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ESS CAN Communication

Eguy

New Member
Jun 19, 2020
3
0
SG
Hii,

I'm from overseas but it seems like here some guys got quite deep into the systems of the Tesla Roadster.
Few words about me: I work as an electronics engineer in power electronics development. Therefore I'm very interested in electric cars, especially the Tesla Roadster. However I do not own an electric car (unfortunatly), but probably I get the chance of buying a Roadster with a damaged PEM, but working ESS.
I'd like to use this car as base for EV project.
I plan to exchange the inverter, onboard charger, motor and the 12 V DC/DC converter to water cooled components, additionally a new VCU and PDU will be integrated as well. Which means completely remove the PEM.
If successful this would end up at about 135 kW continous power and (depending on the battery's capabilities) up to 240 kW peak and 430 Nm peak torque at shaft. However, max. speed would be limited to 180 km/h (max. Motor speed).

Yes, I am aware, this is a big modification of this car and probably this is not just a "winter project", more a "multi-winter project".

My biggest problem is how to communicate to the ESS. How does it work? Communication over CAN. But CAN IDs,...? Is it possible to get the ESS running this way?
Does anybody ever tried something similar? Has anybody some knowledge about the CAN matrix of the Tesla roadster?
For such powerful traction system I need to get power prediction information of the ESS to limit inverter power to prevent overload condition of the battery system. How do I get access to this information?

Regarding charging, I've seen that there is a CHAdeMO kit. From my understanding, the ESS just accepts it if you "start charging" it, when the vehicle is turned on. Is that right?

Thanks, regards
 

X.l.r.8

Supporting Member
Feb 18, 2018
1,455
914
Toronto/Miami
Your first assumption is that the first EV used traditional rather than bespoke comms, the CAN is 3 systems rather than a can bus and its closed, you cannot hack into the system and its proprietary.
The PEM connects the the whole system so bypassing it means you have no drive. no charging, no communications and no communications. so you are buying a battery and a rolling chassis. The sensible suggestion is to make the existing components watercooled. that would make a huge difference because you won't have the problems associated with the fans and air filtration and burning pins. At the point you are at you may as well put a model 3 (toyota corolla of the EV world) system in the roadster, sells the known good ESS, they Gruber have the PEM and call it a day. thats a years worth of work right there. I know because I'm doing the same but with the LDU.
 

Eguy

New Member
Jun 19, 2020
3
0
SG
Is the BMS integrated into the PEM, as well? I think the BMS is integrated in the ESS, however I do not know how power prediction is done in this system.
The basic idea is to get a vehicle with integrated battery. Because the big issue about building an EV is to build a battery. Therefore it would be nice to buy a "rolling chassis with an integrated battery". But you need to get information about the current capabilities of the battery at different operating points.
Even if you put a model 3 system into the roadster, the issue about communication is still unsolved. I don't think a m3 system can communicate with a roadster ESS. At this point another option would be to remove the BMS of the ESS, so the ESS finaly becomes just a battery (without any intelligence), and of course attache a new BMS.
Furthermore, the model 3 system is using a proprietary communication, too.
I do not plan to make the existing components water cooled, I plan to exchange them to water cooled ones.

What's a LDU?
 

X.l.r.8

Supporting Member
Feb 18, 2018
1,455
914
Toronto/Miami
I wrote a long answer that even bored myself so I think the only course of action is talk to the original programming team, persuade them to ignore the non disclosure agreements they surely have and allow you to have full access to the electronic design and programming code.

The BMS controls the BMB’s that are situated in the ESS, those BMB’s could easily be substituted for any other design and controlled/read by a SIMP board. As the Tesla model S uses the same data they would be the obvious choice.
214DAA56-7CB3-4468-B5E1-B99493B655CA.jpeg


The LDU is the Large Drive Unit that the performance model S uses on the rear.
DA73B4BC-AF63-477C-A87B-E0153AF1D6A3.jpeg

as you can see the inverter is now next to the motor and is water cooled, as is the Charger,DC/DC inverter (I’m using the superior volt air cooled one) and battery pack.
 
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markwj

Moderator, Asia Pacific
Apr 10, 2011
4,604
1,219
Hong Kong
The CAN bus data specifications are not publicly available.

My concern would be that even if the ESS is ok today, it is likely to be 10 years old already, and liable to fail in the coming years. The sheets inside are not easily repaired, as everything is glued together, and the cells are not generally available.

If you had a Roadster glider (good body, but bad powertrain), then it would be more workable to look at putting a more modern powertrain in it (Tesla Model S, Model 3, etc).
 
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Eguy

New Member
Jun 19, 2020
3
0
SG
Hmm, well, so I don't know yet how old the battery actuall is. However compared to other components the battery is expensive and very time consuming to build. But I guess if the battery is in bad condition, there is no sense to go any further with the existing pack.
For BMS, probably the best is to exchange it to an open one. Everithing else seems not to be feasible.
 

markwj

Moderator, Asia Pacific
Apr 10, 2011
4,604
1,219
Hong Kong
The other components in the ESS housing (BMBs, Battery Safety Monitor, Auxiliary Power Supply, etc) are not complex to control. If you really did this project, shared engineering results that you discovered with the community, and demonstrated proficiency, I can guarantee that someone here would step forward and help you with the ESS CAN bus information you need to get it done. We've worked out most of this already anyway for the OVMS project.

That said, I still think the overall health and maintainability of the ESS in the car is still your biggest issue. Unless it is a 3.0 battery, the cells are about 10 years old. Even if it is a 3.0 battery, there are so few of those that spare sheets are hard to find (and with the 3.x replacement coming up it is unlikely there will ever be any more).
 

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