18650 lithium battery pack customization tutorial
18650 lithium ion battery pack How should be assembled?
18650 lithium battery pack can be used for rechargeable and high current consumption devices. Due to its versatility, 18650 lithium-ion batteries are often used in a variety of applications, including electric vehicles/scooters, mobile power supplies, and practical devices such as emergency lighting and flashlights, so there are many benefits to learning to assemble 18650 lithium battery pack by yourself.
First, we screen the 18650 cells for voltage, internal resistance, and capacity, also known as capacity separation. As for capacity, after the materials are prepared, the battery is assembled, and then the voltage and internal resistance are selected. The usual selection criteria are a voltage difference of 5 millivolts and an internal resistance difference of 3 meters.
Only when there is a voltage difference and a resistance difference can the battery be assembled into a set of batteries, so that the battery stability will be better and the battery performance will be better. The device used is a core separation device.
Assemble the battery cells in series and parallel
When assembling the battery, it is best to install a bracket with a battery cell. After the assembly is completed, there will be a bracket inside the battery. On the one hand, the heat dissipation of the battery is much better than that of a battery without a battery. On the other hand, the structure of the battery is also independent, and the battery is safer, and the safety of the battery will not be affected by vibration.
Welding of the battery pack
The material used for spot welding is nickel strip, which is divided into pure nickel strip and nickel-plated steel strip. The price of pure nickel is much higher. The advantages are low internal resistance, large current, and not easy to rust. In contrast, the cost of nickel-plated steel plate is much lower, but the disadvantage is that the internal resistance is large, the flow is small, and it is easy to rust.
Nickel Strip Thickness Selection
For the thickness of the nickel strip, in traditional products, a thickness of 0.15 mm is usually require, so that the power of the spot welder is greater. If the current is low, use a 0.1 mm thick nickel strip. If the current is particularly large, use a 0.2 mm nickel strip. It is not recommended to use nickel sheets that are too thin or too thick.
When spot welding, attention should be paid to the spot welding effect. Do not make the power of the spot welding machine too low to cause the battery core to be welded, and do not make the power of the spot welding machine too high to cause the spot welding to burst. After spot welding, it passed the 7 KG tensile test.
Protect the battery pack
The ternary lithium 13 series 48 V lithium battery protective cover is used. The welding requirements of the protective cover are carried out according to the instructions of the protective cover. Starting from B-, B0, B1, and B13, they must be welded according to the requirements of the protective cover.
After welding the leads of the BMS protection board, the solder joints should be insulated with heat shrink tubing to prevent short circuits.
What is BMS?
The battery management system (BMS) monitors the battery pack, which is electrically grouped in a row x column matrix to provide a specific range of voltage and current within a set time period in response to the expected load conditions. The supervision of BMS usually involves the following:
Calculation of the state of charge
Overvoltage and undervoltage protection of the battery.
Balanced charging.
Battery pack charging management.
Temperature monitoring of the pack.
Plastic battery pack insulation packaging
This step is to insulate and shape the battery, and then pack the battery wires and packages, so that the battery assembly process can be better isolated, and then PVC film is apply to the battery to prevent water and dust from entering, thereby protecting the battery.
Put the battery pack into the chassis
This step requires connecting the exposed wires of the battery pack to the shell connector of the shell, including charging, discharging, fusing, switching, etc. The current of the ordinary charger port is low, so the wire diameter is thinner; because the current of the discharge port is large, a thicker wire is used to make the overcurrent more ideal. The welding wire must be designed according to the structural diagram of the battery pack and the chassis.
The last battery test
The final test content includes: lithium battery charge and discharge cycle, capacity, internal resistance, open circuit voltage, overcurrent, overcharge, overdischarge, short circuit test, etc. In order to test the performance of the battery, it is necessary to test it one by one according to the characteristics of the battery. The equipment use includes: lithium battery charge and discharge aging box, complete test machine, charger, etc.
When assembling 18650 lithium battery pack, you must follow the correct assembly steps to ensure safety and reliability in order to assemble a high-performance battery pack.