Why I'm here

[bwilson4web]

I have a home solar project in progress and this is one part:

• The battery hold panel energy for after sunset use.
• The Tesla Universal Charger has both NACS and J1772 plugs.
  • It can be tuned to charge my EVs in the middle of the day.

This is what my roof holds:

• 16 solar panels, 400 W
  • 3 facing SouthEast for morning sun
  • 13 facing SouthWest for mid-day and sunset solar
• Two large shade trees are now just ground down stumps

Bob Wilson

 

[insightman]

I have a home solar project in progress and this is one part:
View attachment 23828

• The battery hold panel energy for after sunset use.
• The Tesla Universal Charger has both NACS and J1772 plugs.
  • It can be tuned to charge my EVs in the middle of the day.

This is what my roof holds:
View attachment 23829

• 16 solar panels, 400 W
  • 3 facing SouthEast for morning sun
  • 13 facing SouthWest for mid-day and sunset solar
• Two large shade trees are now just ground down stumps

Bob Wilson

Thanks for the photos and the info. I'm looking forward to your tales of EVSE hacking to quantify the available current to your Tesla.

 

[bwilson4web]

There are three approaches

• Scheduled charging - least efficient, the EVs charge starting at about 8-9 AM at a rate equal to the solar panel production for the rest of the day until sunset. Since I have two EVs, switch each day. One variant is to use a daily profile curve so it approximates the solar production.
• Parallel solar - more efficient, I've ordered OpenEVSE boards to replace the abandoned JuiceBox 40 controllers and software. If I have source code access and schematics, I will add a small solar cell on a clip and cable as a sensor for the amount of sunlight the main group of Southwest facing arrays are receiving. Then modify the OpenEVSE software to use these measurements to adjust the charge rate. But it won't be sensitive to the smaller number of Southeast facing panels.
• Reverse engineer application interfaces of solar controller and Tesla L2 charger - the highest efficiency, reading the total solar production, set the Tesla and/or OpenEVSE chargers to match that for EV charging.

So this is why I am here. To share what I'm able to accomplish in tuning the solar array output to maximize EV charging without drawing grid power.

Bob Wilson

 

[andyG59]

Nice! We are in the process of a roof project ourselves and solar and eventual EVSE upgrade. I'm also interested in the project.

 

[bwilson4web]

I finally got my Tesla Universal Wall Connector up. My 2l4 GHz WiFi needed a repeater and everything is working. Bad news, it does not come with a builtin ability to adjust the output current limit.

What Tesla did is a $500 part added to their PowerWall:
https://energylibrary.tesla.com/doc...UID-993C3C77-5D23-4ACE-BF2C-2DB739D136DF.html

Beginning with Powerwall firmware 21.13, Tesla supports both the Neurio W1 (Tesla P/N 1112484-02-x) and Neurio W2 (Tesla P/N 1112484-04-x) meters and their accessories. While the meters serve the same applications, there are some differences between them which will be called out in the following sections. It is very important to note that Neurio W1 accessories are not compatible with the Neurio W2 meter, and Neurio W2 accessories are not compatible with the Neurio W1 meter.​

So no problem get one and reverse engineer it until "unobainium":
https://www.amazon.com/dp/B0CP8F2H24


I used to have some sympathy for the SuperCharger team that got fired. Not so much now.

I like the ability to charge either my Tesla or BMW i3 with the dual-plug, Tesla Universal Wall Connector. But not being able to adjust the output current 'built in', dam!

So I still have two options:

• OpenEVSE board - we'll see how open it is. This is an acceptable solution since L2 chargers will the co-located with my roof Solar Project.
• Spoofed "Control Pilot" - the charger uses a 1 kHz, +/- 12 V, pulse width modulated signal to tell the car what the maximum charge should be.

The Tesla Connector has freed up a Tesla J1772-to-NACS adapter:


I like this approach because I have all of the parts including a Raspberry Pi to build my own. Then offer piece parts for a reasonable price, 2x hardware, $70, plus labor, 3x hardware, $100 or roughly $140-170.

Requirements:

• User controlled, L2 charger amps
  • Solar flux sensor
  • WiFi monitor and control
• "Tickle the dragon" to avoid 120/240 VAC circuit over load - automate finding the circuit breaker "knee in the curve" to back off for an 'opportunity' circuit.

Bob Wilson