The big fly in the ointment for me, which doesn't affect you, is the idiotic and facile change by Volkswagen to their API to stop customers from being able to use the API for personal use. As a result, the VW Connect integration doesn't work and so my ability to see whether the car is at its target charge level or not is now non-existent. As a result, if we see negative pricing then we're setting the car to charge at a preset time (once again through HA using a date/time helper, but it's still more manual than it needs to be).

The way my automation works is that if my wall box changes status to "Charging", I set that minimum SoC to 90%. That doesn't mean the inverter will suddenly start charging the battery but it ensures that if the battery is at anything less than that the charge in the battery will not be used to charge the car. I also, of course, have another automation to say that if the wall box status changes from "charging" (i.e. the car isn't charging any more), I reset that minimum SoC back to 10%.

One of the features of the Zappi, as you know, is that it has an Eco+ setting, meaning it will never try pulling from the grid. If the inverter can supply 1.5kW or more, the car will charge using all available non-grid leccy, but if it drops below 1.5kW then charging will be paused. The reason I set the home battery's minimum to 90% is that on cloudier days it is possible for bouts of great solar to be interspersed with less than 1.5kW periods. By having that last 10% in the battery potentially available, it has the effect that my home battery will fill first in the morning, export to grid will then ramp up to more than 2kW, at which my car (if it's connected and not at its target charge level) will start charging. If the sun goes in, that Eco+ charging will still continue with some coming from solar and some topping up from battery until either the sun comes out again or the battery depletes to 90%. If the sun comes out again, the inverter will split charge between battery and zappi, so my buffer is regained. In effect, it stops the zappi stopping and starting when there's a bit of cloud.

Back to your situation, I can see in the documentation for your Huawei_solar integration that there are a number of configuration entities listed, but the names are foreshortened so not entirely readable. One of those, I suspect, will be the setting you want to play with.

I think this should work fine during night hours on IOG and if the battery is already charged, then it will have no effect, and if it isnt then it will charge the battery at cheap rate along with the EV. When the EV stops charging I have another automation that cancels the forced charge.

I then got to thinking, what would happen when IOG charges outside of the cheap rate window, presumably if the battery is below 95% then it will start charging along with the EV but still at cheap rate. So far so good.

But then I thought what will happen, if I plug the EV in during the day and it starts charging because I have surplus solar for example?, Now the battery could start charging when it isnt at cheap rate. But will it actually draw from the grid or just attempt to share the solar surplus?

Could this situation be prevented by changing the default mode of the Zappi so that it doesnt use excess solar? Or should I add another condition that detects when I am exporting solar? How do you handle it? Cheers in advance :-)

Just an update, all going well and have managed to stop battery discharging into EV I think. Will know for sure next time I need to charge in the day :-) Thanks again.

In that case, I suspect you've quite enough already to be able to fill in the gaps easily. Happy for you to shout if you need anything more, and in that case I won't go quite so basic in the explanation.

That said, it's now also worth making a more detailed list of things you want to achieve. By "detailed", I also mean including enough explanation to deal with any gotchas you can see.

For instance, one gotcha with the EV charging is that it will be regarded by the inverter as load just the same as the fridge or heat pump. However, you don't want to be charging one battery (your car) from another battery (your Luna), so it's well worth putting in place an automation or two to deal with that. For me, that means one automation to say "if the EV is charging, set the home battery's minimum SOC to 90%" and another saying "if the EV is not charging, set the home battery's minimum SOC to 10%".

As a result, you can come up with a list of IFTTT (If this then that) statements that describe what you want to put in place. It helps a lot in knowing how to structure your automations. I can happily share what I have, although you'd have to remember I am on Octopus Agile so they might not be entirely suitable for you.

I got the script to work using the actions tab in the developer tools, I need to cement my understanding now on how to include that in an automation or yaml file. Still, its a positive move forward :-)