Secondary Battery Charging Threshold Control for Overcharge Margin
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Solution Overview
Problem
Existing secondary battery charger systems face challenges in preventing excessive restriction of charging amount while avoiding overcharging, particularly due to delayed response in current control, leading to temporary voltage exceeding the target voltage and potential battery deterioration.
Innovation Solution
A secondary battery charger system that calculates chargeable power based on the difference between the charging target voltage and cell voltage, with a charging threshold voltage setting unit that sets the target voltage lower than the charging limitation voltage, and a charging control unit that stops charging if the cell voltage exceeds the target but is below the limitation voltage, using a timer to measure the dwelling time within an allowable voltage zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charging current is restricted to zero when the cell voltage exceeds the charging target voltage, then the charging voltage is prevented from significantly exceeding the target voltage, but the charging amount is excessively restricted even when the secondary battery does not reach an overcharging state
Solution Approach 1:
The patent changes the parameter from a binary charging stop condition to a time-based conditional stop. Instead of immediately stopping charging when voltage exceeds the target, the system allows charging to continue for a predetermined time period after exceeding the target voltage, provided the voltage remains below the limitation voltage. This temporal parameter adjustment resolves the contradiction by balancing safety (preventing overcharging) with productivity (maintaining sufficient charging amount).
Solution Approach 2:
The patent introduces dynamic control by implementing a time-dependent charging stop condition. The charging control unit dynamically evaluates whether to stop charging based on how long the voltage has exceeded the target and whether it remains within the limitation voltage. This dynamic approach allows the system to adapt to temporary voltage excursions caused by response delays while still preventing dangerous overcharging conditions.
2Reliability
If the charging current is reduced when the voltage exceeds a certain threshold, then the voltage is controlled, but the charging process is stopped when the voltage repeatedly exceeds a protection voltage, reducing charging efficiency
Solution Approach 1:
The patent changes the protection mechanism from immediate stoppage upon threshold exceedance to a time-based evaluation. The system monitors the duration and frequency of voltage excursions above the target voltage and only stops charging after a predetermined time period if the voltage remains within safe limits. This parameter change maintains voltage control while improving charging efficiency by avoiding premature stoppages.
3Reliability
If a charging threshold voltage is set lower than the charging limitation voltage to account for response delay, then overcharging is prevented, but the charging amount is unnecessarily restricted
Solution Approach 1:
The patent implements dynamic voltage threshold evaluation combined with time-based control. Instead of using a fixed lower threshold that permanently restricts charging, the system allows charging to continue dynamically evaluating whether the voltage exceeds the target for a predetermined time period. This dynamic approach prevents overcharging while maximizing the charging amount by allowing additional charging capacity that would otherwise be unnecessarily restricted.
Solution Approach 2:
The patent takes preliminary action by setting the charging target voltage lower than the limitation voltage to account for potential response delays, but then compensates by allowing continued charging for a predetermined time period after exceeding the target. This preliminary protective measure is balanced by a compensatory mechanism that restores charging capacity, thereby preventing overcharging while minimizing restriction on charging amount.
Data Source
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AI summary
A secondary battery charger system in which a chargeable power capacity is calculated on the basis of a difference between a charging target voltage and a cell voltage using a charging control unit that controls a charger used to charge a secondary battery, the secondary battery charger system including a charging threshold voltage setting unit configured to set the charging target voltage to be lower than a charging limitation voltage which is an upper limitation of the cell voltage allowable in design. The charging control unit stops the charging if a predetermined charging stop condition is satisfied while the cell voltage exceeds the charging target voltage and is lower than the charging limitation voltage.