Homey Community Forum

Charge car with solar panels

The application [APP] Insight Trends was developed especially for the purpose of calculating trends and averages. This should be able to get the results you need without any trouble.

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Thank you very much for your answer! Unfortunately, to monitor the energy produced by solar panels to trigger an electric vehicle recharge, this formula is therefore not suitable.

Thank you very much, this is exactly the kind of application I was looking for! I haven’t figured out how to use it yet, but it’s clear that if I can get the average value over the last X minutes of an electricity production measurement by solar panels, that’s exactly what I need!

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Blockquote
(congratulations to the developer Homey of this app by the way!)

Thanks :wink:

I have some flows which combine the data from SolarEdge (amount of excess Solar Power (= export)) + Solcast forecast (my other app, which predicts the amount of Solar for my house)

But honestly, is there no option to link your charger directly to your inverter? (the Go-eChargers support Modbus data), This will avoid the use of Homey and sometimes unreliable flows (or flows which are disabled by themself)

(Same as OpenEVSE)

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Thank you very much for your suggestion (MODBUS).
I am not a IT specialist, so I don’t know if it is possible to link the two devices directly. I know Fronius is setting it up with a rebranded go-eCharger, but personally I have a SolarEdge and a go-e Charger HOMEfix (CM-03 version). Is it possible to link the two devices directly, or would it take a third party “Solar Manager style” device? The problem is that these third party devices cost several hundred euros, and if you make a serious calculation of profitability compared to the gains obtained by charging your vehicle with your solar panels, the profitability (return on investment) is almost impossible to obtain in a reasonable time (it depends a lot on the places and the different costs, but it is especially a calculation that many owners of these systems do not make or do not know how to make). Since I already have a Homey anyway, I’m trying to do it this way. This website could possibly be a solution as well.

This app is really working well, thank you a lot! With two flows, I get exactly what I want and it’s very flexible:

…and then:

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Glad to be able to point you in the right direction, but @MadMonkey deserves all the credit for thinking it up and making it reality.

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I really liked this example:

This helped me a lot setting this up for the exact same configuration, SolarEdge with E-Go charger.
This have to finish it, but getting the average from the last 5 minutes was something I was looking for.
Having this part working, pushing this number to the E-Go charger is easy.

What I want to do later is set up 3 profiles, Charge solar only, Charge ASAP and Night only.

Maybe I can do that in Homey, maybe in the E-Go app, lets see.

Hello everyone!

I would like to share with you the result I achieved in charging my electric vehicles with my solar panels, using Homey as a management box. I would like to remind you that this way of doing things allows you to save the purchase of a specific management device which usually costs between € 500.- and 1000.-, and which in most cases never pays for itself. The method presented here goes a little further than simply charging when there is enough sun, and stopping everything when there is not enough. The goal was to vary the charging amperage according to the available current!

Initial situation

  • a rather modest SolarEdge solar panel system (7 kW installed power), compatible with Homey
  • a go-eCharger HOMEfix wallbox, compatible with Homey
  • a 100% electric SKODA Enyaq that charges on a maximum of 3 phases / a 100% electric SKODA Citigo iV that charges on a maximum of 2 phases. Both vehicles are configured to accept maximum charging power. It is therefore the wallbox that manages the charging power, and not the vehicles
  • As my installation is rather modest and my two vehicles do not charge with the same number of phases, I decided to configure my wallbox so that it only charges on one phase. This allows me to charge with less power but almost all year round, without having to wait for sufficient sunlight. It also allows me to use the same flows for both vehicles
  • before starting, you have to note how much current the wallbox uses to charge, for 6 amps (A), 8, 10, 12, 14 and finally 16A (the maximum possible at my house). Here are the approximate values displayed by the wallbox for a single phase (these values will be used in the charge control flows):
    6A : 1.43 kWh
    8A : 1.9 kWh
    10A : 2.34 kWh
    12A : 2.78 kWh
    14A : 3.33 kWh
    16A : 3.78 kWh
  • the method presented here allows charging with solar power only. Another method that I developed initially allowed charging as soon as the cost of charging was equal to or less than the cost of charging at the low rate (i.e. at night at my home). However, I will not present this solution here, as it requires additional calculations to compare charging costs
  • I am not an engineer, nor an electrician, nor a computer scientist, so I did the best I could, but it can surely be improved. My electrical vocabulary is also very approximate (power, voltage, etc, I confuse everything…). The main thing for me: it works exactly as I want it to, transparently, and I understand how it works (unlike specific boxes where you don’t always know how they “think”)

