[BUG]Tesla Model S 75kWt external isolation - Deye 50kWt

[maxkav777]

Describe the error
Tesla Model S-X 2012+ External Insulation Problem - Deye 50kWt

Play
Tesla Model S 75Kwt 2018 Insulation Breakdown Problem when connected to deye 50kWt inverter after starting the contactors the external insulation starts to rise from 3300kΩ to the minimum threshold of 20kΩ, after which the contactors are disconnected

Expected Behavior
How to properly solve this problem?

Version and Settings

• Software Version: BE_v10.4.0_LilygoT-CAN485
• Battery Used: [Tesla Model S 75Kwt]
• Inverter Communication Protocol: CAN (Native)
• Equipment Used for Battery Emulator: LilyGo T-CAN485
• GPIO Controlled Contactors: [no]
• MQTT: [no]

[dalathegreat]

Sounds like you have an insulation leak. Check HV wiring, very common to accidentally crimp the shield wire into the HV connector. See the Wiki: https://github.com/dalathegreat/Battery-Emulator/wiki/Installation-guidelines#loss-of-isolation-zap

[maxkav777]

All wiring has been checked. Diagnostics show that with the contactors open, the internal insulation resistance is measured at 3.3 MΩ. After inverter startup and the beginning of charging, the insulation resistance drops from 1.2 MΩ to 20 kΩ. No issues are observed when the battery is physically disconnected from the inverter.

[dalathegreat]

Ouch, sounds like an internal battery issue then. Good luck with the troubleshooting!

[maxkav777]

Thank you for your response. I appreciate your time and it was a pleasure communicating with you.

[simonvetter]

After inverter startup and the beginning of charging, the insulation resistance drops from 1.2 MΩ to 20 kΩ.

What does the insulation value looks like with battery contactors closed but inverter stopped?

No issues are observed when the battery is physically disconnected from the inverter.

Disconnected at the inverter end, or at the battery HV connector end?

I haven't been able to find out the exact model of inverter you're using, but AFAIK Deye inverters are of "non-isolated" topology, meaning there is going to be an electrical path between the DC side and the AC side. As such, the insulation monitoring device inside the battery will detect that path and treat it as an insulation fault.
The inverter may also be performing its own insulation monitoring, in which case both IMDs (battery and inverter) would see each other as an insulation fault.

Has this setup ever worked before, or is it a new build?