TL;DR
Want to install a power plug with dynamic maximum power output (0-4kW) regulated by HA.
Which one?
Full version:
Looking to get a hybrid car.
I live in Italy where the maximum domestic power is capped at 6kW on 230V (cut off at 6,6kW which requires an outside circuit breaker to be reset).
Everything in my house is running on electrics: heat pump for heating and hot water, all kitchen appliances including induction hob, washer, dryer, …
So we regularly get close to the 6,6kW limit. At the moment I’m monitoring my consumption and Home Assistant sends a notification when we get close so we know not to put any other appliance on for a while.
The battery in the car I’m looking at is about 8kWh, so don’t need any fast charger or even type 2 charger. A cable on a ‘heavy-duty’ domestic plug (16A) should give me 3,7kW which means the battery charges in about 3 hrs, which is fine by me.
I want to install some kind of power plug that can regulate the output power so my car only charges when the consumption in my house is low or my solar panels are working.
Any advice on hardware? Either off-the-shelf or DIY.
I don’t know, but just so you’re aware your math isn’t going to check out in practice. You’d only charge the battery in ~3 hours with 100% efficiency at 3.7 kW, including conversion from AC to DC. What does your charger spec out at for input to output? I’d expect a considerable wattage drop…with 60%-70% efficiency max at 230 volts.
Whatever you choose, you’d have to be very very careful how you’re regulating the current. Ordinary dimmers would absolutely destroy a battery charger as they impact the frequency of the modulation. You’re probably better to use a lower amperage charger that will stay under the limit and then switch that load altogether so it only charges while you’re sleeping and not coming close to the limit.
I have never heard of a power outlet that can limit it’s own power output other than on/off or a dimmer type arrangement (which @blhoward2 points out is unsuitable).
Perhaps you are better off finding a charger which is controllable?
According to the manufacturer (Volvo), these are the charging times:
Name
Wattage
Time
3-pin socket
2.3kW
5 hours
Type 2 “Slow”
3.7kW
3 hours
So either I’ll use a normal socket with a HA controllable relay on it or look for a controllable Type 2 charger.
The Volvo app allows for charging to be scheduled, I’ll just wait and see if I can control that also with the HA integration of it.
I think you are probably over complicating things.
As you only have an 8kWh battery, why don’t you set set a timer on the car to charge from 01:00 - 00:60. You shouldn’t be drawing much at them times, so no need to switch on / off?
Then you get home from work etc plug car into the house. At 01:00 car starts charging.
You could look at getting a device similar to the myenergi Zappi 2.0 which I have.
That allows you to alter the charge rate. But do you really need to spend the extra on a Hybrid car? When you will only gain about 1kWh of extra charge speed.
Will start out with your solution of a timed charger at night and break my head afterwards on a smart plug/relay so I can control the charging with HA.
The whole reason I want to do it is to use as much of my solar power for the charging as opposed to grid power at night.
In that case you might want to consider an Zappi 2.0 or similar.
It has eco and eco+ modes.
You can either set a minimum solar % to use. Example 70% Solar 30% Grid.
Or to charge purely from Solar. Bearing in mind the minimum a car charger can go down to is 1.1-1.2kWh. So if the weather is rubbish you wont charge your car purely from Solar.
Although the Zappi is 7kWh you can restrict it’s current draw. Although as you can only put 3.7kWh into the car that’s not really a worry.
The smart charger is definitely a better solution than a relay turning the charger on and off.
Battery charging is a multi stage process. Interrupting this regularly will result in unnecessary wear of the battery and very inefficient charging
