Tesla BMS reverse engineering

[Pagode]

Hello collin80,

I am currently trying to connect Arduino Due with one Tesla Battery Package as part of a project for my study.
The Arduino is sending its messages but can't find the Tesla board.
I am also not sure how to wire the fault output you described in your hackaday project.
Hopefully you can give me any advice so that I can get further.

I am looking forward to hearing from you!

Reply:

Wiring:
red = 5V (Pin 1)
green = Ground (Pin 3)
yellow = TX (Pin 2)
white = RX (Pin 9)
black = fault (Pin 6)

[jorakarandas]

Hi Pagode, You shouldnt connect directly the boards to arduino due. Grab a 5v to 3.3v level shifter, like 74ahc1g08. Tell us your progress after that. Good luck, J

…

On Mon 30 Oct 2017 at 10:36 Pagode ***@***.***> wrote: Hello collin80, I am currently trying to connect Arduino Due with one Tesla Battery Package as part of a project for my study. The Arduino is sending its messages but can't find the Tesla board. I am also not sure how to wire the fault output you described in your hackaday project. Hopefully you can give me any advice so that I can get further. I am looking forward to hearing from you! Reply: [image: reply] <https://user-images.githubusercontent.com/33216693/32160508-55edf1c2-bd52-11e7-9d96-8587370158c2.JPG> Wiring: red = 5V (Pin 1) green = Ground (Pin 3) yellow = TX (Pin 2) white = RX (Pin 9) black = fault (Pin 6) [image: anhang1] <https://user-images.githubusercontent.com/33216693/32160475-3a78311e-bd52-11e7-95f1-d83e90e3ea03.jpg> [image: anhang4] <https://user-images.githubusercontent.com/33216693/32161399-acdc607e-bd55-11e7-854c-55299ae19391.jpg> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#5>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AREDHdpKoU7g_AEU-ra6mJVyoBdtTtVqks5sxYqDgaJpZM4QK1Ea> .

[danfador]

Hello, @Pagode do you succeeded with tesla BMS and Arduino, I have two model s module and I get an Arduino Due + Molex connector, what else I have to boy to comunicate with Tesla BMS?

One more question, without any external connection does testa BMS balance the cells ore not?

Thank you!

[bstarr119]

Good Evening All,

I am having similar troubles as the original poster, unfortunately I cannot upload pictures from the mobile site. I have incorporated a level shifter with the due so that I do not over volt the tx rx ports. I will need to figure out something new to try but I am running low on ideas as I am new to CANbus and due ^^

[NiallDarwin]

Hi @jorakarandas thanks for your suggestion of the level shifter. Please can you read this and let me know if I've understood correctly:
The ESP32 is a 3.3V chip & board so 5V could damage it.
The Tesla BMS boards are 5V.
This means that the Tesla board's Tx & Rx will be running at (up to) 5V and can therefore damage the ESP32. So using a level shifter means you can transmit the signal but drop voltage.
If all this is right I've got another question: Does the shifter cope with the baud rate OK? Is this a specification I need to look for when choosing a board?
Thank you :)

[collin80]

Yes, the Tesla hardware runs at 5V but an Arduino Due or an ESP32 run at 3.3v instead. So you need a level shifter to go back and forth between the two voltage levels. What you need is a level shifter that can go fast enough. You have the baud rate of the Tesla hardware (625000) so what you need is a level shifter that can handle 1MHz digital signals. Cheaper shifters probably won't. But, plenty of options exist. And, in a pinch perhaps you've already got AND logic chips. Just feed the input to both inputs to the AND gate and output at the proper voltage. Logic gate chips tend to be plenty fast enough. You just have to make sure that the chips you're using will trigger at 3.3 and 5v even if the inputs are technically higher in voltage than the V+ rail on the chip.

[NiallDarwin]

Thank you.

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On Thu, Aug 22, 2019 at 11:07 AM Collin Kidder ***@***.***> wrote: Yes, the Tesla hardware runs at 5V but an Arduino Due or an ESP32 run at 3.3v instead. So you need a level shifter to go back and forth between the two voltage levels. What you need is a level shifter that can go fast enough. You have the baud rate of the Tesla hardware (625000) so what you need is a level shifter that can handle 1MHz digital signals. Cheaper shifters probably won't. But, plenty of options exist. And, in a pinch perhaps you've already got AND logic chips. Just feed the input to both inputs to the AND gate and output at the proper voltage. Logic gate chips tend to be plenty fast enough. You just have to make sure that the chips you're using will trigger at 3.3 and 5v even if the inputs are technically higher in voltage than the V+ rail on the chip. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#5?email_source=notifications&email_token=AMIBEI2ON5TFNJWTDAN3D3DQFXDCDA5CNFSM4EBLKENKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD43MJRA#issuecomment-523683012>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AMIBEIYBLEFT67CK2NAGYJLQFXDCDANCNFSM4EBLKENA> .

