Matters needing attention in the cell composition of the battery pack: including cell screening, aluminum-plastic composite film, top sealing (edge sealing at the end of the pole), side sealing, protection of the pole, and measures to prevent mechanical impact and short circuit.
1. The problem of battery screening, how to distinguish between good and bad after the battery is in hand. Must use internal resistance tester and capacity tester. Test the nominal MH, and the actual MH. If the distance from the nominal parameter is larger, the quality is worse. The lower the internal resistance of the battery, the better. The battery core is a pit, check and test if you have equipment, buy lottery tickets if you don’t have equipment
2. Aluminum-plastic composite film outer packaging protection: It is important to prevent being damaged by sharp parts. For this reason, the environment around the battery should be cleaned up from time to time, sharp parts are prohibited from contacting or hitting the battery cell, and gloves can be worn when taking it to prevent the surface of the battery cell from being scratched by the fingernail.
3. Top sealing and side sealing protection: in order to prevent the top sealing and side sealing from being damaged and destroying the sealing effect, it is forbidden to bend the top sealing and side sealing; at the same time, the cell design must adopt reliable insulation isolation Measures to prevent short-circuiting of the negative electrode and the aluminum-plastic composite film.
4. Pole handle protection: The positive lead terminal of the polymer lithium ion battery cell adopts an aluminum pole handle, and the negative lead terminal uses a nickel pole handle. Because the pole handle is thin, bending should be prohibited; at the same time, the pole handle should be prevented from contacting with the aluminum-plastic composite film during the production process, and the ferrule film should be strictly isolated.
5. Insulation protection: In order to prevent battery polarity short circuit when assembling multiple single cells in series, it is necessary to conduct insulation treatment. Use PC film or silicone film to separate the battery tabs and then wrap multiple layers of insulation. Tape to fix it, and then add an insulating layer to the position of the welding wire, and then add striped glue to fix it.
6. Prevent mechanical impact, such as falling, hitting, bending the battery cell and accidentally trampling on the battery.
7. It is forbidden to short-circuit the positive and negative electrodes with metal objects or wires.
8. Waterproof protection: Lithium-ion battery is assembled, and then packed with insulating glue. Or choose a waterproof battery box.
9. The battery pack is required to be shockproof! Electric vehicles cannot be used as off-road vehicles in use! The outer skin of the battery pack can't be used to buffer the collision. Deformation will cause a short circuit! Try to use the grille bracket + cushion + outer box. Without the grille bracket, the battery pack will cause the nickel sheet to fall off under the squeeze of years of activity!
10. Do a good job of heat dissipation, and use a thermal conductive silicone grease pad as a medium to guide the heat to the stainless steel housing. Or the battery pack is conditionally supplied with heat conduction channels, and during energy conversion, timely heat conduction can optimize the battery. Steel outer box + fan assist are conventional solutions.
11. Anti-corrosion problem. The battery will rust after being left for a long time. If possible, take anti-corrosion measures as much as possible.
After a battery cell is completed, the next step is to correctly combine the shell and the battery cell protection circuit module to make it a polymer battery. The precautions in this process are as follows:
1. Shell design:
(1) Sufficient mechanical strength to prevent the battery core from mechanical damage by external force,
(2) When the battery core is installed in the shell, prevent the sharp corners of the shell from scratching the battery core;
(3) Prevent short circuit caused by contact between the pure aluminum of the aluminum-plastic composite film and the outside.
2. The battery cell protection circuit must be designed: including the scientific setting of the highest/lowest voltage, over-current protection, the battery unit (single cell) needs to be protected from overcharge and over-discharge when the battery is used in combination.
3. The transfer of the positive aluminum pole handle through the nickel strip and the connection between the battery cell and the circuit board should be performed by ultrasonic welding or spot welding.
4. Reliable positioning of the battery cell. After the battery cell is assembled, it should be fastened firmly in the housing without loosening at will, so that the entire lithium-ion battery structure is in a consolidated state.
