Battery Control Unit Voltage Detection Correction
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Solution Overview
Problem
Existing battery control systems face detection accuracy issues due to varying contact and internal resistances in battery cells, leading to voltage detection errors, especially when the time constant of the low pass filter becomes larger, and the inability to account for resistance changes over time.
Innovation Solution
A battery control unit that includes a voltage detection unit, a correction value calculation unit, and a voltage calculation unit to accurately calculate the battery cell voltage by determining the voltage drop at the connection member during discharging, allowing for real-time correction and immediate voltage detection without waiting for capacitor recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the time constant of the low pass filter is increased to eliminate noise more effectively, then noise elimination capability is improved, but voltage detection accuracy deteriorates due to larger voltage drops during discharge
Solution Approach 1:
The system performs preliminary discharge of the capacitor through the discharge circuit before voltage detection. This preliminary action removes the stored charge from the capacitor, preventing it from causing voltage detection errors. By discharging the capacitor in advance, the system ensures that the voltage detected by the detection circuit accurately reflects the battery cell voltage without being influenced by capacitor discharge effects.
Solution Approach 2:
The control unit monitors the voltage detection timing and controls the discharge circuit based on detected voltage values. When the detected voltage falls below a predetermined threshold, the control unit activates the discharge circuit to recharge the capacitor, maintaining optimal operating conditions for accurate voltage detection while filtering noise.
2Measurement precision
If voltage detection is delayed until capacitor discharge influence disappears, then voltage detection accuracy is improved, but detection response time deteriorates
Solution Approach 1:
The capacitor is discharged in advance through the discharge circuit before voltage detection occurs. This preliminary discharge action ensures that the capacitor's stored charge will not interfere with the upcoming voltage measurement, allowing immediate accurate detection without waiting for natural discharge decay.
Solution Approach 2:
The discharge circuit operates periodically based on voltage detection results. When the capacitor voltage drops below a threshold, the discharge circuit is activated to recharge it, creating a periodic cycle that maintains optimal conditions for continuous accurate voltage detection without prolonged delays.
3Device complexity
If a fixed correction value determined in the design phase is used, then device complexity is reduced, but adaptability deteriorates due to inability to account for resistance changes over time
Solution Approach 1:
The system uses its own voltage detection capability to automatically determine correction values during operation. By detecting the voltage difference between the battery cell and the detection circuit, the system self-calibrates the correction value without requiring external equipment or complex pre-programmed correction tables, achieving both simplicity and adaptability.
Solution Approach 2:
The correction value is dynamically adjusted based on detected voltage differences and resistance changes over time. Instead of using a fixed design-phase correction value, the system continuously updates the correction parameter to reflect actual operating conditions, including aging-related resistance changes, thereby maintaining accuracy throughout the battery's lifecycle.
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 solution enables accurate and prompt detection of battery cell voltages, reducing errors caused by resistance changes and eliminating the need to wait for capacitor recovery, thus improving detection accuracy and efficiency.
Implementation Method 1
a filter circuit (31) provided for each of the battery cells, including a capacitor (33) and eliminating noise included in voltage transmitted from the battery cell
Implementation Method 2
a discharge circuit (34) including a discharge switch (22) provided for each of the battery cells and connected in series to the battery cell via the connection member and a discharge resistor (35)
Data Source
AI summary
A battery control unit is adapted for a power supply system provided with a storage battery series-connected battery cells, a filter circuit, a discharge circuit, and a connection member connecting between the battery cell and the filter circuit.The battery control unit includes a voltage detection unit detecting voltage at the battery cell where noise is eliminated by the filter circuit, the voltage being detected immediately before/after a discharging is performed through the discharge circuit; a correction value calculation unit that calculates an amount of a voltage drop at the connection member when a discharging is performed through the discharge circuit, to be a correction value; and a voltage calculation unit that calculates voltage of the battery cell by adding the correction value calculated by the correction value calculation unit to a post-discharge voltage detected immediately after the discharging by the voltage detection unit.