading to reduced discharge capability and increased energy loss, which is not adequately addressed by existing warm-up techniques.
Innovation Solution
A predictive control-based method that utilizes bi-directional currents to efficiently warm up lithium-ion batteries by optimizing current magnitude and regulating energy loss, leveraging an auxiliary energy storage element like an ultra-capacitor to minimize energy dissipation and achieve desired power capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external heating elements or jacket heating are used to warm up lithium-ion cells at sub-zero temperatures, then the cell temperature increases, but the energy loss increases and the heating efficiency decreases
Solution Approach 1:
The lithium-ion cell heats itself by utilizing its own pulse power capability through bidirectional current cycling. The cell acts as both the heating source and the object to be heated, eliminating the need for external heating elements. This self-heating approach reduces energy loss because the heat is generated internally where it is needed, rather than being transferred from an external source.
Solution Approach 2:
The patent employs periodic bidirectional current cycling (charging and discharging phases) to generate heat through internal resistance. The periodic nature of the current reversal creates repeated heating cycles that efficiently raise the cell temperature while allowing for thermal management and preventing overheating.
2Productivity
If bidirectional currents are used to warm up lithium-ion cells, then the warm-up efficiency increases, but the device complexity increases due to the need for auxiliary energy storage elements
Solution Approach 1:
The auxiliary energy storage element (ultra-capacitor or another battery) serves multiple functions: it provides the bidirectional current cycling capability, stores energy for the charging/discharging cycles, and can be integrated into the existing battery system architecture. This multi-functionality justifies the added component by providing several benefits from a single addition.
Solution Approach 2:
The auxiliary energy storage element acts as an intermediary that enables the bidirectional current flow without requiring complex external power sources or heating equipment. It mediates between the available power sources and the lithium-ion cell, simplifying the overall system architecture while achieving efficient heating.
3Temperature
If the cell is warmed up to a pre-specified temperature, then the temperature threshold is met, but the performance degradation at sub-zero temperatures is not fully addressed
Solution Approach 1:
The patent uses pulse power capability (state-of-power) as a feedback metric to determine when warm-up is complete, rather than relying solely on temperature thresholds. The controller continuously monitors the cell's power capability and adjusts the heating process accordingly, ensuring that the cell reaches the required performance level for cold-weather operation.
Solution Approach 2:
The patent changes the control parameter from temperature-only control to power capability-based control. By monitoring and responding to the cell's actual power delivery capability rather than just its temperature, the system ensures that the cell is truly ready for cold-weather performance requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces energy loss by up to 20% and allows for longer warm-up times, enabling the widespread use of lithium-ion batteries in cold conditions without performance degradation, suitable for electric vehicles and other applications.
Implementation Method 1
Heat generated being proportional to the input current, the candidate current profile is selected to be bi-directional to minimize cumulative discharge and achieve fast warm-up
Data Source
AI summary
There is disclosed an electrical device and a method in which a battery is warmed up when operating from a sub-zero temperature. The electrical device may include a battery; an electrical storage element; and a battery management system including a controller in electrical communication with the battery and the electrical storage element. The controller can be configured to execute a program stored in the controller to shuttle energy between the battery and the electrical storage element until a power capability threshold of the battery has been reached, Shuttling the energy raises a temperature of the battery to meet power demand.