Battery Monitor Stack Current Equalization via Equipotential VSS
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Solution Overview
Problem
Conventional battery stack systems face inefficiencies due to unbalanced cell loads, electromagnetic interference (EMI), hot swap, and electrostatic discharge (ESD) effects, which reduce their lifespan and accuracy in hybrid electric vehicles (HEV) and electric vehicles (EV).
Innovation Solution
A battery stack monitoring system with integrated circuits that regulate voltage and current, using high impedance inputs and voltage reference circuits to form a single current loop, reducing EMI susceptibility and protecting against ESD and hot swap through high-value resistors, thereby maintaining balanced cell loads and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional battery monitors are used to measure cell characteristics, then monitoring capability is provided, but unbalanced current drain occurs across battery cells
Solution Approach 1:
The patent connects the VSS pins of all battery monitors together to form a common reference potential, ensuring that all monitors operate from the same voltage reference. This equipotential connection prevents unbalanced current drain by eliminating potential differences between monitor ground references, thereby resolving the contradiction between maintaining monitoring precision and achieving current balance.
2Measurement precision
If battery monitors are connected in a conventional stacked configuration, then voltage and current measurement is enabled, but susceptibility to EMI increases
Solution Approach 1:
The patent merges the VSS connections of all battery monitors into a single common node, creating a unified reference ground for the entire stack. This merging approach reduces EMI susceptibility by minimizing the loop areas and antenna effects that would otherwise exist between separate ground connections, while still enabling accurate voltage and current measurements across all cells.
3Ease of operation
If conventional battery monitor connections are used, then system operation is maintained, but protection against ESD and hot swap is insufficient
Solution Approach 1:
The patent implements protective measures beforehand by connecting high-value resistors between the VSS pins of adjacent battery monitors. These resistors are pre-installed to cushion against ESD and hot swap events before they occur, allowing the system to maintain normal operation while being protected against electrical transients and improper connection events.
4Productivity
If frequent cell balancing is performed to maintain battery efficiency, then cell balance is improved, but power demands increase
Solution Approach 1:
The patent employs battery monitors with feedback capability to continuously measure cell voltages and detect imbalances. By providing real-time feedback on cell states, the system can identify when balancing is needed and when it is not, allowing for efficient operation without unnecessary balancing cycles that would consume additional power.
Data Source
AI summary
Embodiments of the present invention may provide a battery monitor for a battery system that avoids current loops. A battery monitor may be provisioned as an integrated circuit and may include a pair of supply pins for reception of power to the integrated circuit, a third high impedance pin, and a voltage regulation circuit. When the circuits are deployed, the supply pins of several battery monitors may be connected to each other to form a stack. The high impedance inputs of each battery monitor may be coupled to low voltage terminals of an associated battery cell. A voltage reference circuit within the battery monitor may maintain the voltage at a low voltage supply of the monitors at a level that matches the voltage present on the high impedance input. Thus, the voltages on the monitors' low voltage supplies may be regulated. As a result, no current should flow through the high impedance pins of the battery monitor. All current flow should occur through a single loop that extends through the entire stack of battery monitors.