What is the insulation resistance standard for electric vehicles?

[GenevieveFitz]

Under the maximum working voltage, the insulation resistance Ry1 of the DC circuit should not be less than 100Ω/V, and the AC circuit should not be less than 500Ω/V. This refers to the current flowing through the surface layer of insulating materials in the system. The larger the value, the worse the insulation performance of the system. Hazards of electrical insulation failure: If electrical insulation fails in the system, it can lead to progressive consequences depending on the severity. A single point of insulation failure may not have an immediate noticeable impact on the system; however, multiple points of insulation failure can cause leakage current to flow between these points, accumulating heat in nearby materials, which may lead to a fire under certain conditions. Method of external resistance measurement: A series of resistors is connected between the positive and negative poles. By controlling the switches in the circuit, voltage values across the resistors can be obtained in two states. By setting up circuit state equations and solving them simultaneously, the resistance values from the positive and negative poles of the power battery to the ground can be determined, assessing the insulation condition of the battery poles relative to the ground.

[CharlieLee]

I just checked the information, the national standard for electric vehicle insulation resistance requires no less than 100Ω/V. For example, my 400V electric car has a minimum threshold of 40kΩ. However, this is just the safety baseline. When new cars leave the factory, they usually qualify only when reaching several tens of megaohms. The other day when I took my car for maintenance, the mechanic used a megohmmeter to test it, and it showed 120 megaohms. I always pay special attention to waterlogged sections when driving. After the heavy rain last time, a yellow warning light popped up on the dashboard, so I immediately went to the inspection station to check the insulation value. It turned out that water had seeped into the wiring harness connector at the wheel arch, and timely treatment prevented major trouble.

[DelJoseph]

In my years of repairing cars, measuring insulation resistance has been a routine task. According to the national standard GB 18384, the minimum requirement is 100 ohms per volt. When testing a 400V vehicle, if the megohmmeter reading falls below 40kΩ, it triggers a red alert. Recently, I worked on several flood-damaged vehicles. After opening the battery packs, I found that moisture had caused the insulation resistance to drop to 200kΩ, nearly triggering the power-off protection. Our workshop keeps hot air guns on hand to dry out the wiring harnesses. After treatment, the resistance can usually be restored to around 15 megohms.

[LaLydia]

According to the GB/T18384.3 standard, the insulation resistance requirement for our electric vehicle development is ≥ 100Ω/V. Taking a 400V platform as an example, the minimum design value is 40kΩ, while in the actual verification phase, we strictly control it to be above 100MΩ. During last year's three-high tests, we observed a 20% attenuation in insulation resistance under humid and hot conditions. Consequently, we added a double-layer silicone seal to the battery pack. On the production line, every vehicle undergoes a 2500V withstand voltage test to ensure compliance with insulation performance standards.

[LillianFitz]

The most concerning issue when evaluating a used car is insulation failure. According to the national standard of 100Ω/V, a 400V vehicle with an insulation value below 40kΩ is considered faulty. Last month, during an inspection of a three-year-old electric SUV, the diagnostic tool revealed that the battery-to-ground resistance had dropped to just 32kΩ. Further disassembly and inspection showed that the high-voltage wiring harness had worn out due to chassis scraping. After replacing the wiring harness, the insulation value was restored to 500MΩ. A reminder to everyone: always check the insulation data when purchasing a used car—avoid any vehicle with values below 500Ω/V.

[DiEmma]

While studying electric vehicle safety standards, I noticed that the minimum insulation resistance requirement is 100Ω/V. For a common 400V system, this means at least 40kΩ, equivalent to forty thousand ohms. New vehicles leaving the factory typically achieve over 50 megohms, which is a thousand times higher than the standard. During a visit to a battery factory, I observed them using saltwater spray tests to check insulation performance. Fellow drivers shouldn't ignore insulation warnings - my friend's car once had its resistance suddenly drop to 10kΩ during rainy charging, triggering the system to automatically cut off high-voltage power.