Variable Reference Voltage for Battery Overvoltage Detection
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Solution Overview
Problem
Conventional electric storage devices with serially connected storage elements face reliability issues due to variations in internal resistance and voltage concentration during charging, especially at low temperatures, leading to prolonged charging times and potential deterioration of storage elements.
Innovation Solution
The electric storage device incorporates a charging/discharging limiting circuit with a variable reference voltage source that adjusts based on detected charging current and temperature, ensuring smooth charging and reliable overvoltage detection to prevent element deterioration, by using a control unit to dynamically adjust the reference voltage and limit charging current when peak voltages are reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a fixed reference voltage is used for overvoltage detection during charging, then the detection threshold is stable and simple to implement, but charging time is prolonged due to premature charging current limitation caused by internal resistance variations and voltage concentration
Solution Approach 1:
The reference voltage source is changed from a fixed value to a variable value that dynamically adjusts based on the charging current. During constant current charging, the reference voltage increases with charging current to account for voltage concentration effects, allowing charging to proceed without premature limitation. This dynamic adjustment resolves the contradiction by adapting the detection threshold to actual operating conditions.
Solution Approach 2:
The reference voltage parameter is changed from a constant value to a variable value that depends on charging current magnitude. This parameter change allows the overvoltage detection threshold to compensate for internal resistance variations and voltage concentration during charging, thereby reducing charging time while maintaining detection accuracy.
2Productivity
If the charging current is increased to improve charging efficiency, then charging speed increases, but voltage concentration on storage elements with high internal resistance becomes more significant, causing premature charging limitation
Solution Approach 1:
The reference voltage dynamically increases with charging current during constant current charging, creating a moving threshold that accommodates higher charging currents. This allows the system to maintain high charging efficiency without premature limitation, as the detection threshold adapts to the increased voltage concentration effects at higher currents.
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 effectively mitigates the impact of internal resistance variations and voltage concentration, enabling efficient charging and reliable overvoltage detection, thereby extending the life of storage elements and improving charging efficiency, especially in low-temperature conditions.
Implementation Method 1
Voltage detection unit 22 is provided so as to detect a voltage between plus-side terminal 24P of storage element 24C and minus-side terminal 30M of storage element 30C
Implementation Method 2
a lower-limit voltage and an upper-limit voltage, which are allowed during discharging and charging, are set in reference voltage sources 32 and 34 and compared in voltage comparison units 36 and 38 with a detection voltage detected by voltage detection unit 22
Implementation Method 3
charging/discharging limiting switch control unit 40, and charging/discharging limiting switch 42... when the detection voltage exceeds reference voltage source 34, charging to the storage element is limited through charging/discharging limiting switch 42
Data Source
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AI summary
Electric storage device (100) is provided which is capable of smoothly charging storage elements (102C, 104C, 106C) and reliably detecting an overvoltage of each of the storage elements. Electric storage device (100) includes charging/discharging limiting circuit (101). Charging/discharging limiting circuit (101) includes charge element (112), discharge element (114), control unit (118), charging current detection unit (120), voltage detection unit (122), valuable reference voltage source (124), and voltage comparison unit (126). A magnitude of valuable reference voltage source (124) that is connected to an input terminal on a first side of voltage comparison unit (126) is adjusted by charging current detection unit (120). Detection signal (122B) from the voltage detection unit is given to an input terminal on a second side of voltage comparison unit (126).