Configure Tesla charger to automatically adjust to available solar power?

[Togg]

Ok, we're on our 2nd electric car, and I want to do it a bit smarter this time.

How might one configure a Tesla charger to automatically adjust it's amperage output to match our available solar power output at any given moment in time? For example, when the sun is bright I want full charging, but when we have half sun, I want the car charged at half the normal rate.

I noticed that in the Tesla HPWC (High Power Wall Connector) Installation Guide it shows how to set the operating current with dip switches, for a 40A, 60A, 70A, 80A, 90A, or 100A breaker. Is there a serial or digital input that can be used with this?

For our other electric car we have a Clipper Creek EVSE, and I can get an add-on board which allows power (amperage) delivered to the car to be turned full-on, full-off or several settings in between, i.e. no-power, full-power, or 1/2 power, etc. This is done either with what they call a 'digital' (not really digital) switch between some control wires, or via input from a serial link which I think is probably perferable.

Part of the reason we want this is because the electric company does not pay us much for extra generated electricity, so we would rather put it in the car. But at the same time, we don't want the car to charge at a fixed rate, because often our solar output is not enough, and during low sun times we end up buying electricity from the grid.

Any ideas on what might be the best (or any) solution to adjust the charging rate for the Tesla from information coming from either our solar production, or perhaps a small solar cell to simulate our solar production?

 

[juliusa]

If you have a newer Wall Connector, and not the old HPWC, there may be a way to do this with the signalling. Up to 4 wall connectors share a circuit and communicate with one-another do dial back the current when multiple connectors are in use. If you sniff the signalling between them, you could probably get your Wall Connector to believe there are other wall connectors in use and dial back the current.

I don't think the app has the ability to set charging current - that is only in the car. But it is possible it is visible in the API - if that is the case, then third party software could monitor your solar and control the charging rate from the car.

Finally, the best solution may simply be two clipper creek evse - easier to figure out that interface and just deal with that than trying to do both the clipper creek and wall connector.

 

[Argoniii]

There is a company in Europe that makes a charger that does this. Zappi Benelux - Home

 

[marksvend]

I set my car to charge at 20 amps starting at around 11:00 when production ramps up. That usually works as long as it's not too cloudy. It would be nice if Tesla added an API to adjust the charging amps so I could write a script to adjust it based on the solar production, which Solaredge monitoring has an API for.

 

[srs5694]

Part of the reason we want this is because the electric company does not pay us much for extra generated electricity, so we would rather put it in the car. But at the same time, we don't want the car to charge at a fixed rate, because often our solar output is not enough, and during low sun times we end up buying electricity from the grid.

How is the metering for this done? Are they measuring the excess power (on an instantaneous basis, moment-to-moment) and paying you for that over time, or are they aggregating your energy consumption and generation over a monthly billing period (either with net metering or some other system)? If the latter, then the timing of your charging doesn't matter to your bill, except maybe if you have the choice to delay one charging session from one billing period to the next. That is, if you use, say, 500kWh and generate 600kWh, it won't really matter if you used your 500kWh when the sun was shining or at night for billing purposes.

FWIW, here in Rhode Island, the solar plans are either net metering or a dual-meter system in which the consumption and generation are metered independently. Both of these measure energy over the course of a month-long billing period, not power generated instantaneously. There's also no time-of-use billing here in RI. I can conceive of systems being set up differently in which time of use relative to time of generation would matter, but I don't know much about non-RI solar installation billing, so I don't know what options you might have in California.

 

[EVDRVN]

Ok, we're on our 2nd electric car, and I want to do it a bit smarter this time.

How might one configure a Tesla charger to automatically adjust it's amperage output to match our available solar power output at any given moment in time? For example, when the sun is bright I want full charging, but when we have half sun, I want the car charged at half the normal rate.

I noticed that in the Tesla HPWC (High Power Wall Connector) Installation Guide it shows how to set the operating current with dip switches, for a 40A, 60A, 70A, 80A, 90A, or 100A breaker. Is there a serial or digital input that can be used with this?

