Battery Cell Balancer Circuit with Bypass Switch for Overcharge Protection
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Solution Overview
Problem
Existing energy storage systems in electric vehicles, hoists, and forklifts face challenges in protecting battery cells from overcharging, which can lead to reduced service life and environmental impact due to material consumption, and require effective management of charging currents to prevent damage.
Innovation Solution
A series connection of battery cells with a balancer circuit and controllable switch allows bypassing charging current to individual cells, comparing voltages with reference values to prevent overcharging, and using a galvanically isolated signaling channel to notify controllers of critical conditions, thereby extending battery life and reducing material consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a common charging current is supplied to a series connection of battery cells, then the charging process is simplified, but individual battery cells may become overcharged leading to reduced service life
Solution Approach 1:
The patent divides the common charging current into individual controllable current paths for each battery cell by introducing separate controllable switches (transistors) for each cell. This segmentation allows independent monitoring and control of charging current for each cell, preventing overcharging while maintaining simplified overall charging operation through centralized control logic.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the voltage of each battery cell and using this information to control the controllable switches. When a cell reaches its maximum voltage threshold, the system automatically stops charging that cell by opening the corresponding switch, preventing overcharging and extending battery service life.
2Reliability
If battery cells are protected from overcharging using individual controllable switches, then service life is extended, but device complexity increases
Solution Approach 1:
The patent makes the controllable switches serve multiple functions: they act as charging current switches during normal charging operation, and simultaneously serve as bypass switches for dissipating regenerative braking energy. This multi-functionality reduces the need for separate components and simplifies the overall device complexity while maintaining battery protection.
Solution Approach 2:
The patent combines the charging control function and the regenerative braking energy dissipation function into a single integrated system using the same controllable switches and control logic. This merging of functions reduces component count and simplifies the charging control system while achieving both battery protection and energy management.
3Reliability
If a braking resistor is used to dissipate excess energy from the intermediate circuit, then overvoltage is prevented, but material consumption and environmental impact increase
Solution Approach 1:
The patent enables the battery cells themselves to serve as the energy dissipation mechanism by allowing controlled reverse current flow into already-charged cells or by using the controllable switches to dissipate energy through the cells' internal resistance. This self-service approach eliminates the need for separate braking resistors and reduces material consumption while maintaining voltage control.
Solution Approach 2:
The patent recovers regenerative braking energy by redirecting it back into the battery cells through the controllable switches when the intermediate circuit voltage exceeds the battery voltage. This energy recovery approach discards the need for energy-dissipating braking resistors, reducing material consumption and environmental impact while maintaining reliable voltage control.
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
This solution effectively protects battery cells from overcharging, extends their service life, and improves environmental protection by minimizing material usage, while also potentially reducing the need for a braking resistor by dissipating excess energy through a short-circuited switch.
Implementation Method 1
each arrangement having a controllable switch, in particular a bypass switch, with which the charging current can be routed past the battery cell, in particular as a bypass current, a means for comparing a first voltage value corresponding to the voltage present at the battery cell with a reference voltage value being provided
Implementation Method 2
also to a galvanically isolated signaling channel via which an analog value can be transmitted
Implementation Method 3
If the voltage in the intermediate circuit exceeds a critical value, the energy can be destroyed as a short-circuit current via the bypass switch of the balancing circuit. A braking resistor can thus be saved or designed to be less powerful.
Data Source
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AI summary
A device, in particular an electric vehicle, lifting mechanism, shelf-rack serving unit with lifting mechanism or fork lift truck, with an energy accumulator, from which an inverter, which feeds an electric motor, can be supplied, wherein the energy accumulator has a series connection of accumulator cells, wherein each of these accumulator cells is assigned an arrangement for controlling the charging current for the respective accumulator cell, in particular a balance circuit, in parallel, and is electrically connected, wherein each arrangement has a controllable switch, in particular bypass switch, with which the charging current can be conducted past the accumulator cell, in particular as a bypass current, wherein a means for comparing a first voltage value, corresponding to the voltage applied to the accumulator cell, with a reference voltage value is provided, the output signal of which means is fed as an actuation signal to the controllable switch, and also to a galvanically isolated signalling channel via which an analogue value can be transmitted.