How to Build an Intelligent Car Charging Logic with?Loxone

You can build an individual charging logic that matches your mobility pattern without much?effort.

Are electric vehicles (EVs) still a good thing, given energy prices soar to unprecedented levels and we risk running into an energy scarcity situation the next winter?

Yes, of course, they are.

But only if you can charge your EV with renewable electricity, preferably from your own roof at home or work.

Easy, right?

Not really. Your car needs to be parked and plugged in at the time when the sun is shining. Plus, because solar energy varies with the clouds and over the day, you’ll need to spend lots of time and attention on managing the charging of your car.

The good news? There is a solution to this problem, which can easily be adapted to match your mobility patterns and your lifestyle.

The solution is called a building control system. In this article, I will take you through the intelligent car charging logic I built using Loxone. This building control system is relatively easy to use, yet still flexible enough to implement a variety of functions.

Before we start, let me be transparent: I am an electrical engineer by training, and the rest of this article will be quite technical.

What is?Loxone?

Loxone is an affordable off-the-shelf building control system. In my view, its key advantage is its modular design with a miniserver at its core. The miniserver is installed directly in your house, and logic can be configured and uploaded directly to the miniserver. Furthermore, a wide range of building automation components is supported; ranging from electric car charging stations to lighting products to media servers.

On the downside, the configuration is somehow clumsy and error-prone. But given the fact that configuration is a one-off effort and the advantages of Loxone are recurring, I’m happy to accept the downside.

The Setup

The overall energy setup of my house is described in a separate article:

Solar Self-Sufficiency Is Feasible, Even in Moderate Climates

The same thing is true for the basics of charging patterns, especially in the dark winter months:

Solar Self-Sufficiency: Optimizing Winter Car Charging Patterns for Geopolitics

My Loxone setup for car charging is as follows:

• Loxone miniserver (2017 model)
• Keba KeConnect p20 charging station (2017 model)
• Keba KeConnect p30 charging station (2019 model)

All components are connected through wired Ethernet, allowing stable connections and minimal latencies.

The Logic

Now for the fun part. I will describe my Loxone logic in detail.

Charging Mode

As a first step, the logic distinguishes between summer mode and winter mode:

• “Summer Mode”: Between 15th February and 31st October, charge whichever car is connected during times when there is at least 3.5kW solar power excess production.
• “Winter Mode”: Between 1st November and 14th February, charge all connected cars between 10 am and 3 pm, when solar power is strongest, using the maximum charging power of 12kW.

As described in a previous article, I have optimized the summer and winter modes over time, adapting both to our needs and to geopolitical shifts.

Charging Station?Selector

Since we have two electric cars and cannot charge both cars simultaneously on 12kW each due to the limitations of our solar installation, a selector defines the charging priorities if both cars are connected:

• The car of my wife always has charging priority, since she uses it to commute to work and I commute by train.
• My car is only charged once the charging of my wife’s car is complete, or it is disconnected. If my car charges and my wife’s car docks, charging on my car is stopped and started on my wife’s car.

Of course, the charging priorities can be overridden manually using the Loxone app.

Charging Current

To maximize self-sufficiency (and hence minimize energy costs), controlling the charging current is at the heart of my car charging logic. It takes into account available excess solar power, and the charge state of the house battery, and is even able to bridge short cloudy periods on variable days.

The charging current is set on a very simple feedback loop, where the charging current is compared to the available excess solar power.

Flexibilities

The logic I described above is mirroring just our mobility pattern and does not represent a generic solution.

However, Loxone features many elements to adapt a generic solution for individual needs. For myself, I used triggers and timers to make sure the charging logic works without any manual intervention.

Limitations

As mentioned in the introduction, the Loxone configuration software is somewhat clumsy. Here are the largest limitations to be aware of:

• On some elements, Loxone uses the units of watts. On some other elements, kilowatts are used (see the textboxes in the screenshots above). It took me ages to find out…
• Testing a car charging logic that depends on variable solar power is not straightforward in Loxone, as there is no way to simulate time series of individual parameters.
• My charging stations can only charge on 3 phases. Modern models can switch between 1-phase and 3-phase charging. Switching to such charging stations would greatly increase self-sufficiency in the winter months.

The Results

Using the charging logic described above, here are some typical summer mode charging patterns:

And here are some winter mode charging patterns:

Conclusion

Having the ability to control the charging logic for your electric cars is an asset both in financial and in self-sufficiency terms. Yet there are no generic solutions, as mobility patterns and individual needs vary widely.

If you’d like to use my logic as a starting point for your solution, post your email address in the comments section and I will send you the Loxone config file by email.

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