Charging with "excess solar energy" (without Powerwall)

[israndy]

That's the way I was. I was begging on the Sense Forum and the TMC forum for people programming the Tesla Wall Connector with little boxes. Like 2 years, from the moment I put in my solar panels, which I also figured out how to install myself.

I finally gave up waiting for someone else to write code for me and I picked the right time to do it. The API, which is a programmer's interface for both Sense and for Teslas became available for free on GitHub, a place for programmers to dump their code so others can learn from it.

I already had Xcode installed on my Mac, so I downloaded the Tesla API and ran the three demo apps. Very cool. Then I spent an afternoon trying to isolate the code to make the car honk the horn. I wanted the smallest number of lines of code that would still do that. If I deleted too many lines I'd hit command-Z and get them back. Just changing, saving, running, and trying again. I finally figured out what the lines of code were that were important. I knew NOTHING about programming in Python and by the end of the week I could think of something that I wanted to do in Python and just write it. After a few more days I published my first UGLY code to GitHub because it ACTUALLY worked. It was pretty simple, read the solar and subtract the grid from it, that's the free solar, if that's in a range that the Tesla can charge in start the car charging, if not stop the car charging.

I have been working on it for about 4 months, basically every time I see an error I try to fix it and every time I realize something could be done more cleanly (I subscribed to a Python Hints email list) I re-code my app to use the new way of programming.

I got LOTS of help from the API owners (these guys reverse engineered the APIs the official apps use) to the point where the owner of an app called SenseLink wrote the code for my app to connect to his so I could read KASA plug in power monitors. So generous.

If you have the Enphase you could check if there is an API on GitHub.com for it and if you have a Mac install Xcode (free) and Python 3 (free) and see if you can download their demo apps. If you need hints or help understanding MY code I'm here for ya.

 

[holeydonut]

Yes my setup is basically how you describe there. I have ct's on the solar that feeds the panel so it can see the solar being produced then the main ct's that are before the main breaker can see how much is being sent to the grid. I'm not a programmer but it does not make sense to me why this is difficult for them to get working properly it should be a simple math equation that spits out a number to charge at but it just doesn't work. They also told me they tested with a Tesla but to me that is irrelevant since the charger sets the charge rate and car just takes what is supplied.

Hmmm yeah I wonder why it's not working. Your setup is literally their ideal use case. I thought maybe you had a solar install that was a line-side tap... and the Vue wasn't reading the export to the meter properly.

BTW, did you ever try to remove every CT from the Vue and see if it would work as just a simple in/out device to see what was going in/out of your load center main lugs?

 

[Tazzman]

Hmmm yeah I wonder why it's not working. Your setup is literally their ideal use case. I thought maybe you had a solar install that was a line-side tap... and the Vue wasn't reading the export to the meter properly.

BTW, did you ever try to remove every CT from the Vue and see if it would work as just a simple in/out device to see what was going in/out of your load center main lugs?

I have not tried changing anything since the people from Emporia can not offer any suggestions. I know when you change things in the configuration you lose all the data and I would not want that to happen.

 

[Tazzman]

That's the way I was. I was begging on the Sense Forum and the TMC forum for people programming the Tesla Wall Connector with little boxes. Like 2 years, from the moment I put in my solar panels, which I also figured out how to install myself.

I finally gave up waiting for someone else to write code for me and I picked the right time to do it. The API, which is a programmer's interface for both Sense and for Teslas became available for free on GitHub, a place for programmers to dump their code so others can learn from it.

I already had Xcode installed on my Mac, so I downloaded the Tesla API and ran the three demo apps. Very cool. Then I spent an afternoon trying to isolate the code to make the car honk the horn. I wanted the smallest number of lines of code that would still do that. If I deleted too many lines I'd hit command-Z and get them back. Just changing, saving, running, and trying again. I finally figured out what the lines of code were that were important. I knew NOTHING about programming in Python and by the end of the week I could think of something that I wanted to do in Python and just write it. After a few more days I published my first UGLY code to GitHub because it ACTUALLY worked. It was pretty simple, read the solar and subtract the grid from it, that's the free solar, if that's in a range that the Tesla can charge in start the car charging, if not stop the car charging.

