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Welcome to learn about the knowledge of Li-ion Battery series. From the previous articles, we have introduced a series of topics about the Li-ion Battery cells. Just like the blood travels throughout our body to give us energy, Li-ion battery cells are the power center which store energy and provide full power for the electronic device. But without the cooperation with body organs, blood does not make sense in our body. So do the Li-ion battery cells. We will discuss the four basic components of building a Lithium-ion battery pack.
From the chart below, we could have a intuitive grasp of the typical components found in a battery pack:
1. Battery Cells
2. BMS (Battery Management System)
3. Connection System (Connector, wires, pigtail)
4. Battery Enclosure (PVC heat shrink, Plastic, Metal)
Let’s discover each part of a Li-ion battery pack in detail.
1. Battery Cells
In previous article, we have known that Lithium-ion battery cells are the essential part of the entire battery pack. There are four types of battery cells, including button cells, cylindrical cells, pouch cells and prismatic cells. According to different chemistry types, the cathode materials which have been used to achieve battery performance include Cobalt-based lithium-ion (LCO), Lithium iron phosphate (LFP), lithium manganate (LiMn2O4), ternary materials such as Nickel Cobalt Aluminum (NCA) Nickel Cobalt Manganate (NCM or NMC). LTO is alternative anode material to graphite/carbon. When it comes to high power applications, a single lithium-ion cell is hard to supply power for these application because of the insufficient voltage and capacity. In order to meet this requirement, combining lithium-ion cells in series or in parallel in lithium-ion battery pack is necessary so as to elevate the voltage and capacity for delivering sufficient power. The cells is the key component to store energy and provide power for the operation of device. However, assistance from other components in the battery pack is required.
Due to the special material of lithium battery, it is easy to cause safety failure without protection component. Therefore, a BMS (Battery Management System) is necessary to prevent the battery pack from damage. The BMS is a control system of the Li-ion battery pack which could contain hardware and software. It could be simple or equip with complex function relying on the requirement of battery pack and application. Similar to our brain that control and make our body function properly, the BMS in the battery pack monitors the battery cells’ status and make sure the energy carried through the battery cells inside a battery pack in a controlled and safe way. Battery Management System offers a variety of function including monitoring of battery status (capacity, SOC, voltage, temperature,…), management of charge and discharge, thermal management, balancing management, failure warning, just to mention a few. The users could find more information of the battery such as low battery life through data transmission from the BMS in battery pack.
3. Connection System
Now, we have a basic understanding of the battery cells and BMS, but how do these components work together? This is where the connection system comes into play. The Nickel strips are common used component to connect battery cell, which carry large amounts of current and can be attached to the cell without overheating. These strips ensure the energy transmission. After the preparation of nickel strips, welding and bolting are two mainly used methods for connecting a number of battery cells together. Additionally, wires, pigtail, and connector are the other vital components to building a lithium-ion battery pack.
4. Battery Enclosure
Last but not least, while all these components are assembled properly together, a battery enclosure to package them is required so as to protect the battery cells as well as be able to be installed into a device. They can be either sealed with heat shrink such as PVC heat shrink or packaged in a hard case like plastic housing and metal housing. The enclosure is a protective covering to ensure the safe and proper installation of battery components and provide a clean package for the user. The selection of battery enclosure lies in the device requirement. The location of battery pack inside the device and the working environment will both affect the selection of battery housing.