For our other electric car we have a Clipper Creek EVSE, and I can get an add-on board which allows power (amperage) delivered to the car to be turned full-on, full-off or several settings in between, i.e. no-power, full-power, or 1/2 power, etc. This is done either with what they call a 'digital' (not really digital) switch between some control wires, or via input from a serial link which I think is probably perferable.

Part of the reason we want this is because the electric company does not pay us much for extra generated electricity, so we would rather put it in the car. But at the same time, we don't want the car to charge at a fixed rate, because often our solar output is not enough, and during low sun times we end up buying electricity from the grid.

Any ideas on what might be the best (or any) solution to adjust the charging rate for the Tesla from information coming from either our solar production, or perhaps a small solar cell to simulate our solar prduction?

Who is your utility and what rate plan? If you are on PGE E6 for instance this makes no sense. You should be producing at peak rate hours and using at low rate hours. What CA provider does not not do this where you need to draw at peak hours? Need some more info on your provider and plan as you may have better options.

 

[mswlogo]

There is a project that folks have decoded the protocol Tesla uses when using multiple Wall Connectors over RS-485. I think they are using a Rasberry PI to control amperage. The code is open source on GitHub. Sorry I don’t have links. But just google around or search this forum. This project is in progress.

If the Grid doesn’t pay you much for over production of solar you might consider a powerwall. They are expensive, but it should pay for itself eventually if the grid pays you so little for over production.

Most places either have off peak metering (great for EV) or net metering (great for solar). Not many places have both or neither. I have net metering with solar and grid pays me 80% of what I over produce. So a powerwall (which is 90% efficient) isn’t viable.

Without net metering (at a reasonable rate) or battery storage. It doesn’t make financial sense to even install solar. Rarely does your production match your load.

 

[DOCAL]

There is a project that folks have decoded the protocol Tesla uses when using multiple Wall Connectors over RS-485. I think they are using a Rasberry PI to control amperage. The code is open source on GitHub. Sorry I don’t have links. But just google around or search this forum. This project is in progress.

Not sure if this is the same stuff that @MITE46 does, but it certainly sounds similar.

 

[mswlogo]

Who is your utility and what rate plan? If you are on PGE E6 for instance this makes no sense. You should be producing at peak rate hours and using at low rate hours. What CA provider does not not do this where you need to draw at peak hours? Need some more info on your provider and plan as you may have better options.

I was thinking the same thing.

It is often optimal to send solar straight to your car battery (e.g. essentially making your EV a pseudo powerwall). But this should be icing on the cake.

 

[srs5694]

Without net metering (at a reasonable rate) or battery storage. It doesn’t make financial sense to even install solar. Rarely does your production match your load.

There is an alternative to net metering that's popular in Rhode Island. I don't know if it's got a formal generic name, but here it's called the Rhode Island Renewable Energy Growth (RE-Growth) program. It uses two meters, one for consumption and one for generation. Generated energy is bought by the utility at a much higher rate than consumed energy is bought by the consumer (~$0.32/kWh vs. ~$0.18/kWh, but I don't recall the precise figures). This is seemingly economically non-viable for the utility, but it's paid for in various ways, including the fact that solar power generation at least partially overlaps peak-rate times for utilities and the fact that individuals who sign on to the program sign a 15-year contract that locks in the purchase price for the energy, so the deal will likely become less favorable to consumers as time goes on. When I crunched the numbers, this plan beat RI's net metering plan for me unless I assumed near-hyperinflation levels of electricity cost increases. If the costs had been more similar, I'd have preferred net metering because it has a built-in protection against utility rate increases, but the RE Growth program was just much better, at least assuming no hyperinflation. I think I heard that similar plans are cropping up in other states, too.

 

[mswlogo]

There is an alternative to net metering that's popular in Rhode Island. I don't know if it's got a formal generic name, but here it's called the Rhode Island Renewable Energy Growth (RE-Growth) program. It uses two meters, one for consumption and one for generation. Generated energy is bought by the utility at a much higher rate than consumed energy is bought by the consumer (~$0.32/kWh vs. ~$0.18/kWh, but I don't recall the precise figures). This is seemingly economically non-viable for the utility, but it's paid for in various ways, including the fact that solar power generation at least partially overlaps peak-rate times for utilities and the fact that individuals who sign on to the program sign a 15-year contract that locks in the purchase price for the energy, so the deal will likely become less favorable to consumers as time goes on. When I crunched the numbers, this plan beat RI's net metering plan for me unless I assumed near-hyperinflation levels of electricity cost increases. If the costs had been more similar, I'd have preferred net metering because it has a built-in protection against utility rate increases, but the RE Growth program was just much better, at least assuming no hyperinflation. I think I heard that similar plans are cropping up in other states, too.

