Dynamic Charging Voltage Control for Battery Packs
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Solution Overview
Problem
Constant voltage charging methods for battery packs with serially connected cells lead to increased charging time and incomplete charging due to variations in battery cell characteristics, as the charging voltage remains constant despite differences in cell voltages.
Innovation Solution
A charging device and method that calculates a maximum charging voltage based on the total battery voltage, fully charged voltage, and the number of cells in series, adjusting the charging voltage to ensure all cells reach full charge while preventing overcharging by subtracting the variation in cell voltages from the total battery voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant voltage charging is applied to battery pack with serially connected cells, then charging voltage is maintained at set value, but charging time is increased and charging may not reach fully charged voltage
Solution Approach 1:
The patent applies dynamics by transitioning from constant voltage charging to a dynamic charging voltage that changes over time. The charging voltage is initially set higher than the standard constant voltage to accelerate charging, then gradually reduced as cells approach full charge. This dynamic adjustment resolves the contradiction by enabling both faster charging and reliable completion without overcharging.
Solution Approach 2:
The patent changes the charging voltage parameter from a fixed constant value to a time-varying parameter. The charging voltage starts at a higher level (Voc + ΔV) and decreases as charging progresses, allowing the system to achieve both rapid initial charging and precise termination when cells reach full charge, thereby reducing total charging time while ensuring complete charging.
2Productivity
If charging voltage is increased to reduce charging time, then charging speed is improved, but risk of over-charging increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring cell voltages and adjusting the charging voltage accordingly. When any cell approaches its maximum voltage, the charging voltage is automatically reduced, preventing over-charging. This feedback mechanism enables high charging speeds while maintaining safety by dynamically responding to real-time battery state.
Solution Approach 2:
The charging voltage is made dynamic rather than static, allowing it to adapt to the charging state. The voltage starts high for rapid charging but automatically decreases as cells near full charge, eliminating the need to choose between high voltage (fast charging with overcharge risk) and low voltage (safe but slow charging).
3Reliability
If cell balancing is performed to cope with voltage variations, then over-charging is prevented, but charging time is further increased
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the charging voltage before any cell reaches its maximum voltage. Instead of waiting for voltage imbalances to develop and then performing corrective balancing (which wastes time), the charging voltage is preemptively reduced when cells show signs of approaching full charge, preventing imbalances before they occur and eliminating the need for time-consuming balancing operations.
Data Source
AI summary
There is provided a charging device including a charging voltage providing unit configured to provide a maximum charging voltage for an electricity storage unit, wherein the electricity storage unit includes a plurality of battery cells, and wherein the maximum charging voltage satisfies an equation (1) below: Maximum Charging Voltage=Total Battery Voltage+(Fully Charged Voltage−Maximum Cell Voltage)*n (1) wherein n represents a total number of the battery cells connected in series.