Controlling Tesla Gen 3 Wall Charger from RPI or API

[Per3110]

We have a model Y and mainly charge from our trailer using Solar, except for long road trips. I want to be able to control the Tesla Wall Charger so my batteries in the trailer is not drained too deep.

We have over 6 kW of Solar Panels on the trailer, 10 kW of inverter and 20 kWh of battery storage.

The main problem I have is the minimum charge level cannot be set lower than 50%. That means when I arrive home in the evening with 10%-15% can I not plug-in the car because it will charge more energy (40% * 80 kWh = 32 kWh, with no loses) than my batteries hold. If I need to drive in the morning for a short trip is the battery too low and I have to wait for the capacity from the battery in the trailer transfer to the car. With 40 Ampere is that almost 2 hours with 40 Ampere for the 16 kWh I want to use.
Anybody with a good idea to solve this?
I know I can just cut the power to the charger with a relay, but that seems like a bad solution with 40 ampere flowing. I rather have a nice software solution than gently stop the charging.

Another issue is the repeated charging during the night as the graph below shows.

Even when the car has reached the charging limit is it repeatedly draining the batteries in the trailer for a short time each hour. Again a control of the Tesla Gen 3 Wall Charger with a simple timer, RPI (Raspberry PI mini computer) or API can solve this too.

 

[archae86]

Have you considered using Scheduled Charging and on any given night setting the start time late enough that your charging rate won't deplete your source more than you wish by the time you intervene the next day?

 

[ucmndd]

Given your apparent sophistication and specialized needs, I’d look at a different and more customizable EVSE. OpenEVSE for example might be a much better fit than the wall connector.

 

[Per3110]

Have you considered using Scheduled Charging and on any given night setting the start time late enough that your charging rate won't deplete your source more than you wish by the time you intervene the next day?

That is a good idea. I try that next time i get to the RV with a low state of charge and need to leave next morning.

 

[Per3110]

Given your apparent sophistication and specialized needs, I’d look at a different and more customizable EVSE. OpenEVSE for example might be a much better fit than the wall connector.

Problem is i bought the wall charger already. But I take a look at it.

 

[Watts_Up]

Problem is i bought the wall charger already. But I take a look at it.

I built a very simple power switch to use excess solar energy to charge my EV or to run a water heatpump,
by detecting when my LiFePO4 battery cells are fully charged and also checking the solar energy produced
to avoid depleting my battery cells in case of cloudy day. It's very basic but sufficient enough.

 

[Per3110]

I built a very simple power switch to use excess solar energy to charge my EV or to run a water heatpump,
by detecting when my LiFePO4 battery cells are fully charged and also checking the solar energy produced
to avoid depleting my battery cells in case of cloudy day. It's very basic but sufficient enough.

I think that what I will do too. The charger recover fine if I flip the breaker off and later flip it back on again.

 

[ucmndd]

Problem is i bought the wall charger already. But I take a look at it.

I’ll buy it from you. $300.

 

[Watts_Up]

I think that what I will do too. The charger recover fine if I flip the breaker off and later flip it back on again.

Yes, depending of your location, you can just have a timer and a relay,
to charge your car or heat water from 11 am to 2 pm, except on cloudy days.

And the rest of the time, then you can charge your battery cells.
This was not optimum, but this just worked fine for me
between the spring and fall equinox,

However in winter months, I had only a third of the summer solar energy
and I barely had enough solar energy to charge my battery cells.
So no EV charging from solar then.

 

[Per3110]

Yes, depending of your location, you can just have a timer and a relay,
to charge your car or heat water from 11 am to 2 pm, except on cloudy days.

And the rest of the time, then you can charge your battery cells.
This was not optimum, but this just worked fine for me
between the spring and fall equinox,

However in winter months, I had only a third of the summer solar energy
and I barely had enough solar energy to charge my battery cells.
So no EV charging from solar then.

Yes there is a big difference summer, spring/fall and winter. We used to have 4500 watt of solar panels and travels north for the summer in the RV and ending in southern Arizona for the winter. Summer was more than 30 kWh, Spring/Fall 20 kWh and the shortest day in winter only 10 kWh. We now have 10400 Watt of solar panels so I expect those number to be 66/44/22 kWh. that still leave more than 12 kWh in the winter (on a sunny day). Last week we did 243 kWh with 170 kWh going to the Tesla. But we have a lot of clouds and thunderstorms in the afternoon here in the high mountains of Colorado.

 

[bradtem]

• You can resell your wall charger easily enough if you decide it's not right.
• In the Tesla app, you can now control both the charge level, current draw and charge times (including stop/start) of charging. You can also control all this via their API if you have the skill, or do scripts in TeslaFi. This does sadly require being connected to the internet. However, you don't need to do anything in your EVSE.
• Tesla wall connector gen 2 has an RS422 protocol to control them when they daisy chain. You can use that to tell the EVSE how much power to offer, and when. Just make your wall connector the 2nd in the daisy chain, not the first. This protocol is simple and has been reverse engineered.
• Wall connector gen 3 uses wifi and the protocol is not currently public.
• Many other EVSEs support a standard protocol for remote control, or have their own internal protocol.
• There are devices deliberately designed to control charging only when the solar panels are producing, if you want that.

Lots of options.