Manufacturing Process of Car Batteries

Ordinary as battery may look, its manufacturing process could be quite complicated. In this post, we’ll show you how a battery is produced from the very beginning with the example of the finished vehicle battery. Hope you could know more about the power source after reading it.

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1. How was a cell of battery born?

The cell is the smallest unit of a battery system. A collection of batteries form a module, and then the collection of these modules form a battery pack. This is the basic structure of the vehicle power battery.

1.1 Pulping of active materials – mixing

Mixing process is to stir the active material into a slurry by a vacuum mixer. This is the first process of battery production. The quality control of this process will directly affect the quality of the battery and the qualified rate of the finished product.

1.2 Applying the stirred slurry to the copper foil – coating

The process is to apply the slurry that has been stirred after the previous operation to a 4000-meter-long copper foil at a speed of 24 feet per minute. The copper foil before coating is only 6 microns thick.

1.3 Pressing and splitting the cathode material on the copper foil – cold pressing and pre-cutting

In the milling workshop, the roller is used to press the pole piece to where the positive and negative electrodes are attached, and the cold-pressed pole pieces are cut as per the size of the battery to be produced.

1.4 Cutting out the positive and negative electrodes on the battery – die cutting and slitting

The die cutting process is to form a conductive electrode tab for a battery cell by a die cutting machine. The polar tab is the metal conductor derived from the positive and negative poles in the cell. The slitting process is to cut the battery pole piece by a cutter.

1.5 Finishing the prototype of the battery cell – winding

Combining the positive electrode sheet, the negative electrode sheet and the separator of the battery into a bare cell in a winding manner.

1.6 Removing moisture and injecting electrolyte – baking and injecting

Moisture is the enemy of the battery system. The battery baking process is to make the water inside the battery up to the standard and ensure that the battery has good performance throughout the life cycle. The injection is to inject electrolyte into the cell.

1.7 The process of cell activation – formation

The formation is a process of activating the cell after the injection, and chemical reactions inside the cell, by charging and discharging, form a SEI film (the electrolyte and the anode material react on the solid-liquid phase, so a passivization film is formed). The process also includes the second injection of electrolyte, weighing, welding of the injection port and gas tightness testing after the cell is activated.

2. Battery pack production process

A single battery cell cannot be used directly. Only when a lot of cells are combined, together with protective circuits and shells, can they be used directly. This is the so-called battery module.

2.1 Feeding

The battery cell is transmitted to the setting position, and the robot automatically grabs it and send it to the mold assembly line.

2.2 Plasma cleaning process

Cleaning the surface of each cell. Ion cleaning is used here to ensure that contaminants in the process are not attached to the bottom of the cell.

2.3 Gluing for the cell

Before the cell is assembled, the surface needs to be glued. This is how the battery is fixed, insulated and dissipate the heat.

2.4 Welding of end plate and the side plate

The battery modules are mostly made of aluminum end plates and side plates, which are later laminated and welded by robots.

2.5 Assembling of wire Harness isolation board

After the welding monitoring system accurately locates the welding position, the material barcode of the wire harness isolation plate is bound to Manufacturing Execution System, and a separate encoding is generated for traceability. After the coding, the harness isolation board is automatically loaded into the module by the robots.

2.6 Completing the serial-parallel connection of the battery – laser welding

Through automatic laser welding, the connection between the pole and the connecting piece is completed, and thus the battery serial parallel is possible

2.7 An important test before shipping – offline test

Check the full performance of the module before it goes off the production line, including module voltage/resistance, battery cell voltage, withstand voltage tests, and insulation resistance test.

3. Battery pack’s ultimate test – battery pack safety test

In fact, from the initial design stage, electric vehicles have to adopt various methods to ensure maximum safety. However, the perfect design has to be tested by practice.

3.1 Fire test

In terms of safety performance, the standard in China is external combustion for 130 seconds, and the battery can’t be lit up or explode.

3.2 Vibration test

Vibration test is used to simulate the bumpy road conditions of battery packs in actual use. It is used to test whether the vibration of battery packs can cause the parts of battery products with poor quality to loosen or even cause the shell to break down.

3.3 Impact test

Similar to vibration test, impact test is used to test the mechanical stability of battery pack. It simulates the impact of instantaneous bump on battery pack structure when a vehicle passes through a road barrier.

3.4 Squeeze test

As for the pass standard of extrusion testing, the battery can’t catch fire or explode.

If you are interested in learning more about batteries, please feel free to contact us or leave a comment. We’d be very happy to hear from you.

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