Polestar 2; Anyone communicate with BMS?

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Anamonta
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Polestar 2; Anyone communicate with BMS?

Post by Anamonta »

I am considering on buying a crashed Polestar 2 if the price is right. Plan is to use the battery packs in home ESS.

But I struggle to find anyone who have even taken apart the battery pack, or even more than that: Opened the communication with the BMS.

Any one here who could support me? Or link to better direction?
I would like to have some idea that it is possible to retrofit the batteries before I buy the car.

I have some experience with Atmels, Arduinos, ESP32, Raspi etc. But CAN is totally new for me. So I don't have any tools to read the CAN communication or understanding what to do with that.
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Re: Polestar 2; Anyone communicate with BMS?

Post by johu »

I don't know anything specific. This should be a good intro
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

I have a 69kWh Polestar battery (only modules, bms slaves, bus bars and cables, no case or contactors)
24 modules 2.88kWh 390mmx152mmx110mm 13.1kg, cell tap connector TE 936348-1.
8 BMS slave modules LTC6812 based (ISOSPI interface), connectors JAE MX77D040HF1 MX77A004HF2 MX77A004HF3
The bms slaves I have are populated with 14 balance resistors, the pcb is layed out for all 15 cells the LTC6812 supports.
Each BMS slave, monitors 3 battery modules (12 cells voltages, 6 temperatures). Each battery module has 2 NTC temperature sensors, Approx measurement 13k at 18degC, 17k at 12degC.

As I don't have any other Polestar parts I can't help with can bus decoding, In any case I think it would be easier to interface the BMS slave modules directly since the LTC6812 datasheet and code is available (Analog Devices Linduino)
For my vehicle conversion I intend to design my own hardware using LTC6820 to interface with the BMS slave modules with software based on simpbms.
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Anamonta
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Re: Polestar 2; Anyone communicate with BMS?

Post by Anamonta »

Good information johnlr!
My deal did not go thru. For my liking the asking price ended 4 000 euros too high. As it was whole car that had been in a side impact on read corner. So the whole rear was missing and also rear motor was ripped of the body.

But the BMS information is still interesting, as it seems the polestar batteries are quite well priced at the moment compared to capacity.
So please update your findings! I am very interested at the moment for your solution to utilize the battery.
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

I did find this:
https://www.ennoid.me/bms/gen-1
I don't know how suitable it would be for home ESS, it works with LTC6811 and LTC6813 slave modules so I expect it would work with Polestar LTC6812 slave modules. The hardware and firmware are open source, so it should be possible to make it work.
There is also what seems to be a copy of the hardware available https://maxkgo.com/products/maxkgo-bms- ... stem-mkbms
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Re: Polestar 2; Anyone communicate with BMS?

Post by m.art.y »

johnlr wrote: Fri Dec 01, 2023 12:49 pm I have a 69kWh Polestar battery
Hi, would you share what's the configuration? Is it known which cells are used? Thanks
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

m.art.y wrote: Sat Feb 10, 2024 9:58 pm Hi, would you share what's the configuration? Is it known which cells are used? Thanks
The modules are 4S3P, (3P was found online somewhere) 196.2Ah, either 24 or 27 modules per battery (69kWh or 78kWh). I don't know what type of cells are used, nominal voltage is 14.68V if that helps. I don't intend to open a module though, the cover is welded to the module frame. Picture of the label attached.
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Anamonta
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Re: Polestar 2; Anyone communicate with BMS?

Post by Anamonta »

Continue this thread. Someone seems to have opened the communication with 78kwh battery(BYD emulator releaced). But how about the smaller 69kwh, do we have any evidence the communication is the same?
Is it possible to swap these batteries? Car with 69kwh battery and change to 78kwh? At this time looking on buying 69kwh model without battery and install 78kwh battery to expand capacity.
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

Anamonta wrote: Mon Mar 11, 2024 11:36 am Continue this thread. Someone seems to have opened the communication with 78kwh battery(BYD emulator releaced). But how about the smaller 69kwh, do we have any evidence the communication is the same?
Is it possible to swap these batteries? Car with 69kwh battery and change to 78kwh? At this time looking on buying 69kwh model without battery and install 78kwh battery to expand capacity.
The 78kWh battery has 3 more battery modules and 1 more bms slave
69kWh 24 battery modules, 8 bms slaves
78kWh 27 battery modules, 9 bms slaves

To change a car from 69kWh to 78kWh will likely be much more difficult that just fitting the bigger battery. Communication at the isoSPI level (BMS controller to bms slaves) is the same but there 9 not 8 slaves. At the very least you would need the BMS controller from 78kWh (maybe that is the battery case, I don't know) or re-program the 69kWh one. Due to the higher battery voltage other controllers in the car (vcu, inverter, on board charger) would also need be replaced from a 78kWr car or re-programmed.
I think this would very difficult without the the support of Polestar.
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

I now have communication with the BMS slave modules (via isoSPI) working. I am using my own custom hardware (with LTC6820) and hacked Simpbms software. So far I can read all cell voltages (96 cells) and temperatures (48 2 per module).

Todo:
Calibrate battery temperature sensors. I need a thermal chamber to measure sensor resistance at 0, 25, 45degC, has anyone got access to one Hertfordshire/Essex border?

Test cell balancing turns the cell loads.
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Re: Polestar 2; Anyone communicate with BMS?

Post by johnlr »

A suggestion to produce a Polestar 2 bms solution.

ISOSPI Arduino shield DC2617A from Analog Devices, combined with UNO R4 (or some other controller) would make a nice CAN bus BMS, the only thing missing would be a 5V psu. This would provide full cell monitoring, balancing and temperature monitoring (subject to calibration), only 6 connections (power,can and ISOspi). I could provide working software based on my hacked version of simpbms.
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