openinverter forum

Hello everyone,

I need some help, please. I'm trying to connect to a removed Model 3 battery pack (it's been taken out of the car) to check its specifications using an OBD2 (ELM) adapter.

I managed to connect using the "Scan My Tesla" app, but the app is displaying very limited data.

Could this be because the car was in an accident? Does the battery have some kind of pyrofuse or contactor that might have triggered? Is that why it's impossible to get all the data now?

There’s 2 can networks on the battery, have you tried the other bus?

No, I connected only one way.
+ and - are also connected to an external 12v battery.

jb23w wrote: ↑Tue Aug 26, 2025 9:16 pm No, I connected only one way.
+ and - are also connected to an external 12v battery.

The screw terminals near the connector need to be connected to ground

Connect both contacts to - ?
Sorry for the stupid questions

Those are the 12v posts out of the dcdc section of the pcs.

If the case is I modified then the grounds are fine. Try the charger port can

Unfortunately it didn't help. I connected additional contacts, tried to use a better quality ELM adapter. But the result remained the same.
Could this be because the car was crashed? Does the battery have some kind of pyrofuse or contactor that might have triggered?

The battery does indeed have a pyrofuse and it does indeed often blow in an accident. However, this does not stop the CAN communication at all. It still flows exactly the same either way. No, you're probably just using a crappy CAN adapter. I know, I know, you think you bought a good enough one. If it's an ELM device, you didn't. They are great for scanning for codes but they do not work fast enough to keep up with 2000 frames per second from the battery.

Use the pins labeled vehicle can. And use something better like an ESP32 board with CAN transceivers. Of course, if you do that, you won't be using Scan My Tesla. I have no knowledge of the app, maybe it normally gives you more battery info, I don't know. But, what I do know is that a properly working battery sprays out CAN messages like a firehose. It isn't picky about much of anything to start producing CAN. It's just picky if you want to actually close the internal contactors.

I have a battery basically completely disassembled, the whole top case off, nothing in the penthouse, and then the bms just sitting on top of the modules and that still works and provides all the CAN messages you could ever want.