I have been working on it for about 4 months, basically every time I see an error I try to fix it and every time I realize something could be done more cleanly (I subscribed to a Python Hints email list) I re-code my app to use the new way of programming.

I got LOTS of help from the API owners (these guys reverse engineered the APIs the official apps use) to the point where the owner of an app called SenseLink wrote the code for my app to connect to his so I could read KASA plug in power monitors. So generous.

If you have the Enphase you could check if there is an API on GitHub.com for it and if you have a Mac install Xcode (free) and Python 3 (free) and see if you can download their demo apps. If you need hints or help understanding MY code I'm here for ya.

I do not have Mac but I have tried playing around with Python and I know the commands to get the information from the Envoy on the local network I just have no clue how to put it together. Thanks for the information I just think it is beyond my skill level.

 

[Gwgan]

And once the EV is full, the solar has nowhere to go and hits the Grid. Resulting in NBC's

Please explain NBCs. Is this a per-kWh charge for adding to the grid? In ME on a TOU plan I have a fixed mnimum (~$12) + a consumption rate but no export charge.

ChargeHQ is discussed here Charge HQ Works great (had my first problem last night though).

 

[israndy]

Wow! Charge HQ seems great. Hope they build in support for my energy monitor

 

[holeydonut]

Please explain NBCs. Is this a per-kWh charge for adding to the grid? In ME on a TOU plan I have a fixed mnimum (~$12) + a consumption rate but no export charge.

ChargeHQ is discussed here Charge HQ Works great (had my first problem last night though).

I'm probably the wrong person to explain NBCs, because they're confusing as hell and I am not very smart. The easiest way I can get myself to understand California's NBCs is to effectively think of the NBC as a reduction in the value of solar export. I have no clue how NBCs could work in Maine.

So let's pretend you're a solar-customer on an annual NEM cycle... and you export 1 kWh at a retail rate of $0.30.

Without NBCs, if you took 1 kWh later at $0.30, that you'd net out since your export offset your import.

However, the NBC (in California) is basically $0.03 per kWh. So when you import your 1 kWh or $0.30 worth of electricity, you still have to pay $0.03 because a portion of your import has a non bypassable charge.

Where it gets inane is that someone could be thinking "HEY I exported $0.30 and got that credit. And then later I imported 1 kWh of which I could only apply $0.27 of my credit balance. That means I still have a $0.03 credit for later!". And this person would be wrong. The NEM person loses the $0.03 because they actually get a $0.30 value applied from their credit balance on the import. But then the utility slaps on a $0.03 fee that has to be paid with cash no matter what. so the solar customer conceptually spent $0.30 of credit to only get $0.27 of useful value. Blarg.

Anyway, if you charge your car with solar directly, you bypass the whole "export to the grid, then import from the grid later" malarkey. This means you've minimized your grid exports and imports. The utility cannot see what you're doing behind the meter (at least not yet), so they can't charge you NBCs on what you do in the confines of your house.

Of course, the CPUC is throwing out the idea that in the future, they require solar customers to install a consumption meter behind the normal PG&E meter. At which point they would see all the energy used at the house and they could charge a NBC on all consumption; not just what goes through the main meter. We hope that never happens. Fingers crossed.

 

[Gwgan]

Thanks, that was very clear. In ME delivery and supply are legislatively separate. The per-kWh billing is only on the net consumption. The utility managing delivery gets their “NBC” in the fixed base delivery fee plus a delivery rate above a threashold number of kWh. With net metering I never pay more than the base fee except sometimes a little in February when the credits have run out (they are only good for 12 months).
What is a typical NBC charge?

