Battery Pack Current Path Forming Unit for Lithium Safety
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Solution Overview
Problem
Lithium batteries face damage due to uncontrolled charging currents, as existing rectifiers designed for lead-acid batteries cannot accurately limit currents, leading to potential damage from high internal resistance.
Innovation Solution
A battery pack system with a current path forming unit, comprising FETs and a current limiting module, controlled by a BMS to form different charging and discharge current paths based on voltage and current comparisons, ensuring safe charging and discharging currents for lithium batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an existing rectifier designed for lead-acid batteries is used with lithium batteries, then the rectifier can be universally applied to different battery types, but the charging current cannot be accurately limited causing battery damage
Solution Approach 1:
A current path forming unit is introduced as an intermediary component between the rectifier and the lithium battery. This unit includes switching elements (MOSFETs or IGBTs) and a current limiting module that actively control the charging current path, preventing excessive current from reaching the battery while allowing the existing rectifier to remain in use
Solution Approach 2:
The charging system is segmented into distinct functional modules: the rectifier module for voltage conversion, the current path forming unit with switching elements for path control, and the current limiting module for current regulation. This segmentation allows each module to perform its specific function optimally while working together as an integrated system
2Reliability
If a current limiting module is added to form different current paths for charging and discharging, then battery safety is improved through accurate current control, but device complexity increases
Solution Approach 1:
The current path forming unit is designed to perform multiple functions: it forms different current paths for charging and discharging operations, provides current limiting protection, and enables the system to work with both lead-acid and lithium batteries. The switching elements can operate in different configurations to achieve various control objectives
Solution Approach 2:
The current path forming unit combines the functions of path selection and current limiting into a single integrated circuit block. The switching elements and current limiting module are merged to work together, reducing the need for separate control circuits and simplifying the overall system architecture
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
The system effectively limits charging currents and selects appropriate discharge paths, preventing damage to lithium batteries by ensuring currents do not exceed safe limits, allowing the use of existing rectifiers with lithium batteries.
Implementation Method 1
the existing lead-acid battery has large resistance of the battery itself, and thus the battery is not damaged, even when a charging current is not separately limited by the rectifier. However, for a lithium battery, since the internal resistance is very small, the battery may be damaged when a charging current is not accurately limited.
Implementation Method 2
The current path forming unit may include a first FET; a second FET; and a current limiting module, wherein the first FET and the second FET are connected in series
Data Source
AI summary
A battery pack according to an embodiment of the present disclosure is connected to a rectifier, and is composed of a (+) terminal formed by connecting a plurality of (+) terminals of a plurality of battery modules, a (+) output terminal connected to a (+) input terminal of the rectifier, a BMS configured to control charging or discharging of the battery pack, and a current path forming unit disposed between the (+) terminal and the (+) output terminal and configured to form a current path between the (+) terminal and the (+) output terminal according to the control by the BMS.