Parallel Battery Branches with Low-Resistance Cells
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Solution Overview
Problem
Series-connected battery modules in energy storage systems for electric vehicles are prone to failure and power reduction due to temperature-dependent internal resistance, requiring energy-intensive and time-consuming heating for low-temperature operations.
Innovation Solution
An energy storage device with parallel energy supply branches, each containing series-connected energy storage modules with switchable coupling devices, utilizing specialized cells with lower internal resistance at low temperatures for rapid power delivery, and optional heating elements for further temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery cells are used in series connection to meet power and energy requirements, then the power and energy capacity is improved, but the system reliability deteriorates because a single cell failure causes entire line failure
Solution Approach 1:
The battery system is divided into multiple independent energy supply branches, each with its own series-connected battery cells. This segmentation allows individual branches to be isolated in case of failure, preventing single-point failures from affecting the entire system. The coupling units enable independent control and disconnection of each branch, implementing the segmentation principle to improve reliability while maintaining power capacity.
Solution Approach 2:
Different branches can have different numbers of series-connected cells tailored to specific power and energy requirements. This local quality approach allows optimization of each branch for particular functions while maintaining overall system reliability through redundancy. Critical functions can be assigned to branches with appropriate cell configurations.
2Power
If battery cells are heated to reduce internal resistance at low temperatures, then the power delivery capability is improved, but the energy consumption and time requirement increase
Solution Approach 1:
Instead of heating all battery cells uniformly, the system selectively activates only the necessary number of branches based on current power requirements and temperature conditions. This partial action approach reduces unnecessary heating energy consumption while ensuring sufficient power delivery capability by using only the required subset of available branches.
Solution Approach 2:
The system dynamically adjusts the number of active branches based on real-time temperature conditions and power demands. At low temperatures, more branches can be activated to provide sufficient power. As temperatures rise or power demands decrease, fewer branches are needed, reducing energy consumption. This dynamic adaptation optimizes the balance between power delivery and energy efficiency.
3Power
If more battery modules are connected in series to increase power capacity, then the power output is improved, but the risk of system failure increases due to more potential failure points
Solution Approach 1:
Rather than using a single long series string of cells, the system segments the battery into multiple parallel branches with fewer series cells each. This achieves the same total power capacity through parallel current paths while reducing the number of series connection points where failures can occur. Each branch operates independently, so failures in one branch do not propagate to others.
4Device complexity
If conventional battery cells are used at low temperatures, then the system simplicity is maintained, but the power output is reduced due to high internal resistance
Solution Approach 1:
The system uses identical conventional battery cell designs across all branches, maintaining manufacturing simplicity and system uniformity. However, it achieves multi-functionality by enabling these same cells to operate effectively across a wide temperature range through the parallel branch architecture. At low temperatures, more branches are activated to compensate for increased internal resistance, while at high temperatures, fewer branches are needed.
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
Reduces energy and time requirements for heating, enabling quicker vehicle startups and efficient power supply by selectively using low-resistance cells at low temperatures, with all cells warming up for full capacity during operation.
Implementation Method 1
Customary batteries, such as lithium-ion batteries, for example, have a temperature-dependent internal resistance. At low temperatures, the internal resistance is increased
Data Source
AI summary
The invention relates to an energy storage device for generating an n-phase supply voltage for an electrical machine, where n≧1, or for an inverter, with n energy supply branches connected in parallel, each of which can be connected to one of n phase lines, each of the energy supply branches comprising a plurality of series-connected energy storage modules, each comprising: an energy storage cell module and a coupling device configured to selectively connect the energy storage cell module into the respective energy supply branch or to bypass said module, the energy storage cell modules of respective first energy storage modules of an energy supply branch each comprising at least one first energy storage cell, the energy storage cell modules of respective second energy storage modules of an energy supply branch each comprising at least one second energy storage cell, and the first energy storage cells having a lower internal resistance than the second energy storage cells below a predetermined temperature threshold.