Wiring harness assembly and air tightness test in battery pack

Wiring harness assembly and air tightness test in battery pack

The wiring harnesses in the Pack are generally divided into low-voltage wiring harnesses and high-voltage wiring harnesses. Low-voltage wiring harnesses refer to wiring harnesses such as voltage sampling wires, temperature sampling wires, communication wires, and control wires; high-voltage wiring harnesses mainly refer to main loop wiring harnesses with excessive current, such as copper bars and connecting cables. There are generally two ways of wiring harness connection, one is the plug-in method, and the other is the bolt fastening method. In practice, how to choose depends on the needs of customers and products.

The correctness of the low-voltage wiring harness must be fully checked before installation, otherwise the wrong wiring or insertion of the wrong wiring will cause a short circuit and cause serious consequences. Generally, manufacturers will make test tooling to detect, so that the operation is convenient, the efficiency is high, and there is no error.

Before connecting the high-voltage wiring harness, you need to check the documents and memorize the connection sequence. When conditions permit, it is best to make fool-proof tooling to avoid short circuit of the electric box caused by misoperation of employees, which can lead to product damage and serious casualties.

There must be no idea of ​​trial and error in the wiring harness connection, because the batteries are all charged and need to be 100% confirmed before they can be connected; if the connection is wrong, it may cause serious consequences, as long as you always keep the safety at ease and keep it at all times With a sense of crisis, dangerous events will not happen easily.

The air tightness test is a safety test, and it is generally required to reach the IP67 level. At present, there are three methods for testing air tightness in the industry: positive pressure test, negative pressure test and flow test. How to choose in practice, comprehensively evaluate according to your own situation, and follow the principle of not lower than customer standards and national standards. The following mainly introduces the matters needing attention from the perspective of assembly.

(1) The installation of the box connector.
Generally, the Pack system will have safety valves, MSD protection switches, low-voltage wiring harness connectors, and charging and discharging connectors. When installing these devices, pay attention to the matching and sealing of the box. If the matching and sealing are not good, it will cause the box to be sealed. If it fails, the IP67 test fails.

(2) Installation of box cover and box body.
The sealing of the box body and the box cover is generally completed with the help of a sealing strip or sealant, and also depends on the shape and complexity of the box body and the box cover. When installing, be careful not to damage the sealing strip. If it is a sealant, you need to wait for the glue to solidify before installing. The box body and the box cover are fastened, usually by tightening the screws to compress the sealing strip, so that the sealing strip produces reasonable compression and deformation, so as to achieve a good sealing effect.

(3) Air tightness test.
The air-tightness of the test box generally needs to be carried out by a special test instrument, and at the same time, the sealed connection with the tested box needs to be considered. If a positive pressure test is used, the testing process is divided into four stages: inflation, pressure holding, testing and exhaust. If the tested box has poor sealing performance, the holding pressure value may not be reached, and the leaks need to be checked and repaired again. test.

In the actual test, you need to pay attention to checking the leak-prone points, such as the seal of the connector, the seal of the safety valve, etc.; at the same time, the pressure should not be too high during inflation, preferably not more than 0.3MPa. If a leak is found during the test, and it is not easy to find the leak, it is recommended to use soapy water, and apply soapy water to the place that is considered to be easy to leak until the leak is found. After the leak check is processed, repeat the test. If it fails, continue to search until it passes.