Notification when battery is done charging?

I’m setting up a battery station that will be used for various devices. The ones I’m most worried about are my tool batteries. I don’t want to leave them plugged in and harm the batteries. I have a smart plug that does power monitoring. Is there a good way to monitor the usage and alert when it’s done?

Look at the values of the power usage when charging vs charging finished. If there’s a clear difference you can create an automation based on those values.

That was my thought, but how would you do that? If it takes 3 hours to drop back down, would that matter? Or can you just do “if power goes from 50% to 1%, notify”?

I’m not sure I follow. What does percent have to do with this? I thought more along the line that you could use a numeric trigger when the socket goes from 20W to 2W (charging to finished charging). You need to find the values yourself.