BMS Battery Management System
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BMS Battery Management System

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BMS Refers to Battery Management System

Why lithium battery needs BMS? Lithium batteries have poor safety and sometimes have defects such as explosions (see appendix for more details)

A BMS wiring diagram of a “Main-Sub System” structure(as pic shows)

Protective Circuit of MOS in Charge and Discharge Circuit

In the MOS tube of the BMS charge and discharge circuit, the sudden current of the switch generates a peak voltage of the drain, which damages the MOS tube. The faster the power tube switching speed, the higher the overvoltage generated. In order to prevent device damage, a high-power TVS tube will be added between the GS.



TVS diode- SMCJ series is strongly recommended,The selection is based on the highest voltage of the battery and the withstand voltage of the MOS.

Voltage of Battery GS pole protection tube Package Form Protection tube power
11V Battery(3 strings) SMCJ15CA SMC/Do-214AA 1500W
14.4V Battery(4 strings) SMCJ18CA SMC/Do-214AA 1500W
18V(5 strings) SMCJ22CA SMC/Do-214AA 1500W
21V(6 strings) SMCJ24CA SMC/Do-214AA 1500W
25V(7 strings) SMCJ33CA SMC/Do-214AA 1500W
36V(10 strings) SMCJ45CA SMC/Do-214AA 1500W

TVS diode- 5.0SMDJ series is strongly recommended. Selection is based on the highest voltage of the battery and the withstand voltage of the MOS.

Voltage of Battery GS pole protection tube Package Form Protection tube power
48V Battery(14 strings) 5.0SMDJ60CA SMC/Do-214AB 5000W(Industrial/automotive grade)
58V Battery(16 strings) 5.0SMDJ75CA SMC/Do-214AB 5000W(Industrial/automotive grade)
64V(18 strings) 5.0SMDJ85CA SMC/Do-214AB 5000W(Industrial/automotive grade)
72V(20 strings) 5.0SMDJ90CA SMC/Do-214AB 5000W(Industrial/automotive grade)
ESD Protection of CAN BUS

D8 commonly used materials:ESD24VAPB

RS485 Selection

Commonly used protective devices

Selection Guide Application Package
ESD712 Small battery, fixed in a metal box, the scene where the signal line number uses a shielded wire externally SOT-23,7V or 12V
SMF6.5CA Similar to fingerprint lock, smart home products SOD-323
SMAJ6.5CA The control of electric bicycles and mopeds, e.g.: Yadi, Xinri, Mavericks, etc., there are often plug-in and commissioning operations during installation. SMA/Do-214AC
SMBJ6.5CA Electric energy storage power supply,solar energy storage products SMB/Do-214AA
Extended knowledge

Why do lithium batteries need a BMS management system? Lithium batteries have poor safety and sometimes have explosion defects. In particular, lithium batteries with lithium cobalt oxide as the positive electrode material cannot be discharged at a large current, and the safety is poor. In addition, almost all types of lithium batteries overcharge or overdischarge will cause irreversible damage to the battery cells. Lithium batteries are also extremely sensitive to temperature:

If it is used in an excessively high temperature, it may cause the electrolyte to decompose, burn or even explode; too low the temperature will cause the performance of the lithium battery to deteriorate significantly, affecting the normal use of the device.

Due to the limitations of the manufacturing process of lithium batteries, the internal resistance and capacity of each battery cell will be different. When multiple battery cells are used in series, the charge / discharge rate of each battery cell will be inconsistent, which leads to a low utilization rate of battery capacity. In view of this, the lithium battery usually needs a special protection system to monitor the health status of the battery in the actual use process, so as to manage the use process of the lithium battery.

The lithium battery management system can effectively carry out effective monitoring, protection, energy balance and fault alarm on the lithium battery pack, thereby improving the working efficiency and service life of the entire power battery pack. Lithium batteries are widely used in various precision equipment because of their many advantages such as high working voltage, small size, light weight, large energy density, no memory effect, no pollution, small self-discharge, and long cycle life.

The principle of BMS power lithium battery management system:

Lithium battery management system (BMS) determines the status of the entire battery system by detecting the status of individual cells in the power battery pack, and performs corresponding control adjustments and strategy implementation on the power battery system according to their status to achieve power lithium Charge and discharge management of the battery system and individual cells to ensure the safe and stable operation of the power battery system.

The topology structure of a typical lithium battery management system is mainly divided into two major blocks: a master control module and a slave control module. Specifically, it consists of a central processing unit (main control module), a data acquisition module, a data detection module, a display unit module, control components (fuse devices, relays), etc.

Generally, the internal CAN bus technology is used to realize data information communication between modules.

Based on the functions of each module, BMS can detect the voltage, current, temperature and other parameters of the power lithium battery in real time, realize thermal management, balanced management, high voltage and insulation detection of the power battery, and can calculate the remaining capacity of the power battery, charge and discharge power And SOC & SOH status.

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