EV Battery Pack Switching Strategy for Weight Reduction
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Solution Overview
Problem
High-power relays used in electric vehicle battery packs are bulky, expensive, and affect reliability due to their high breaking power requirements, contributing to increased weight and cost.
Innovation Solution
A battery pack system that uses a single high-capability circuit breaker for current interruption and arc extinction at one pole, with other poles isolated by lower-capability switches, and a control module to manage sequential connections and disconnections, ensuring no current flows through the secondary switches during transitions to prevent arcs and allow for reduced switching capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-power relays with full breaking capability are used in all poles of the battery pack, then the system can reliably interrupt current and extinguish electric arcs, but the weight, size, and cost of the battery pack increase significantly
Solution Approach 1:
The patent divides the battery pack poles into two groups: a first group of poles (including the positive pole) equipped with high-power relays having full breaking capability, and a second group of poles (including the negative pole) equipped with lower-power relays having reduced breaking capability. This segmentation allows the system to maintain necessary reliability where full breaking capability is required while reducing overall weight and cost by using smaller relays in positions where full breaking capability is not needed.
Solution Approach 2:
The patent applies different relay specifications to different poles based on their specific requirements. The first poles receive relays with full breaking capability to handle arc extinction and high-current interruption, while the second poles receive relays with reduced breaking capability since they primarily need to handle nominal current circulation. This local differentiation optimizes the balance between reliability and weight.
2Reliability
If high-power relays with full breaking capability are used in all poles of the battery pack, then the system can reliably interrupt current and extinguish electric arcs, but the cost of the battery pack increases
Solution Approach 1:
The patent segments the relay configuration into two categories: high-power relays for the first group of poles and lower-power relays for the second group of poles. This segmentation reduces the overall cost by eliminating the need to purchase and install expensive high-power relays in all positions, while still maintaining the necessary breaking capability in critical positions.
Solution Approach 2:
The patent implements local quality by assigning different relay types to different poles based on their functional requirements. Only the first poles (particularly the positive pole) receive the expensive high-power relays with full breaking capability, while the second poles receive more economical lower-power relays, thereby reducing the total manufacturing cost while preserving reliability where needed.
3Reliability
If multiple high-power relays are used in the battery pack, then the breaking capability and arc extinction ability are sufficient, but the battery pack size increases
Solution Approach 1:
The patent segments the relay population into high-power relays for the first group of poles and compact lower-power relays for the second group of poles. This segmentation reduces the total space required in the battery pack by using smaller relays in positions where full breaking capability and arc extinction capability are not both required, thereby reducing the overall battery pack footprint.
Solution Approach 2:
The patent applies local quality by providing full arc extinction capability only in the first group of poles (particularly the positive pole) where it is most critical, while the second group of poles uses smaller relays that do not require full arc extinction capability. This localized approach to arc extinction reduces the total space occupied by relay components in the battery pack.
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 the weight, size, and cost of the battery pack by using smaller, cheaper switches while maintaining reliability through controlled current management, eliminating arcs during transitions.
Implementation Method 1
capability of interrupting an electric current and extinguishing an electric arc generated upon such electric current interruption
Implementation Method 2
electromechanical switches are connected to both positive and negative poles of the battery, and are dimensioned to open or close high-current paths
Data Source
Figure 1~2
Figure 3
AI summary
The present invention refers to an electric power supply system, comprising a power source (1) having first and second poles (2,3), a circuit breaker device (4) connected at the first pole (2) and a switch device (5) connected at the second pole (3). A control module (7) is adapted for sequentially opening and closing the circuit breaker and the switch device (4,5), such that the control module (7) would open or close the switch device (5) only when no current is flowing through the circuit breaker device (5). Since the switch device (5) would never break current flowing through the power source (1), it can be implemented as a switch of reduced size and reduced costs, such that the overall weight and cost of the system is reduced. The invention is preferably applied in the manufacture of battery packs for battery-powered vehicles.