 

[israndy]

Those that got solar *after* NEM don't have to do the math, but our pay out is sucky, I pay 28 cents/kWh, but I get 7 cents for any power I send back to the grid. Let's just say I am motivated to use all the power I generate

 

[fikish]

OK I dunno I magically scoured around every answer but after 1-2hrs googling around, I can't honestly say I have an answer to whether the Tesla wall charger (3rd gen) allow solar-only charging.

I have solar and a powerwall and I just want to charger my ev using excess solar. I know chargehq works but my brain won't let up not knowing if latest Gen tesla wall connector does this natively. anyone?

 

[miimura]

OK I dunno I magically scoured around every answer but after 1-2hrs googling around, I can't honestly say I have an answer to whether the Tesla wall charger (3rd gen) allow solar-only charging.

I have solar and a powerwall and I just want to charger my ev using excess solar. I know chargehq works but my brain won't let up not knowing if latest Gen tesla wall connector does this natively. anyone?

There is no indication that Tesla Wall Connectors have any firmware to modulate the pilot signal to control the speed of vehicle charging based on external factors like solar production. In theory, it would be technically straight forward for Tesla to implement a system like this, especially for home networks that contain solar and Powerwalls, but there is no evidence that they have done it.

People have implemented a system to do this within the home (without something like ChargeHQ) by making a small computer like a Rasperry Pi act as a load sharing master for a Gen2 Wall Connector over RS-485 wired connection. In theory, you could do the same with a Gen3 WiFi Wall Connector by making the real wall connector think that the Power Sharing pool was being consumed by other Wall Connectors. However, I don't know of anyone who has reverse engineered the WiFi communications that the Wall Connectors use for this purpose.

 

[fikish]

There is no indication that Tesla Wall Connectors have any firmware to modulate the pilot signal to control the speed of vehicle charging based on external factors like solar production. In theory, it would be technically straight forward for Tesla to implement a system like this, especially for home networks that contain solar and Powerwalls, but there is no evidence that they have done it.

People have implemented a system to do this within the home (without something like ChargeHQ) by making a small computer like a Rasperry Pi act as a load sharing master for a Gen2 Wall Connector over RS-485 wired connection. In theory, you could do the same with a Gen3 WiFi Wall Connector by making the real wall connector think that the Power Sharing pool was being consumed by other Wall Connectors. However, I don't know of anyone who has reverse engineered the WiFi communications that the Wall Connectors use for this purpose.

OK thanks for that. confirmation for me they don't do this yet.

there's other chargers that do this. myenergi and zappi etc will utilize a "solar only" charging option which is what I'm looking for. just wanted to stay in the tesla hardware but alas. I could use charge hq tho

 

[miimura]

OK thanks for that. confirmation for me they don't do this yet.

there's other chargers that do this. myenergi and zappi etc will utilize a "solar only" charging option which is what I'm looking for. just wanted to stay in the tesla hardware but alas. I could use charge hq tho

I didn't notice your location before. I would recommend Zappi or ChargeHQ for an Australian owner.

 

[kHale]

I use my SolarEdge charger in solar-only mode. It adjusts to production/home usage pretty well. The big blue self-consumption periods are two separate charging sessions.

View attachment 810096

I have Solaredge system with a solarEdge EV charger, but we cannot figure out why the option to use excess solar is not showing up for us. Did you have an issues after you first installed the charger with using excess solar?

 

[DIRKULA]

I have SolarEdge EV charging and use the SolarEdge app to have excess solar only charge my MYP. The trick to using excess solar only is to have a 'scheduled time' for the car to charge in the SolarEdge app. I usually have it for 1 minute in the middle of the night, so it tricks the app into thinking it is charging outside of schedule and therefore using 'excess solar'. Excess solar is a fantastic feature, it will only use what is available or shut off until there is enough solar energy to charge EV. It will hug the production line, and not take any from the grid. see photos...