2023-06-01
With the formulation and promotion of China's strategic goal of "carbon peaking, carbon neutrality", the proportion of clean energy such as photovoltaic , wind power and power from energy storage systems will be significantly increased, which has brought huge development space for the energy storage market.
The main technical route in electrochemical energy storage is lithium-ion battery energy storage, and lithium-ion battery PACK technology is an important part of industry skills. Below, let's learn some basic knowledge of battery PACK with CTS.
1. Definition
Lithium ion battery PACK is a manufacturing process for lithium-ion batteries, which means packaging, packaging, and assembly. It refers to the connection of multiple lithium ion battery celsl groups in series, taking into account system mechanical strength, thermal management, BMS matching, and other issues. Its important technologies are reflected in overall structural design, welding and processing process control, protection level, and active thermal management system. If two batteries are connected in series or parallel to form a specific shape according to customer requirements, it is called a PACK.
2. Composition of battery pack
The battery pack consists of several important components, including individual battery modules, electrical systems, thermal management systems, cabinets, and BMS .
▶ Battery module: If battery PACK is compared to a human body, then the module is the "heart" responsible for storing and releasing electrical energy.
▶ BMS: Battery management system can be seen as the "brain" of batteries. Mainly responsible for measuring parameters such as voltage, current, and temperature of the battery, as well as balancing functions. Data can be transmitted to MES.
▶ Electrical system: mainly composed of connecting copper strips, high-voltage harnesses, low-voltage harnesses, and electrical assurance devices. The high-voltage harness can be seen as the "artery" of the battery PACK, transmitting the battery power to the end load continuously, and the low-voltage harness can be seen as the "neural network" of the battery PACK, transmitting the detection signal and control signal in real time.
▶ Thermal management system: There are two main methods of thermal management system: air cooling and liquid cooling, and liquid cooling can be divided into cold plate liquid cooling and immersion liquid cooling. The thermal management system is equivalent to installing an air conditioner for the battery pack. The battery generates heat during discharge mode. To ensure that the battery operates at a reasonable ambient temperature and improve its cycling life, the system temperature difference is generally required to be ≤ 5 ℃.
▶ Box: mainly composed of box, box cover, metal bracket, panel and fixing screws, it can be regarded as the "skeleton" of battery PACK, playing the role of support, resistance to mechanical shock, mechanical vibration and environmental protection.
CTS 48V 5kwh lifepo4 battery module
3. Characteristics of battery pack
▶ PACK lithium battery packs require high consistency in battery capacity, internal resistance, voltage, discharge curve, and lifespan.
▶ The cycle life of the battery pack PACK is lower than that of a single battery.
▶ Used under limited conditions (including charging, discharging current, charging method, temperature, etc.)
▶ After the lithium battery pack is formed, the battery voltage and capacity have greatly increased, and it must be protected by charging balance, temperature, voltage, and overcurrent monitoring.
▶ The battery pack must meet the voltage and capacity requirements required by the design.
4. PACK method
▶ Series parallel composition: The battery module is composed of individual cells connected in series. Parallel connection increases capacity, voltage remains unchanged, and after series connection, voltage doubles, capacity remains unchanged. For example, if 16 cells with a voltage of 3.2V are connected in series, it is 51.2V, which is called series boosting. For example, if two cells with a capacity of 50Ah are connected in parallel, there will be 100Ah, which is called parallel expansion.
▶ Battery requirements: Select the corresponding battery cells according to your own design requirements. The types and models of batteries in parallel and series should be consistent, and the differences in capacity, internal resistance, and voltage values should not exceed 2%.
▶ PACK process: The battery can be PACKed in two ways. One is laser welding, ultrasonic welding or pulse welding. This is a common welding method, which has the advantage of good reliability but is not easy to replace. The second is through contact with elastic metal sheets, which has the advantage of no welding and easy battery replacement. The disadvantage is that it may lead to poor contact. Considering the production yield, efficiency, and internal resistance of the connection point, laser welding is currently the preferred choice for many battery manufacturers.
5. How to understand the technical parameters of battery PACK
| Items | parameters | marks |
| Combination method | 1P16S | |
| Rated capacity | 100Ah | |
| Rated voltage | 51.2V | |
| total energy | 5.12kWh | |
| Discharge rate | 1C | |
| weight | 45±0.5kg |
▶ Combination method: 1P16S
Interpretation: S represents series cells, P represents parallel cells, and 1P51.2S represents 16 series and 1 parallel cells. After series connection, the voltage is doubled, and the rated voltage is 3.2 * 16=51.2V.
▶ Rated capacity: 100Ah
Interpretation: The rated capacity of a battery refers to the capacity of a battery to operate continuously for a long time under rated operating conditions. The rated capacity C of a battery, in ampere hours (Ah), is the product of the discharge current in amperes (A) and the discharge time in hours (h). So 100Ah represents discharge at a maximum current rate of 0.5C, which can last for 2 hours.
▶ Rated energy: 5.12kWh
Interpretation: Rated energy (Wh)=nominal capacity
(Ah) * nominal voltage (V), so the total energy that a battery can release is related to both capacity and voltage.
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