Power consumption during last power cycle

[spark fog]

Hi all,
I have a very simple question and don't want to spam the forum with this. I tried Google Gemini and it was quite frustrating ...
I have a smart power outlet, connected to a car battery charger, and I would like to know how much kwh went into the battery during the last charge.

I know when the charge starts: I turn on the power outlet.
I know when the charge stops: An automations turns off the power outlet when the power consumption is below 1W - can be expected to have fully loaded the battery.

Now the question is how to turn this into an automation.
I tried the consumption counter ("Verbrauchszähler") in HA, but it stays in "unknown" ... 10 minutes have passed and nothing happened.
The battery is currently charged with 15W, so it's not nothing.

Do I need to use the Riemann integral for this? Gemini said that this was more difficult, but I'd be up to it if this was the correct route.

[echo minnow]

i do something similar with a utility meter helper tracking a total consumed entity. and when a charging sessions starts i reset the utility meter.
if you can seperatly track the actual battery charge from the car you can calcuulate the charging efficientcy

what entities does your smart outlet have?

[spark fog]

ugh, it actually worked ... I just had to wait longer than 10 minutes it seems. Maybe the 15W consumption was not enough to show 1W after 10 minutes

It now displays 5W and even went up to 6W now

Thanks mate!