Let's Control It

Hello!

I´m sorry if my english is not so good and badly translated words might appear in your eyes

So the idea behind this is that we have here electric (220v ac) poles at yard and parking slots where we could connect our cars to heat at winter but there are no timers in them (-5c--25c pretty regular at winters but it can vary from +4c - -45c). Basic solution for that is the regular timer between the socket and cord but thats just not good in general if we think of saving energy and not overheat engines coolingliquid.

There are solutions of using esps and others with Openhab, Home Assistant and Domoticz with RF433/Zigbee/++, but im asking that is there even thereabout idea of using esps as standalone unit with these capabilities
- Weekly programmable leaving time with wifi and using relay for needed time for heater control (Ambient temperature reading and heating time adjust for that) (Maybe Google Calendar?)
- User manual button for 2h direct heating
- multiuser for 2 or more cars
- Standalone, so using RTC needed or using time from internet
- Wifi connection loosing cannot interrupt operation
- Case heating, not so necessary
- Car inside temperature reading, not so necessary

I'm curious to where you live, as it may get -45C.
Also you really should take care of the choice of relais as you don't want them to stop working. (either getting stuck at closed or opened state)

My suggestion would be to use a temperature sensor and the rules engine in ESPEasy to make sure you're only heating what's needed and when it is needed.
Things you make use as a trigger for switching on/off can be humidity and/or temperature.

What kind of current are we talking about to switch here? Is it just a few amps, or are we talking about 5A or more?
When > 5A, I would definitely not go for cheap Chinese stuff like Sonoff's and maybe even consider a solid state relais. Just make sure those also need cooling and those for AC only can switch on AC as they switch at the 0V crossing. (so don't switch on DC)

You could add a GPS unit for keeping track of time when no WiFi connection is available.

Does the cars already have a 230V heater installed?