What does a battery management system do - the best guide for BMS

1. What is battery management system

① Definition of BMS

BMS is the abbreviation of battery management system, which is the brain of the power battery system, used to manage the battery so that the battery can maintain a better condition and work stably.

② Role of BMS

The battery management system is closely integrated with the battery to detect the voltage, current and temperature of the battery at all times. And it also carry out leakage detection, thermal management, battery balance management, alarm reminding, calculate the remaining capacity, discharge power, report SOC & SOH status, and control the maximum output power with algorithm to get the maximum driving range according to the voltage, current and temperature of the battery, and control the charger with algorithm for the best current charging.

It also uses algorithms to control the maximum output power to get the maximum driving range based on the battery voltage, current and temperature, and algorithms to control the charger for optimal current charging, and communicates with the vehicle total controller, motor controller, energy control system and vehicle display system in real time through CAN bus interface.

2. The role and necessity of battery management system

① Role in three areas

• Sensing (state management), sensing the state of the battery, is the basic function of battery management system. Voltage measurement, resistance measurement, temperature measurement, all to sense the battery state.
• Management (balance management), the most basic is the balance management, thermal management. The purpose is to use the battery as well as possible.
• Protection (safety management), if the battery is out of condition, the battery management system will protect it and alarm upwards.

② Necessity

Overcharging and overdischarging are fatal to lithium-ion batteries, which can lead to battery damage, capacity reduction, and life reduction. In serious cases, bursting and fire will also occur. Lithium-ion batteries are more likely to be overcharged and overdischarged when used in groups, and the root cause of this is the difference in the consistency of the batteries. These differences, if not properly controlled in the charging and discharging process, will further increase and lead to part of the battery overcharge, overdischarge, which in turn causes a sharp decline in battery capacity and life, and eventually cause accidents. This is a necessity for BMS for lithium ion battery.

3. What types of battery management system are there

4. Function and design of battery management system

① Main functions

● Real-time monitoring of battery status.

Estimation and monitoring of the internal state of the battery (such as capacity and SOC, etc.) by detecting the external characteristics parameters of the battery (such as voltage, current, temperature, etc.) and adopting appropriate algorithms, which is the basis and key to the effective operation of the battery management system.

● Thermal management, battery equalization management, charge or discharge management, fault alarm, etc., after correctly acquiring the state of the battery.

● Establish communication bus to realize data exchange to display system, vehicle controller and charger, etc.

② Design and module functions

• Power supply module: provide stable power supply to various power-using devices
• MCU module: collect, analyze data, send and receive control signals
• Relay control module: control whether to supply power to the battery pack by controlling the suction and disconnection of the relay
• Current detection module: collects the charging and discharging current of the battery pack during charging and discharging
• Voltage detection module: measure the voltage of each module of the battery pack

• Temperature detection module: detects the battery pack temperature during charging and discharging
• Equalization control module: control the battery equalization
• Total voltage and insulation detection module: monitor the total voltage of the power battery pack and whether the insulation between the battery pack and the vehicle body meets the requirements
• CAN transceiver module: for data communication and program calibration and diagnosis between other controllers and MCU, coordinating the communication between the vehicle control system and MCU
• RS232 transceiver module: used for battery pack management system status monitoring, program calibration and parameter correction

5. Why battery management system is so important - features and advantages of BMS

● Protection function (BMS monitors the status of each battery cell and deals with serious situations): Delays the life of the battery cell and ensures safe use.

• Over-voltage protection (avoid over-charging or over-discharging) Undervoltage protection
• Over-current protection (to avoid over-current and short-circuit)
• Over-temperature protection (to prevent damage to the battery and extend the life of the battery pack)
• Leakage protection

● Performance: high energy and fast response time.

• Advanced battery equalization function (battery equalization processing can ensure consistent state of charge between different cells, avoid individual cells being overcharged when charging and overdischarged when discharging, and the full equalization process can maximize the capacity of the battery pack.)
• Reusable
• Fast processing of short-circuit events within 260ns

● Management functions: Application device interface

• RS232 interface
• CAN bus interface
• Historical fault record

6. Industry background of battery management system

① Origin of BMS

The scarcity of petroleum fuels and the rampant greenhouse effect have determined that current fuel-driven vehicles are not sustainable. And electric vehicles will gradually replace traditional cars as the main transportation mode in at least 50 years. Lithium batteries, with many advantages such as small size, light weight, long life, no pollution, and high safety performance, will be highly expected.

Electric transportation is the biggest test of the lithium industry, with the gradual maturity of the field of electric transportation and forced to lead-acid batteries on the huge pressure of environmental pollution, the field of communications and energy storage will gradually replace the lead-acid batteries with lithium batteries, and battery manage system as the power and storage of lithium batteries must support the product will also further penetrate the market.

② Market positioning

Four levels of BMS: automotive-grade BMS / power tools / laptop and cell phones / industrial machinery segment after market changes

7. Battery management system related research and latest development

① Research in China and other countries

Advanced technology is mainly mastered by European and American countries, for example, General Motors in the United States uses microcomputer to manage the battery. France and Siemens in Europe have developed management systems that can track the battery characteristics curve to protect the battery. Honda and Toyota in Japan have developed a high-voltage safety detection system that will immediately cut off the power to ensure the safety of electricity if the electric vehicle is in a collision.

China attaches great importance to the development of new energy electric vehicles, and it is listed as a national high-tech research project in the "Tenth Five-Year Plan", as well as a national "863" science and technology research project. Many energy storage BMS companies are deploying battery management systems. The battery management system and the charger system have been researched and developed for a long time, and a great breakthrough has been made in BMS, which is close to the foreign level, and the products developed are used in a large number of pure electric vehicles (EV) and hybrid electric vehicles (HEV).

② Application and development

● Battery management system application direction

• Electric transportation (pure electric/hybrid/quick charge and quick change)
• Communication base stations (UPS backup power/switching power)
• Coal Mine Safety (Refuge / Life-Saving Cabin / Tractor)
• Energy storage power station (solar power generation / wind and solar complementary power generation)

● Battery management system development direction

In the future, the battery management system will continue to play a vital role in the safety of power-using equipment, optimizing battery pack performance, extending battery pack life, improving battery pack usage efficiency, and reducing product operating costs. Its market size will expand in parallel with the lithium battery in the field of power and energy storage. It is predicted that the demand market for battery management system will reach more than 36 billion in 2020, which is 160 times of the current market capacity, with an average annual growth rate of 67%.

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