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Tesla BMS

48136 Views 107 Replies 23 Participants Last post by  Tomdb
As some of you might have been aware there has been some projects out there that have gotten the Tesla BMS slaves to work.

I have participated in a few. Currently I am working on getting software written to do all the basics like:
-Overvoltage monitoring
-Temperature monitoring
-Undervoltage monitoring
-Balancing during charge
-Current measurement
-AH counter

-Contactors/relays or other 12V signals
-PWM 'gas/fuel' gauge control
-Serial interface for Victron VE direct, a special request from Boekel.

The BMS controller/master is based around a teensy 3.2 and code is written in arduino. I will look at uploading my files to github so other can have a look and use it as inspiration.

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test setup to verify it works, a large resitive load bank.


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I was just at this moment looking at the github for this and logged on here to find the original discussion to learn more about it. I have not looked into a BMS system yet for my tesla batteries so probably have some newb questions.

My current understanding is i wire the BMS boards together and plug them into a arduino due or teensy 3.2. What i'm not sure is what happens from there.
How does the arduino tell the charger/ controller to start or stop.
how do these relate to a precharge resistor?

Thanks for your advice.
It's an exciting time in the Tesla BMS world :cool:

Damien is also making progress (here) and I look forward to all the shared battery greatness :D
Very interested in this:)
Itchyback: That is all done in software.

First iteration of this design will just do 12V signalling to turn on and off a charger. But got a canbus on the board for later use.

Remember use at your own risk.

Github has all my files, arduino code and schematics for the board


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Thanks Tom. Gonna build one of these.
test setup to verify it works, a large resitive load bank.
Terrific project you have there, thanks.

Anything written or a schematics for this large resistive load bank? What is the wattage and what are the resistors?
Here is a quick and dirty schematic.

It runs a Uno which reads a pot and changes the pwm duty cycle for the fet driver.

Mosfet is VS-FB190SA10
Used Driver is mcp1407

It will get a tempsensor on the heat sink so it does not overheat during testing.


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Good work, Tom. We have been able to source the connectors to attach to the Tesla board to build a wiring harness.

Have you thought about alarming wrt cell differential?
Here is a quick and dirty schematic.
Thanks Tomdb -- what is the maximum voltage and maximum current you may apply, and what kind of resistor is that and what is the approximate resistance?
On the load bank front, I need to add some capacitance on the input which is kind of logical, but i just forgot for some reason. :)

however knocked up two more boards for some beta testers.


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got some more testing done.

Proven out my bms will work and my load is stable so now to increase the power draw for higher current tests.
I have a few Tesla bms from the Rav4 ev (6cell) and at least one from the Smart car ev (15cell).
Is there any interest in taking a crack at those? You know, for science!
There are plenty of those out there as well.
If you mind posting them over I can take a crack. Or just some good pics of the boards would be a good start.

Or if you are software inclined and have an arduino due or Teensy give it a try yourself.
Here are those pics. I also have the pigtail for it as well.
I have a friend that is into arduino, ill have to see if i can get him to try.
As for shipping, I only now noticed you are in the UK. Ill see what i can do, no promises.


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RAV4 6s modules should work with the Telsa software/communication that is open source. As it uses the same layout as the Tesla model S.

Smart Car BMS looks different, what does the back side look like? It would be wierd if they would not use the Texas Instruments bms cell.
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