Battery Control Device Voltage Offset for Cell Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control methods for secondary batteries in hybrid and electric vehicles fail to effectively prevent deterioration due to overcharge or overdischarge, leading to voltage variations among battery cells that can result in reduced battery performance and lifespan.
Innovation Solution
A control device with an abnormality sensing unit, voltage sensing unit, offset addition unit, and charge/discharge control unit that adjusts voltage values by adding an offset amount to each battery block, limiting charge and discharge power based on sensed voltage values, thereby preventing overcharge and overdischarge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cell group is charged such that the average unit cell voltage exceeds the upper limit voltage by a predetermined voltage, then the charge power is maximized, but the battery characteristics deteriorate due to overcharge
Solution Approach 1:
The patent calculates a voltage offset amount before charging based on the difference between the upper limit voltage and the average unit cell voltage. This preliminary calculation allows the control device to set appropriate charge power limits in advance, preventing overcharge while maximizing charge efficiency. The offset amount is computed as: offset = (upper limit voltage - average unit cell voltage) × number of cells, ensuring that charging stops before any cell exceeds its voltage limit.
Solution Approach 2:
The patent dynamically adjusts the charge power parameter based on the calculated voltage offset. By changing the charge power parameter according to the offset amount, the system optimizes charging efficiency while preventing overcharge. The charge power is limited to: charge power ≤ (upper limit voltage - offset) × charge current, which adapts to the real-time state of battery cells.
2Measurement precision
If voltage sensing is performed on each individual battery cell, then overcharge/overdischarge can be precisely detected, but the device complexity increases
Solution Approach 1:
The patent extracts the voltage sensing function from the individual cell level to the battery block level. Instead of installing voltage sensors on each cell, the system measures the total voltage of each battery block (which contains multiple cells in series) and calculates the average unit cell voltage by dividing the block voltage by the number of cells. This extraction principle reduces the number of sensors required while maintaining sufficient monitoring capability.
Solution Approach 2:
The patent creates a virtual representation of individual cell voltages through calculation rather than direct measurement. By computing the average unit cell voltage from block voltage measurements and using this calculated value to determine charge/discharge limits, the system achieves indirect monitoring of cell-level conditions without the complexity of direct cell-level sensing.
3Reliability
If the charge power is limited based on the upper limit voltage, then overcharge is prevented, but the charging efficiency decreases
Solution Approach 1:
The patent implements dynamic charge power adjustment based on real-time battery state. The charge power limit is not fixed but is continuously updated according to the calculated voltage offset, which changes as battery cells charge and discharge. This dynamic adjustment allows the system to maintain high charging efficiency when cells are far from the voltage limit while preventing overcharge as cells approach the limit, optimizing the trade-off between charging speed and safety.
Data Source
AI summary
A control device for a secondary battery includes an offset addition unit calculating an offset amount based on a plurality of voltage values sensed by a sensor, the number of a plurality of battery cells included in one battery block and a preset range, and adding an offset amount to the sensed voltage values, when a flag is turned on to indicate the fact the voltage value of one of the battery cells falls within a preset range, and also includes an I/O control unit controlling charge/discharge of the battery based on voltage values containing the offset amount added thereto. Even when the battery voltage is sensed a battery block at a time, the voltage value can be controlled a cell at a time.