-- Niall NZ cell +64 221 275 438

[NiallDarwin]

So I've now got bi-directional board very like this sparkfun offering and have made something happen. Unfortunately it seems I'm only transmitting not receiving-see screenshot. Two things I'm not sure of* are:
1/ I'm getting my 5V from the 5V pin of the Due. It's getting it from my laptop. My meter shows about 4.9V which I'd expect to be enough. Thoughts?
2/ Does the shifter need any pull up/down on any of the inputs or outputs?
If you want to see the rig, here's a little video.
Thanks :)

*Lots actually but these are the relevant ones ;)

[collin80]

1 -> Yes, 4.9 is sufficiently close. When dealing with USB you nearly never get a true 5V. It's almost always a bit less and it depends on the machine. Laptops tend to be the most lazy.

2 -> It shouldn't need any pull up or down resistors.

A few more pointers: Newer Tesla BMS boards actually communicate at weird higher baud rate. It's something like 632500 baud or something odd like that. It is only a tiny bit faster but tends to make newer boards function better. I remember them still working at the slower speed but you get a lot of errors. Also, the Tesla BMS slave board on the module has a blinky light that flashes when it is sending and receiving. As such, if your set up is working you should see the LED flash briefly every time you send traffic. If you don't then you aren't getting a proper signal through at the proper rate.

[collin80]

Just a correction. The slower, older speed is 612500, the newer speed is 631578. So the faster speed is only about 3% faster. But, 3% is a kind of critical zone for serial transmission and a 3% error is enough to make it work quite poorly. So, try both.

[BobbyBleacher]

Yes, the Tesla hardware runs at 5V but an Arduino Due or an ESP32 run at 3.3v instead. So you need a level shifter to go back and forth between the two voltage levels. What you need is a level shifter that can go fast enough.

Any recommendations? There seem to be an endless amount to choose from. I'm doing that same thing here as Niall (started hooking up my packs and inverter yesterday). Can't bring it all online and disconnect from the grid until I get all the monitoring online, though.

I bought the Due and the Teensy per the readme. Flashed the Due, but I'm guessing without the shifter in place I can't get any data to transfer because my serial monitor was completely blank.

[collin80]

One of the easiest things, and I think I said this above, is to just use a two input AND gate. Such a chip is here: https://www.mouser.com/Search/Refine?Keyword=74AHC1G08

It's a cheap trick. You provide your input to each chip at both input gates so that a positive signal on the gate turns it on. Then you power one gate with 3.3v for output to the Due or other 3.3v MCU and you provide 5v power to the other gate and use it to send to the Tesla BMS board. So, two AND gates, one inputs from the TeslaBMS and outputs to the Due, the other inputs from the Due and outputs to the BMS. These are then used as level shifters. AND gates are plenty fast for a sub-1MHz signal. In fact, the chip I linked to above switches in about 10ns so would probably work up to nearly 100MHz. That's sufficiently fast and the chips are pretty cheap too.

[wizkid057]

Was linked here by a friend. I haven't really followed this project, as I developed my own software/hardware to run the BMBs quite a while back (I actually just reflash the 8051 using Tesla's own update protocol, reverse engineered, and run my own code there.)

Anyway, the digital isolator used between the BMS side and the external connector can operate at 2.5V to 5.5V... and can essentially act as a level shifter on its own. Just power the external side from whatever voltage in that range would be useful to you. The filtering before the isolator is geared towards 5V operation, and this is the voltage Tesla uses for the bus... but definitely not a solid requirement. It'll give a few tenths of a volt loss most likely, but shouldn't drop things below the 2.5V minimum at 3.3V supply.

In fact, I'm actually currently running my own home setup with 36 of these in a chain, and it's running at 3.3V directly off of my board's 3.3V regulator (repurposed the board from another project... will eventually use 5V). Realtime view: https://wk057.solar/bms.php

All of that said, I'm unsure what the benefit of level shifter would be exactly, unless the 3.3V rail isn't strong enough to provide the few mA per board needed to run the isolators. You should just be able to power the whole thing from 3.3V and be done with it. The BMB won't know any differently, since the isolated side is still powered by 5V.

[collin80]

I'm sure you're right. We never investigated the situation that much. We saw that the Tesla main board uses 5v so we kept using that voltage and just added cheap AND gates to shift the signal level. But, it's good to know that this is not strictly necessary. So I suppose everyone else might as well just plain power it with 3.3v and be done.

[BobbyBleacher]

Well, Niall is getting more than me out of it. When I start up it tells me starting up and factory settings reset, but how do I actually retrieve any useful data now that I'm connected?

[BobbyBleacher]

Disregard, I've got this all connected, powered up, and operating.,The boards just aren't being recognized by the Due for some reason. I've tried the tx/rx pins as well as the cantx/rx with no success.