What is IP67? How to reach IP67 for EV batteries?

The battery system of electric vehicles is a high-voltage electrical system. It is necessary to avoid foreign objects, ash, or water vapor entering the box during use, which will affect the battery insulation or other performance. In order to meet the requirements of all-weather use, the battery box must reach IP67. Here, the 6 refer to the dust-proof grade of the battery box should reach the level of “completely preventing foreign objects and dust from invading”, while the 7 here should reach the degree of “preventing water immersion when soaking”.

To reach IP67, it derived from design, manufacturing, and installation that each link needs to be carefully treated. Not only the box structure and sealing ring should be strictly controlled, but also the high and low voltage connections and wiring harness should be carefully designed and processed. The box of IP67 is almost completely sealed. To avoid damaging the sealing performance caused by the changes of spring, summer, autumn, and winter and different latitudes, a pressure balance valve with “air permeability and no water leakage” should be installed on the box.

To exactly reach IP67, Bonnen engineer would like to strengthen the below detail:

1) Three links of the connector or electric box sealing:

① the box base is sealed with the outer wall of the box. Pay attention to the seal ring and mounting hole installed on the base. When the installation hole is required to be blind hole design, the box should be designed with a blind hole. If the box is of thin plate structure and it is inconvenient to process the blind hole, the connector should be replaced or the sealing accessories with blind holes should be developed.

② The connector plug and socket must be inserted properly and matched well.

③ During the fabrication of the cable, it is necessary to ensure that the conductor is closely matched with it.

2) The small cavity inside the connector or MSD base is connected with the large cavity of the electric box, and the balance valve of the electric box is used to breathe together.

3) the “breathing” of the connector or internal cavity of MSD is conducive to long-term pressure balance and avoid damage. In addition, the “air cylinder effect” is reduced when inserting and plugging, which is easier to operate.
4) If the plug part is not operated properly, IP67 will be affected, so plug with complete wiring harness shall be inserted during airtightness test.

Other tips:
Box: there is no defect during manufacturing.
Balance valve: breathable without water leakage
Harness: there is no broken end of the wire

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