Series Battery Switch Voltage Distribution via Segmentation
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Solution Overview
Problem
Conventional battery management systems for series-connected batteries require high-voltage-rated controllable switches, which increase costs and internal series resistance, limiting the number of batteries due to high costs and efficiency losses, and result in prohibitively expensive solutions.
Innovation Solution
The system employs a plurality of controllable switches to disconnect batteries simultaneously from an external circuit, distributing voltage among switches, allowing for reduced voltage ratings and costs, with balancing resistors ensuring even voltage distribution across series-connected battery/switch pairs for predictable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage-rated controllable switches are used to disconnect series-connected batteries, then the switch can tolerate the maximum voltage, but the cost and internal series resistance increase
Solution Approach 1:
The patent divides the high-voltage switching function into multiple lower-voltage switches connected in series, where each switch handles a portion of the total battery voltage. This segmentation allows using multiple low-voltage-rated switches instead of a single high-voltage-rated switch, reducing cost and internal resistance while maintaining the required voltage tolerance capability
Solution Approach 2:
The patent combines multiple low-voltage switches in series to achieve the equivalent function of a single high-voltage switch. By merging these switches into a series configuration, the system attains the necessary voltage tolerance through collective action of individual switches, each operating within its lower voltage rating
2Reliability
If high-voltage-rated controllable switches are used to disconnect series-connected batteries, then the switch can tolerate the maximum voltage, but the internal series resistance increases causing efficiency losses
Solution Approach 1:
By segmenting the voltage handling across multiple low-voltage switches, each switch has lower internal resistance compared to a single high-voltage switch. The cumulative effect of multiple low-resistance switches in series results in lower total resistance, reducing I²R losses and improving overall system efficiency
Solution Approach 2:
The patent changes the voltage rating parameter of the switches from high to low, and compensates by changing the number of switches from one to multiple. This parameter transformation allows selecting switches with optimized resistance characteristics for lower voltage operation, thereby reducing energy losses
3Reliability
If high-voltage-rated controllable switches are used to disconnect series-connected batteries, then the system can handle high voltage, but the number of batteries is limited due to high costs
Solution Approach 1:
The segmentation approach enables scalable system design where additional battery modules can be incorporated by adding corresponding low-voltage switches in series. This modular architecture removes the cost barrier that would otherwise limit the number of batteries, allowing flexible expansion of battery capacity
4Ease of manufacture
If multiple controllable switches are used to distribute voltage, then the voltage rating and cost are reduced, but the voltage distribution among switches must be even for predictable operation
Solution Approach 1:
The patent introduces balancing resistors as intermediary elements connected in parallel with each switch-battery pair. These resistors act as mediators that equalize the voltage distribution across switches by providing alternative current paths, ensuring predictable operation even with variations in switch characteristics
Data Source
AI summary
Systems and methods of providing integrated battery protection for a plurality of series-connected batteries, in which a plurality of controllable switches are used to disconnect or otherwise isolate the respective batteries, substantially simultaneously, from an external circuit in response to certain fault or non-fault battery conditions. When the plurality of controllable switches are synchronously transitioned from a closed or “ON” state to an opened or “OFF” state, the voltages of the respective batteries become distributed among the controllable switches, allowing for the use of switches having a reduced voltage rating as well as a reduced cost. By connecting a balancing resistor across each of a plurality of series-connected battery/switch pairs, a more even distribution of the voltages of the respective batteries among the controllable switches can be achieved, providing the system with more predictable operation.