Battery Charge Voltage Step-Down for Overcharge Swelling Control
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Solution Overview
Problem
Rechargeable batteries, such as lithium-ion batteries, face the issue of swelling due to overcharge conditions when kept on a charger for too long, leading to potential fires, damage, and safety hazards, as current charger and fuel gauge technologies fail to prevent continuous charging from causing heat and gas buildup.
Innovation Solution
A microcontroller unit (MCU) in the battery system uses a bit array to monitor the battery voltage against a predefined threshold, shifting bits to create a sliding window, and when a certain ratio of bits indicates prolonged charging, it steps down the charger voltage to prevent overcharging, thereby reducing the risk of swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charger and fuel gauge ICs terminate charge current when battery is full, then charging efficiency is improved, but battery swelling occurs due to continuous trickle charge
Solution Approach 1:
The system continuously monitors battery voltage and compares it against a threshold voltage to detect when the battery reaches full charge. This feedback mechanism triggers the MCU to stop the trickle charge current, preventing battery swelling while maintaining efficient charging.
Solution Approach 2:
The battery management system uses its own monitoring capabilities to automatically detect full charge conditions and terminate trickle charging without external intervention. The system serves itself by using internal voltage sensing and comparison to make charging decisions.
2Reliability
If battery is monitored continuously to prevent overcharge, then battery safety is improved, but memory requirements and device complexity increase
Solution Approach 1:
The monitoring period is divided into discrete sampling intervals, with voltage measurements taken at specific times rather than continuous monitoring. This segmentation allows safe battery monitoring using minimal memory to store only the necessary sampling data points.
Solution Approach 2:
Instead of continuous monitoring, the system performs partial monitoring at strategically chosen sampling intervals. This partial action is sufficient to detect overcharge conditions while dramatically reducing memory requirements and system complexity.
3Measurement precision
If sampling rate is increased to improve monitoring precision, then detection accuracy is improved, but memory requirements and processing load increase
Solution Approach 1:
The monitoring function is segmented into discrete sampling events rather than continuous measurement. Each sampling event captures voltage at a specific moment, providing sufficient detection accuracy while using minimal memory to store and process individual samples.
Solution Approach 2:
The system uses temporary, single-use voltage samples that are processed immediately and discarded, rather than storing continuous data streams. Each voltage sample serves its purpose for detection and is then replaced, minimizing memory requirements while maintaining detection precision.
Data Source
AI summary
An indexed sequence of bits in a buffer is allocated for tracking a battery charging state. The indexed sequence of bits has a first number of bits. A battery voltage of a rechargeable battery is sampled at a sampling rate. For each sampled battery voltage, the battery voltage is compared with a voltage threshold. A next bit position in the indexed sequence of bits is identified. In accordance with a determination that a comparison result is true, a predefined first value is added to the next bit position. A second number of bits that are filled with the predefined first value is determined. A ratio between the second number and the first number is also determined. In accordance with a determination that the ratio exceeds a threshold step-down ratio, a battery charge voltage is stepped down. The rechargeable battery is charged to a step-down voltage.