Basic Principles of Battery Energy Storage System Design: Safety First

Crystal Battery Storage

From a technical perspective, we should focus on the following aspects of security issues.

1. The safety of the battery cell

① At present, most of the lithium battery energy storage systems use lithium iron phosphate batteries. The cathode material of commercial lithium iron phosphate batteries has high safety and stability, and it still has high stability and storage performance even under high temperature conditions. 

② For the negative electrode material, graphite has good thermal and electrical conductivity and is called a semi-metal.

③The separator is mainly a polyolefin microporous membrane, which has a stable chemical structure, excellent mechanical strength, and good electrochemical stability.

④The electrolyte of lithium-ion batteries is basically an organic carbonate substance, which is a type of flammable substance. Adding flame retardants with high boiling point and high flash point to the electrolyte can significantly improve the safety of lithium-ion batteries.

2. Electrical safety design

In order to ensure that no electrical safety accidents occur during the use of lithium battery energy storage products, the product development process must pay attention to electrical safety design and verification.

①Insulation protection

The battery core itself has its own insulating blue film, and a PET film is attached to the bottom of the film block to meet the insulation and voltage requirements.

②Open circuit and short circuit protection

In the entire battery system, contactors, molded case circuit breakers and fuses are designed respectively for safety protection.

③Direct contact protection

Direct contact protection mainly includes electrical insulation and shielding protection.

④Indirect contact protection

The design of indirect contact protection mainly includes equipotential, electrical clearance and creepage distance design.

The system box must be connected to the earth at equal potential, and the connection impedance should not exceed 0.4Ω. All accessible conductive metal parts in the battery system must be equipotentially connected to the earth.

3. Structural safety design

①Battery module level

All design solutions adopt flame retardant fuel solutions. Voltage collection points are arranged on each battery cell, and temperature collection points are reasonably allocated to realize real-time and reliable monitoring of the operating status of the battery system.

②Battery cluster level

At the battery cluster level, protective insulation materials are added at the bottom support position to enhance insulation and protection properties. Additional cooling air ducts are provided to achieve efficient temperature control and improve system safety performance.

③System level

A pressure relief device is installed to maintain the fire extinguishing concentration in the fire extinguishing area and protect the maintenance structure from damage.

4. Operational safety management

①Multi-level monitoring

The battery system is equipped with a multi-level architecture battery management system, which collects various parameters such as battery voltage and temperature in real time, and monitors and makes judgments in real time, such as excessive temperature, excessive temperature rise, excessive temperature difference, voltage fluctuation, abnormal current, monitoring alarms, etc.

②Real-time warning

Through the multiple composite fire detection system, early warning and timely intervention of the fire extinguishing system can effectively avoid heat spread.

③Passive protection

Adopt efficient ambient temperature control, complete structural design and complete electrical design and selection.

④Active protection

A gas fire extinguishing system and total flooding fire extinguishing method are used to ensure that when a battery fire occurs, the fire extinguishing agent can quickly fill the entire protective area through the pipe network system and submerge the fire point, improving the pertinence and reliability of the fire extinguishing system.

After the principle of safety first, we also need to uphold the principle of high reliability and economy.

Controlling details and adhering to principles are the foundation for long-term stable operation of energy storage systems.