Battery Pack Charging Circuit for High-Current Fast Charging
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Solution Overview
Problem
Cordless electrical devices have limited run-time due to battery pack capacity, and existing charging circuitry cannot handle high charging currents without adverse effects such as excessive heating or damage, limiting fast charging of battery packs with higher capacity cells.
Innovation Solution
A battery pack with a charging circuit that includes a N-Channel FET and a fuse rated for higher currents, allowing charging currents up to 20 Amperes, and an electronic controller to manage the charging process, enabling faster charging without component damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If charging current is increased to decrease charging time, then charging speed is improved, but components (PCB, fuse, FET) suffer excessive heating and damage
Solution Approach 1:
The charging circuit is divided into multiple parallel paths with individual current control. The charging current is segmented into separate channels, each handled by dedicated FETs and current regulation circuitry. This allows the total charging current to be distributed across multiple components, preventing any single component from overheating while maintaining high overall charging speed.
Solution Approach 2:
The patent implements dynamic parameter changes by using microcontroller-based control to adjust FET gate voltages and regulate charging current in real-time. The system monitors temperature and current parameters, automatically adjusting operating conditions to prevent component damage while optimizing charging speed. This includes adaptive current limiting and thermal management strategies.
2Duration of action of moving object
If battery pack capacity is increased to extend run-time, then duration of action is improved, but charging time increases proportionally
Solution Approach 1:
The high-capacity battery pack is divided into multiple parallel string configurations (e.g., 5S2P, 5S3P), where each string can be charged through dedicated circuit paths. This segmentation allows parallel charging operations, where multiple charging channels operate simultaneously to charge different portions of the battery pack, reducing overall charging time while maintaining high capacity for extended run-time.
Solution Approach 2:
The patent implements continuous charging operation by eliminating idle time in the charging process. The multi-path charging circuitry ensures that all battery cells are charged simultaneously and continuously without interruption. The system maintains optimal charging current throughout the entire charging cycle, avoiding the traditional charge-discharge cycles or idle periods, thereby reducing total charging time for high-capacity packs.
3Reliability
If charging current is limited to protect components, then component reliability is maintained, but charging speed decreases
Solution Approach 1:
The charging circuit components are designed with multi-functionality to handle both high current and protection functions. The FETs are selected with high current ratings and integrated temperature sensing capabilities. The microcontroller serves multiple functions including current regulation, temperature monitoring, and protection logic implementation. This universal design allows the same components to operate at high currents for fast charging while simultaneously providing protection functions.
Solution Approach 2:
The patent implements comprehensive feedback control systems where temperature sensors, current sensors, and voltage sensors continuously monitor component conditions and feed this information back to the microcontroller. The microcontroller adjusts charging parameters in real-time based on this feedback, allowing the system to operate at maximum safe current levels. This closed-loop control enables high charging speeds while automatically preventing component damage through real-time monitoring and adjustment.
Data Source
AI summary
One embodiment provides a battery pack including a housing, a plurality of battery cells supported by the housing, and a terminal block. The terminal block is configured to be coupled to a power tool to provide operating power from the plurality of battery cells to the power tool. The terminal block has a positive power terminal, a charging terminal, and a ground terminal. The battery pack also includes a charging circuit provided between the charging terminal and the plurality of battery cells. The charging circuit is configured to receive and transfer charging current above 12 Amperes to the plurality of battery cells during charging. The charging circuit includes a charging switch and a fuse coupled between the charging terminal and the charging switch.