Has anybody worked out the wall charger communication protocol yet?

[IanAber]

I charge my Model S entirely from Solar power in an off grid location. When the sun goes behind a cloud I need to adjust the charge rate down a bit so I don't flatten the house battery. To do this I need to talk to the wall charger to tell it how much it can have dynamically. I am 99.9% certain that the communication protocol by which multiple chargers can coexist and share a common 100A feed will allow me to do this but Tesla will not release the details to me. I could reverse engineer it if I had two chargers and two cars but I only have one of each so it is extremely difficult.

Has anyone out there done this already and would you be willing to share your findings with me?

Any other ideas would also be gratefully received.

 

[BigD0g]

I think maybe @wk057 ? He was talking about putting a DC charger like super charger in his garage at one point.

 

[daxz]

Could you use the car's web services and have the car temporarily turn off charging? Tesla Model S JSON API · Apiary

 

[IanAber]

I can turn it off, this is true. The problem is that when the sun is not shining fully on the solar panels I still get a lot of power available, just not enough to charge at the maximum rate. If I only allowed it to charge when there is full sun I would lose a lot of charge time. If I set the car to a lower current then I cannot make full use of the full sun.
I know this is possible given the capabilities of the hardware, I just need a little documentation.

 

[Acho]

This may help a bit

New Wall Connector load sharing protocol

 

[brkaus]

Yes, there is a thread has lots of hints and some code. Let me find it.

Oops - @Acho already posted it. Thanks!

 

[gork]

GitHub - cdragon/TWCManager: Control power delivered by a Tesla Wall Charger using two wires screwed into its RS-485 terminals.

This is a small application which runs on Linux (like a Raspberry Pi w/ USB<->RS485 adapter) that simulates a master TWC to control up to 3 TWCs in slave mode. I do not believe it can directly read the SOC from connected cars, but it can read the current consumption and set current limits on each slave TWC.

 

[IanAber]

Thanks gork and acho for the links. This looks to be exactly what I need. I will report back on my experiences when I have had a chance to check it out.

 

[IanAber]

As an update, many thanks to CDalton for this excellent work. I installed the software on a Raspberry Pi and wrote the necessary code to sit between my battery management system and the TWC Manager to control the charging rate. I have one Model S and I can now leave it to its own devices to charge with the TWC Manager controlled by my own code adjusting the charge rate based on a combination of house battery charge level and available solar power. Hopefully, I will not be in a position of having the car flatten the house battery again!

 

[RScottyL]

As an update, many thanks to CDalton for this excellent work. I installed the software on a Raspberry Pi and wrote the necessary code to sit between my battery management system and the TWC Manager to control the charging rate. I have one Model S and I can now leave it to its own devices to charge with the TWC Manager controlled by my own code adjusting the charge rate based on a combination of house battery charge level and available solar power. Hopefully, I will not be in a position of having the car flatten the house battery again!

One of the great things I have always loved about forums.

You have people that are very helpful by sharing knowledge and information for a common cause, which in our case is Tesla!

You learn things and figure out things that the manufacturer doesn't share!

 

[jaguar36]

Would be awesome if you could share the work that you have done as well!