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Tesla BMS

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62K views 107 replies 23 participants last post by  Tomdb  
T
#1 · (Edited)
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

Outputs
-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.


https://www.youtube.com/watch?v=zmT5o5vDoH8

GITHUB

https://github.com/tomdebree/TeslaBMS
 
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#4 ·
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.
 
T
#7 · (Edited)
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.

https://github.com/tomdebree/TeslaBMS

Remember use at your own risk.

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

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#21 ·
I think this may be what you wanted.
The smart car was made in 2011, where as the Rav4 in 2014.
That could explain why the smart car bms is different and why the Rav4 is similar to the model s.
The rav4 also has 4 smaller 5 cell modules that have the same board but with one less row of balance resistors. Everything else looks the same.
 

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O
#25 ·
Hello,

I'm very interested. I live off-grid and my House Batteries are Tesla Mercedes B-Class Hybrid 7S Modules. I have three of them in parallel for about 9kWh (24v system). Been running these for about 2 years now and it would be nice to balance them.

The Slave BMS boards are on the modules, but I've left them disconnected. I would love to have them operational. Even if I had ONE of your controllers, I could switch it between my three modules just to balance the cells... although I believe they are functioning well, it would be nice for the long term.

I'm interested in learning Arduino but I have no experience. I'm handy... but again really a beginner with Arduino.

Are there any of these available? Or could you give me some very straight forward step-by-step??? It's really exciting what you're doing.

BTW for everyone watching this: For some reason the leads on my Tesla 7s modules (the wires running from the cell blocks to the BMS Board) have failed at the weld points. I was taking comparative measurement and they were all over the place. I thought... what??? Because the modules are working fine. Looking closer I found the balance wires to be loose at their weld points. So be sure to look into this and make sure your BMS leads are solid at their connecting points on the Cell Blocks.

Cheers!
 
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T
#28 · (Edited)
Currently running the pack attached to victron charger/inverter to cycle it.

Looks like she is balancing out pretty nicely.

As the pack is a 12S conversion, the temperature sensors are only on one of the two slaves. Need to remove Collins pack status or correct it so it does not fault out.

Okay so my pack overshot on the SOC calc, reason:
On boot up it uses a simple look up to roughly guess the SOC

4.2V is 100% 3.1V is 0%, so that lower value needs moving down. However the slave boards are keeping the cells nice and balanced during the charge of 35Amps and during the absorption phase allowing the slightly lower ones to catch up.
 

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#30 ·
Turns out I was just balancing with a inferior algorithm.

Balance cell if above balance setpoint.

This ofcourse wont do, should have changed it. But who looks at the full charge performance when there are other issues to address first.

Will become : Balance cell if above Lowest cell voltage.

Kevin, I got a sneaking suspicion it will talk very nicely. :rolleyes:
 
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