Hello, I am the representative of Deepnetwork, a one-person company specializing in electric vehicle battery charging control.

NXP’s MC33771C is a 14-channel lithium-ion battery cell controller IC that can monitor the status of each cell.

 

Cell state monitoring: These chipsets monitor the status of each cell through high-precision cell voltage and temperature measurements. They use ADC conversion to measure the difference in cell voltage, and average a maximum of 256 samples to increase accuracy.

Overcharge, overcurrent, high temperature detection: The chipset supports ISO 26262 ASIL D for cell voltage, module voltage, and temperature measurements, allowing it to detect overcharge, overcurrent, and high temperature situations. In addition, these chipsets provide OV/UV, OT/UT, OC fault verification, and support OV/UV, OT/UT monitoring in Sleep mode.

Forced down function: When overcharge, overcurrent, and high temperature situations are detected, the chipset provides various functions to solve these problems. For example, it can maintain cell voltage balance through a programmable balancing timer for each MOSFET. Also, the built-in 300mA low Rdson passive cell balancing MOSFET provides diagnostic functions to monitor and adjust the cell status as needed.

 

NXP’s MC33771C chipset detects overcharge, overcurrent, and high temperature situations in the following ways:

Overcharge detection: The chipset monitors the voltage of each cell through high-precision cell voltage measurement. If the cell voltage exceeds a certain threshold, the chipset considers this an overcharge state and starts balancing for that cell.

Overcurrent detection: It can measure current with an accuracy of ±0.5% from milliamperes to kiloamperes through a current sensor and programmable gain amplifier (PGA). This allows it to detect overcurrent situations.

High temperature detection: The chipset monitors the temperature of the battery through a built-in temperature sensor. If the temperature exceeds a certain threshold, the chipset considers this a high temperature state.

These detection mechanisms allow the chipset to monitor the battery’s status in real-time and take necessary actions. This plays an important role in ensuring the safety and lifespan of the battery.

Core know-how of charging control firmware for Samsung 21700 50E / 7S 20P battery cell with NXP MC33771C chipset

The NXP MC33771C chipset is a high-performance battery cell controller that can simultaneously monitor and control the charging and discharging of 14 cells. Our company has analyzed the firmware design structure that can precisely measure and manage the voltage, current, temperature, remaining amount, life, etc. of the Samsung 21700 50E / 7S 20P battery cell using this chipset.

Our company’s firmware has the following features:

It sets the optimal charging voltage and current for each cell, and balances the cells to enhance the performance and lifespan of the battery. It detects the temperature of the cell in real-time, and adjusts or stops charging to prevent overheating or overcharging. It accurately predicts the remaining amount and life of the cell, and communicates with smartphones or computers via LED or LCD display or Bluetooth or WiFi.

Deepnetwork, a one-person company, applied the evaluation board to control the charging of Samsung 21700 50E / 7S 20P battery cells

The EVB evaluation board is a board that can evaluate and test the functions and performance of a battery cell controller using the NXP MC33771C chipset. Our company has detailed analysis of developing and verifying the charging control technique for Samsung 21700 50E / 7S 20P battery cells using this board.

Our company’s charging control technique has the following features:

It optimizes the charging curve according to the characteristics and requirements of the Samsung 21700 50E / 7S 20 P battery cell, and improves charging efficiency and safety. It minimizes the heat generated during charging, and monitors and diagnoses the charging state by analyzing the internal resistance and chemical reaction of the cell. It stores and analyzes the data generated during the charging process to evaluate and improve the quality and reliability of the battery.

In active cell balancing, energy is extracted from overcharged cells and moved to low-voltage cells. For this, the active balancing circuit uses switches and resistors between each cell. These circuits control the switch according to the voltage state of each cell to move energy.

The switch control algorithm is as follows:

Voltage monitoring: The firmware periodically monitors the voltage of each cell. This period is determined according to the system requirements and the characteristics of the battery.

Overcharge cell detection and energy movement: When an overcharged cell is detected, the firmware controls the switch between the cell and the low-voltage cell to move energy. This helps maintain the voltage of the cell within a safe range and minimize the voltage difference between cells.

These algorithms must go through a rigorous design and verification process according to ASIL D standards. The verification procedure must include system-level verification that tests electromagnetic compatibility, electrostatic discharge, transient immunity, and communication reliability in harsh environments.

In the firmware design using the NXP MC33774 chipset, the control algorithm for active cell balancing is as follows:

Active balancing circuit design: Active cell balancing is a method of extracting energy from overcharged cells within the battery pack and moving it to low-voltage cells. For this, the active balancing circuit uses switches and resistors between each cell. These circuits control the switch according to the voltage state of each cell to move energy.

Voltage monitoring: The firmware periodically monitors the voltage of each cell. This period is determined according to the system requirements and the characteristics of the battery. Generally, this period is determined considering various factors such as charging state, battery temperature, cell connection status, etc.

Switch control algorithm: The firmware implements an algorithm to control the switch to move energy from overcharged cells to low-voltage cells. This algorithm monitors the voltage state of each cell and controls the energy movement between overcharged cells and low-voltage cells. This allows you to minimize the voltage difference between cells and maintain the voltage of the battery pack uniformly.

These algorithms must go through a rigorous design and verification process according to ASIL D standards. The verification procedure must include system-level verification that tests electromagnetic compatibility, electrostatic discharge, transient immunity, and communication reliability in harsh environments.

The NXP MC33774 chipset provides a maximum cell balancing current of 300 mA for each cell. This means that each battery cell can independently balance through a maximum current of 300 mA.

The control algorithm for passive cell balancing is as follows:

Voltage monitoring: The firmware periodically monitors the voltage of each cell. This period is determined according to the system requirements and the characteristics of the battery. Generally, this period is determined considering various factors such as charging state, battery temperature, cell connection status, etc.

Overcharge cell detection: The firmware analyzes the monitored voltage data to detect overcharged cells. Overcharged cells are cells whose voltage is higher than a certain threshold.

Current leakage: When an overcharged cell is detected, the firmware lowers the voltage by letting current flow through the resistor connected to the cell. This helps maintain the voltage of the cell within a safe range and minimize the voltage difference between cells.

These algorithms must go through a rigorous design and verification process according to ASIL D standards. The verification procedure must include system-level verification that tests electromagnetic compatibility, electrostatic discharge, transient immunity, and communication reliability in harsh environments.

 

Are there any professional development companies that have confirmed operation without problems during the stringent international safety certification when charging control with the battery cell controller chipset? It seems that a complex detailed safety verification process is necessary to ensure that the firmware and circuit design are definitely completed without any problems in accordance with this certification standard. I wonder if there is a company that is confident that there is no problem with this stringent international certification. After detailed review, it is quite tricky, so I leave additional opinions like this …

 

Deep Network, a one-person startup specializing in consulting for electric vehicle battery charging control  

E-mail : sayhi7@daum.net    

Representative of a one-person startup /  SeokWeon Jang