Detailed explanation and trend analysis of energy storage battery parameters

The rapid growth in installed capacity of energy storage systems has made the energy storage field a new competitive battlefield for battery manufacturers. Whether it is diversifying from the electric vehicle (EV) market or focusing on battery energy storage systems, it is an attractive opportunity for battery suppliers to take advantage of the strong development in the next decade.

The battery is the most important part of the electrochemical energy storage system, accounting for 60% of the cost of the energy storage system. PCS makes up 20%, EMS makes up 10%, BMS makes up 5%, and other accessories make up 5%. According to relevant data, the shipment volume of storage batteries in China is maintaining a high-speed growth trend, with an average annual growth rate of over 50% in the next three years.

The turning point of energy storage industrialization is accelerating. Since the beginning of this year, multiple battery companies have signed large orders for energy storage batteries, and the layout of energy storage battery production capacity is being intensively carried out.

According to incomplete statistics from Battery China, at the beginning of the new year, domestic battery companies have deployed over 200GWh in energy storage battery projects.

Classification and performance parameters of energy storage batteries

Energy storage batteries are the core component of energy storage systems, accounting for approximately 60% of the total cost of energy storage systems. Unlike power batteries, energy storage batteries are widely used in power systems such as power generation, transmission and distribution, and electricity consumption due to their functions of peak shaving, valley filling, system frequency regulation, and smooth new energy power output. According to downstream application directions, it can be divided into three directions: power generation side (to solve the problem of grid instability caused by the intermittency and volatility of wind and solar power generation), grid side (to maintain stable operation of the grid), and user side (to cut peak and valley periods and save user electricity costs).

At present, lead-acid batteries and lithium batteries are widely used.

Main performance parameters of the battery

48V Energy Storage Lithium Battery Parameters (Paineng US 2000)

1. Ah (ampere hour)

Reflecting the size of the battery capacity, for example, 48V100Ah represents a battery capacity of 4.8 kWh. The nominal voltage and nominal ampere hour are the most fundamental and core concepts of a battery. Electricity Wh=power W * hour h=voltage V * ampere hour Ah

2. C (battery discharge rate C)

Reflecting the rate of battery charging and discharging capability. Charge discharge rate=charge discharge current/rated capacity. A measure of the speed of discharge. Generally, the capacity of a battery can be detected by different discharge currents. For example, a battery with a capacity of 100A · h has a discharge rate of 0.15C when discharged at 15A.

3. Depth of Discharge (DOD)

Refers to the percentage of the capacity released by the battery during use compared to the rated capacity of the battery. The DOD depth set for the same battery is inversely proportional to the battery cycle life. When improving one aspect of performance, it sacrifices the performance of other aspects.

For example, with a DOD of 80%, the cycle life of lithium batteries can reach 6000 to 12000 times.

The relationship between DOD and battery cycle times

4. State of Charge (SOC)

Indicates the percentage of remaining battery power to the rated capacity of the battery.

5 SOH（State of Health）

The health status of a battery (including capacity, power, internal resistance, etc.) is the ratio of the capacity released by the battery when discharged at a certain rate from a fully charged state to the cut-off voltage to its corresponding nominal capacity.

Simply put, the ratio of performance parameters to nominal parameters of a battery after a period of use is 100% for newly manufactured batteries and 0% for completely scrapped batteries. According to IEEE standards, if the capacity of a battery when fully charged after a period of use is less than 80% of its rated capacity, the battery should be replaced.

6. Three-stage approach

Generally refers to a device that charges in three stages. Three stage charging is an automatic charging process, and constant current, constant voltage, and float charging are the three necessary stages of three-stage charging.

Development trend of energy storage batteries

Lithium ion batteries are gradually replacing lead-acid batteries

Batteries are a highly efficient way of energy storage. Lithium ion batteries have the advantages of low environmental pollution, high energy density, long cycle life, and strong rate performance. As their cost decreases, the economy of lithium-ion batteries is becoming increasingly prominent, and their application in the energy storage market is becoming more and more widespread. Newly built battery energy storage facilities are increasingly adopting lithium-ion batteries, and existing lead-acid batteries are gradually being replaced by lithium-ion batteries. In the future, the development prospects of the energy storage lithium-ion battery market are promising.

Lithium iron phosphate batteries are highly favored

In energy storage lithium-ion batteries, lithium iron phosphate batteries have more advantages than ternary material batteries and are the mainstream direction of future lithium-ion battery development. The main reason is that energy storage batteries mainly focus on the economic efficiency of battery production and use, and consider factors such as battery cost, cycle performance, and full life cycle cost more. Therefore, lithium iron phosphate batteries are highly favored due to their advantages such as low production costs and high cycle times.