The continuous development of portable electronic equipment, electric tools, outdoor equipment and other fields battery higher requirements are put forward for its performance and durability. 18650 lithium battery is widely used in all kinds of equipment due to its high energy density, good stability and moderate volume. Especially when used outdoors or in humid environment, waterproof performance becomes an important consideration in battery pack design. This article will focus on the key links of customized waterproof 18650 lithium battery pack to help readers fully understand the technical points and technological elements that need to be paid attention to in the customization process.

I. Definition and application of waterproof 18650 lithium battery pack

18650 lithium battery pack is a lithium-ion battery monomer assembled by multiple 18650 models power system in series and parallel. Waterproof 18650 lithium battery pack on the basis of ordinary battery pack, focus on improving the sealing performance of the shell and the waterproof level of the overall structure to ensure that the battery pack works safely and stably in rain, moisture and even short-term immersion environment.

Waterproof lithium battery pack is widely used in outdoor lighting, electric bicycles, unmanned aerial vehicles, medical equipment and other scenarios requiring waterproof protection. Its design needs to take into account battery performance, safety and waterproof performance.

II. Design points of customized waterproof 18650 lithium battery pack

1. Cell select and match

the performance Foundation of waterproof 18650 lithium battery pack comes from high quality cell. 18650 cell with high capacity, high rate discharge and good cycle life should be selected for customization. Cell strict screening and matching are required to ensure the consistency of voltage, resistance and capacity of each monomer in the group, so as to avoid overall performance degradation or potential safety hazards caused by uneven monomer.

2. Structure design of battery pack

the structural design of the waterproof battery pack needs to take into account the tightness and heat dispersion:

• sealing structure design
  the Shell should be made of high-strength and corrosion-resistant materials, such as aluminum alloy or engineering plastics, and be waterproof and sealed through reasonable structural design. Common methods include sealing rubber ring (such as silicone ring), waterproof tape, and glue injection technology to ensure that there is no potential leakage at the joint.

• Heat dissipation design
  although the sealed structure is effective and waterproof, it is easy to cause heat accumulation inside the battery pack. Therefore, it is necessary to design a reasonable heat dissipation path and use thermal conductive adhesive or cooling fin to assist in heat dissipation, so as to avoid affecting battery performance and life due to high temperature.

3. Waterproof grade standard

custom Waterproof 18650When lithium battery pack, it is necessary to specify the waterproof level requirements. Common protection levels such as IP65 and IP67 are as follows:

• IP65 indicates that the battery pack can prevent the injected water from invading.
• IP67 it means that the battery pack can be immersed in a certain depth of water for a short time without water entering.

Select the appropriate waterproof grade according to the actual use environment, and design the sealing scheme and testing process accordingly.

4. Electrical protection design

in order to ensure safe and reliable operation of waterproof battery pack, perfect electrical protection measures should be integrated during design:

• battery Management System (BMS)
  BMS is responsible for monitoring parameters such as voltage, current and temperature of battery pack to prevent abnormal conditions such as overcharge, overdischarge, overcurrent and overtemperature. When customizing, BMS should have high reliability, and its installation location should also consider waterproof treatment.

• Connector and line waterproof
  waterproof measures shall be taken for input-output interface, connecting wires and welding spots of the battery pack. Common methods include using waterproof connectors and sealing glue to seal circuit parts to avoid short circuit or corrosion caused by moisture intrusion.

3. Customized waterproof 18650 lithium battery pack process

1. Cell screening and Pretreatment

firstly, the capacity, internal resistance, open circuit voltage and other indicators of the purchased 18650 cell are tested, and unqualified cell are eliminated. Match qualified cell to ensure balanced performance cell within the group. At the same time, clean the surface of cell to avoid dust and oil pollution affecting subsequent processes.

2. Assembly and welding

according to the designed series-parallel connection scheme, the cell is welded into modules with nickel tape. The welding process should ensure that the welding spot is firm and the heat affected zone is properly controlled to avoid damage to cell. After welding is completed, conduct electrical performance testing to ensure correct connection and no abnormality.

3. Insulation and protection treatment

wrap the battery module insulation material to prevent short circuit. According to the waterproof design requirements, install sealing ring or coating waterproof adhesive at the joint to ensure that the assembled whole structure has no risk of water leakage.

4. Shell assembly and sealing

install the battery module into the designed waterproof shell, install sealing washer, and fix it with screws or buckles. The interface of the shell is sealed twice to improve the waterproof level.

5. Testing and verification

after assembly, conduct waterproof test and electrical performance test:

• waterproof test
  according to the waterproof grade standard, conduct spray test or immersion test to confirm that no water enters the battery pack.

• Function test
  carry out capacity test, internal resistance test and discharge test on the battery pack to verify that its electrical performance meets the design requirements.

• Security test
  including short circuit, overcharge, overdischarge and other safety performance tests to ensure safe and reliable operation of the battery pack.

IV. Precautions for customizing waterproof 18650 lithium battery pack

1. material Selection
   the sealing material must be resistant to aging, high and low temperature, non-toxic and environmentally friendly, so as to avoid sealing failure caused by material performance degradation.

2. Process control
   the sealing process has a great influence on the waterproof effect, and the operation needs to be standardized to avoid problems such as uneven coating of sealant and inadequate installation of sealing ring.

3. Environmental adaptability
   during customization, the temperature, humidity, vibration and other factors of the battery pack in the actual use environment should be considered to ensure that the structural design and material selection can meet a variety of complex working conditions.

4. Regulations and certification
   waterproof lithium battery pack shall comply with relevant safety and environmental regulations, such as UN38.3 Transportation certification, CE certification, etc., to ensure that the products enter the market legally and legally.