That sounds just like just plain old net metering. But at great rate. To incentivize people to invest in solar.

MA has a different incentive program called SRECS and also has a separate meter for all solar production. I basically get paid cash for 10 years based on what I produce. The cash I get is based on some bidding system and the rate varies each quarter. It essential made the ROI on installing solar around 6-7 years. So for 3-4 years I make a small profit. But as time goes on the checks get smaller. So the profit might not be all that much. That’s besides paying nothing for electricity.

The newer SREC program is not as generous as the one I’m on. Eventually it will be phased out. It was to help bootstrap the industry.

BTW thinking about it. That RE plan sounds like it would incentivize people to install a smaller solar system than they really should. Because they pay such a high rate for production (in kWh) that it could cover their kWh usage with a smaller system. Let's say they install a system some fraction based on that ratio $.18/$.32 of what they use. But they are paid (in kWh credits) at say $.32/$.18 so they target the net kWh they pay for to be $0 (also 0 kWh for the year) for a system that is way undersized. What else would they use the kWh credits for? Unless they are allowed to cash out those kWh credits?

The MA system actually incentivizes over sizing the Solar system. Because they only pay 80% on over production. So you have to produce a little more than you actually use to break even. Plus the SRECS pay based on what you produce, period. The bigger the system the more $$ you get. I'm sure they (electric company) wouldn't approve a system if it was too over sized.

 

[mswlogo]

I set my car to charge at 20 amps starting at around 11:00 when production ramps up. That usually works as long as it's not too cloudy. It would be nice if Tesla added an API to adjust the charging amps so I could write a script to adjust it based on the solar production, which Solaredge monitoring has an API for. View attachment 389910

That's cool. I didn't know solar edge had an open API.

 

[srs5694]

That sounds just like just plain old net metering. But at great rate. To incentivize people to invest in solar.

"Net metering" can mean different things in different markets. In Rhode Island:

• Net metering involves one meter that spins both forward and backward, with the solar panels installed behind the meter -- they're like a refrigerator that produces, rather than consumes, electricity. At the end of the billing period, the meter is read. If you used more energy than you produced, you're billed for the difference. If you produced more than you used, you're issued a credit for a (large) fraction of the difference. You can never turn the credits into cash, but they can build up and be carried over from month to month, so when you generate a lot of energy in the summer, the credits will reduce your bill in the winter. Under net metering, it's impossible to ever earn more than you pay for your electricity.
  
• In the RE Growth program, there are two meters. The one for your consumption works the way it always did and, assuming your energy use and the rate don't change, will result in a bill for the same amount as always (with adjustments). The solar meter measures your generation, which results in a payment that's split between a bill credit and a cash payment. In principle, the solar panels could be installed miles away from the house -- and for businesses that use this program, that could be the case. Under this system, there can be months when you'll receive a cash payment for more than your electric bill, and in theory you could earn more over a whole year than you pay. My own estimates for my system suggest I'll be paying the utility about $35/year more than they pay me, but that's a small enough difference that cutting back on my electricity use could make it go the other way.

In practice, both programs make it economically feasible to install solar panels. My installation isn't optimal (15 of my 17 panels face due west, the remaining two face south). I calculated an estimated payoff period of 8 years, which is on the long side. With net metering, it would have been longer -- 10 or 11 years, IIRC. They've only been installed since October, so I don't yet have a year's data with which to judge whether those estimates will be accurate.

MA has a different incentive program called SRECS and also has a separate meter for all solar production. I basically get paid cash for 10 years based on what I produce. The cash I get is based on some bidding system and the rate varies each quarter. It essential made the ROI on installing solar around 6-7 years. So for 3-4 years I make a small profit. But as time goes on the checks get smaller. So the profit might not be all that much. That’s besides paying nothing for electricity.

