Cell-Level Battery Charging Control Under Undervoltage Protection
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Solution Overview
Problem
Lithium iron phosphate batteries face issues with under and over voltage protection modes that prevent charging and cause electrical system malfunctions, and conventional charging systems can damage cells with high voltage and current, as well as improper charging due to ripple.
Innovation Solution
A battery management system that controls charge and charging of each cell individually, includes under and over voltage protection modes, regulates voltage and current, and emulates standard battery impedance to maintain system stability, with features like cell balancing, communication, and smart charger detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If under voltage protection mode disconnects the cell pack from battery posts to prevent complete discharge, then battery safety is improved, but automatic battery chargers cannot detect the condition and charging is prevented
Solution Approach 1:
A virtual battery is introduced as an intermediary between the cell pack and the charging system. The virtual battery maintains electrical connection and voltage signal presence even when the cell pack is disconnected for protection, allowing chargers to detect and communicate with the system while preventing harmful charging currents from reaching the protected cells
Solution Approach 2:
The virtual battery creates a copy or simulation of the battery's electrical characteristics (voltage, impedance) that mimics a normal battery state. This copy allows the charging system to operate normally in terms of detection and control signals, while the actual cell pack remains protected through physical disconnection
2Productivity
If charging system generates high voltage and high current to charge battery quickly, then charging speed is improved, but cells can be damaged
Solution Approach 1:
The system dynamically adjusts charging parameters based on real-time cell conditions. The virtual battery enables continuous monitoring and adaptive control of voltage and current, allowing the system to optimize charging speed while preventing damage by reducing current when cells approach voltage limits or show signs of stress
Solution Approach 2:
The virtual battery provides continuous feedback about the actual battery state to the charging control system. This feedback loop enables the charger to adjust its output in real-time, preventing over-voltage and over-current conditions that could damage cells while maintaining efficient charging when conditions are safe
3Productivity
If charging system creates high ripple in direct current to increase charging power, then charging capability is improved, but improper charging occurs leading to shortened battery lifetime
Solution Approach 1:
The virtual battery enables precise monitoring of charging current quality and ripple content. The system uses this feedback to detect excessive ripple conditions and adjust charging parameters or activate filtering to protect the cells from harmful current variations that would reduce battery lifetime
Solution Approach 2:
The system changes charging parameters dynamically based on detected ripple levels. When high ripple is detected, the system modifies voltage and current parameters, activates filtering circuits, or adjusts charging phases to eliminate harmful ripple effects while maintaining effective charging capability
Data Source
AI summary
A battery management system for batteries, such as, but not limited to, electric vehicle battery packs and cells, lithium iron phosphate batteries, lead acid batteries, gel batteries, and absorbed gel mat batteries, in engine start applications is disclosed. The battery management system is configured to control the charge and charging of each cell individually. The battery management system may be configured to control the charge of a battery which may consist of a plurality of cells, such as, but not limited to, lithium iron phosphate cells, and in at least one embodiment, the battery may consist of, but is not limited to being formed from, four lithium iron phosphate cells connected in series and a battery management system to ensure proper charge and safe operation.