Calculation flows

These flows allow to calculate, every 5 minutes (you can obviously choose to calculate more often or less often…), the average current that is injected back into the electrical network, and that is therefore available to recharge an electric vehicle. The consumption of the house is already deducted (about 250W when nothing special is running in the house). Furthermore, the value is also calculated so as not to take into account the current used by charging a vehicle. If this were the case, it would become too complicated for the charge control flows. My goal was to obtain positive values when current is drawn from the grid, and negative values when sufficient current is produced to be injected into the grid. The value calculated by the last flow is the only one that will be used in the control flows

Control flows

The two first flows presented here are used to activate and desactivate (with a shortcut or a physical button) the solar charge.

The control flows

A flow to stop the charge when not enough sun anymore

A flow to stop the charge when battery is full (or 80%…)

On this picture, you can see the result of a charge (in blue) carried out on Monday with a small voluntary break around 1.45 pm and a not very regular sunshine (in green). You can see that the blue curve follows the green curve relatively well. I am personally very happy with the result:

I remain at your disposal for any question, remark or proposal for improvement :wink:

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Great work!

I think you can reduce the control flows by calculating the required charging current so that you don’t need separate flows to set different values to charger. So one control flow would look like this.

When.
Insight Moy… variable has changed

And.
1p authorization… is true
Insight moy W is less than -1430

Then
Calculate
{{min(max(round(Insight moy W/230*-1,0),6),16)}} into variable “ChargingCurrent”

Set the the amperage of go-e charger to “ChargingCurrent” after 1s

I try to explain it further

  1. Calculate Insight moy W/230*-1 With this calculation you calculate the needed amperage value (positive value with multiplying by -1) for charging
  2. round(x,0) will round the value into integer because the go-e charger accepts only integer values
  3. max(y,6) will limit that the calculated value (ChargingCurrent) is never under 6A
  4. min(z,16) will limit that the calculated value (ChargingCurrent) is never over 16A

May need some tweaking but you get the idea.

If you want the control to be more accurate change your first calculation flow trigger from whenever solar power changes into trigger every 10s. This way you take also the consumption changes into account faster.

Also if you make the trend calculation for example every 1 min interval you could make the charging follow the curve more closely.

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Thank you very much for the good advice on simplifying control flows! I’ll try your proposal in parallel in a “safe” way, i.e. without direct influence on the wallbox but by modifying a simple Logic value to see if it works well :slight_smile:

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IS 6A the minimum the go-echarger?

If I do want to use most of the solarpower and like now shorter days, I get up to 5A.
Any idea if I could make (and how) to say something like if its more that 2A it should charge with 6A?
And when it goes above 6A, it should go to that amount?

Thanks to this post I was able to get the avergae in Watts and calculate Amps from that, AND I make it round up to a whole number, like 6A, not 5.86A.

Yes 6A on one phase is the minimum with the Go-e Charger (or I don’t know how to go lower). This corresponds to a charge of about 1’430 W per hour, which is really very slow. Personally, I’d rather charge at night at the low rate than less than 1’430 W. To charge an Enyaq to 100%, it would otherwise take several days.

Yes, makes sense, I am still not liking the idea of giving solar power back to the net, so even when its only 2A (500W) I am thinking to up it to 6A and still charge the car with 4A paid, 2A free.

Somehow I need to figure out to make it do this:
When 2A or higher, up it to 6A and charge car with this.
When above 6A just charge with that value.

The rest of the charging will be done at night, I can go up to 25A on 400V x 3 fases.

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