Battery Internal Resistance Estimation via Partial Discharge
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Solution Overview
Problem
Diagnosing the sub-battery in a vehicle is challenging due to the difficulty in measuring its internal resistance, especially when the main battery fails, as the sub-battery may not have the opportunity to discharge during normal travel and may not have sufficient power to perform a discharge for diagnosis.
Innovation Solution
A diagnostic device and method that estimate the internal resistance of the battery by discharging at two current values smaller than the target current value for shorter periods, allowing for the calculation of the internal resistance when discharging at the target current value, thereby enabling battery diagnosis while minimizing discharge current and period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sub-battery is discharged at target current during target period for diagnosis, then the internal resistance measurement accuracy is improved, but the power consumption increases and the battery may not have sufficient power to complete the discharge
Solution Approach 1:
The patent applies partial action by performing discharge at current values smaller than the target current and for periods shorter than the target period. Multiple partial discharge tests are conducted and their results are synthesized to estimate the internal resistance, avoiding the need for a single full target discharge that would consume excessive power.
Solution Approach 2:
The patent performs preliminary discharge tests at smaller current values before attempting target current discharge. These preliminary tests provide initial internal resistance measurements that help determine whether the battery has sufficient power for target current discharge, and the results are used to estimate the target internal resistance without requiring actual target current discharge.
2Measurement precision
If the sub-battery is discharged during normal traveling for diagnosis, then the internal resistance can be measured, but the main battery failure scenario cannot be properly tested
Solution Approach 1:
The patent changes the discharge parameters (current values and periods) from the target current and target period used in failure scenarios to smaller current values and shorter periods suitable for normal traveling conditions. By measuring internal resistance at multiple parameter combinations and synthesizing the results, the method achieves reliable diagnosis under normal conditions without requiring actual failure scenario testing.
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
Enables accurate estimation and diagnosis of the battery's internal resistance, ensuring it can supply a predetermined power, even for sub-batteries that are difficult to discharge, by reducing the influence on the calculated internal resistance value through controlled discharge patterns.
Implementation Method 1
causing the battery to perform discharge at a first current value smaller than a predetermined target current value during a first period shorter than a predetermined target period
Data Source
AI summary
A diagnostic device for a battery includes a measurement unit configured to acquire a current value and a voltage value of the battery, and a diagnostic unit configured to calculate an internal resistance value of the battery based on the current value and the voltage value acquired by the measurement unit, and diagnose the battery based on the internal resistance value. The diagnostic unit is configured to cause the battery to perform discharge at a first current value and a second current value smaller than a predetermined target current value during a first period and a second period shorter than a predetermined target period, respectively, estimate the internal resistance value when the battery is caused to perform the discharge at the target current value during the target period, and diagnose the battery.