That sounds a lot like RI's RE Growth system. Are you sure the program name is SRECS? The acronym SREC generally means solar renewable energy credit, which is an accounting tool for green energy. Of course, Massachusetts may have given its program a similar name.

BTW thinking about it. That RE plan sounds like it would incentivize people install a smaller solar system than they really should. Because they pay such a high rate for production (in kWh) that it could cover their kWh usage with a smaller system. Let's say they install a system 2/3's of what they use. But they are paid (in kWh credits) at 3/2 (i.e. 150%) so the net kWh they pay for is around 0 for system that is 33% undersized.

Under RI's RE Growth program, you actually get paid in cash for part of the energy production. (The formula is complex.) As I said, you could theoretically earn more than you pay under that program, so there is an incentive to properly size it. National Grid wouldn't let me install as many panels as I originally wanted to, since their formula for what they permit is based on the system's theoretical optimum power output, not the annual energy generation. Since my installation isn't optimally oriented, that formula meant that I could only size it to about 80% of my annual consumption. Fortunately, I began leasing a Chevy Volt a couple years before installing the panels, so my solar installation is already sized for an EV. The Tesla I'm buying will probably increase that electricity use, but not by a lot. (2/3 of my Volt's miles are electric, and most of that remaining 1/3 are road-trip miles.)

 

[srs5694]

How might one configure a Tesla charger to automatically adjust it's amperage output to match our available solar power output at any given moment in time? For example, when the sun is bright I want full charging, but when we have half sun, I want the car charged at half the normal rate.

I don't know if it would help, but you might look into the Emotorwerks JuiceBox (or some other EVSEs that use their JuiceNet software; for instance, my Clipper Creek EVSE has the JuiceNet board installed) and the OpenEVSE project. Both of these EVSEs are designed to be network-controllable. The JuiceNet system can "talk" to some utilities so as to charge when the grid is providing cleaner electricity, but I don't know if there's any way to tie this in to your own solar installation. The OpenEVSE software is supposed to integrate with other home power appliances (including solar panels with some types of control software, IIRC), but I don't know the details of what it can do. These are probably both long shots, since they rely on integration with other products or services that you might or might not have, but they might be worth investigating.

Of course, you'll need to use Tesla's J1772 adapter with either of these products, since AFAIK they don't offer Tesla plugs.

 

[reddy]

Our area has a metering scenario similar to Togg. We have a bidirectional meter that measures consumption , and net production sent to the utility. I only get 'deferred fuel costs' credit for my production, which is about 2.4c per kWh.

I had previously asked here exactly the same thing , which is a way to adjust the charge rate of the car to the solar output.

Eventually, I purchased Tesla powerwalls, which allow me to time shift the use of the solar. Now I typically start charging when the Powerwalls are almost full, or in the morning when the sun is coming up and I still have significant remaining charge in the Powerwall batteries.

The price difference , and the tax credit, will offset the cost of the Powerwalls, but it's not a slam dunk in the economic use case.

We did have a major utility event here, after the 'bomb cyclone' 2 weeks ago, where our grid power was down for 31 hours. I not only had ample power for my home, but I was also able to charge my cars from solar while the grid was down. That's worth something....

It would be great if Tesla would add the ability to adjust the charging power from the app or API.

 

[buddhra]

wido/smarttwc

Here's a project that is using a raspberry pi to control a wall connector to follow solar output.

 

[dailo]

Here is a thread that discusses how to control this with the HPWC. I am hoping they will eventually allow changing the amps via the app so it can just be done over the API.

New Wall Connector load sharing protocol

 

[Moose408]

For me it was more cost effective to switch to the EV plan with PGE which only charges me $0.11/kWh overnight and just letting what little excess solar power I produced go back into the grid.

It wasn’t an easy calculation but once I had it it showed that the EV plan cost me a lot less.

 

[dailo]

For the PGE EV plan, it really only makes sense to charge with solar on the weekends during off peak rate to avoid the non by-passable charges, which most will probably determine is not worth the hassle. Does feel good to say you charged your car completely off solar though! PGE keeps changing its rate, the off peak rate is about $0.13/kWh now and if you are on NEM 2.0 you can't offset roughly $0.03/kWh.