BobT No worries on the time taken to reply.... always as when one can.
I am glad you have had success with a charge slot during the Peak [05:30 - 23:30] now charging your batteries as well as your EV.
Yes, manually stopping a charge will not affect a slot that has been provisioned and should carry on until the end of that half-hour period, including the assigned 'off-peak' rate associated with that period.
I would seriously urge you, however, not to manually stop or interfere with the scheduled charges. This is where you could end up in a bit of a mess to be honest.
If I may use an analogy to illustrate.
You have a journey to make that is at least 200 miles away. You have two choices: use the old manual method of a map [manual] or use a SAT NAV [Automation]. You opt to to use SAT NAV and get partway through your journey. You then, because you don't like the route taken ignore the SAT NAV and take a different [unplanned] route. This is where it can all go wrong because you are now travelling down an unplanned journey, and you don't know where you are or which way to turn next. You can then end up in a traffic queue that would have been avoided by the SAT NAV. You get the point.
This is a bit like what you are doing here with your setup.
You need to let the automation [IOG + WW] either fully control your setup, or you need to manually do everything.
The EV battery State of Charge (SoC) [battery level] - or as Octopus call it Charge Target is how you control your charging. If for some reason, you need the car to stop charging early, then set this Charge Target to a value that is lower than your EV's current SoC. This will then update IOG, who will bring to an end your slot allocations, this will then be picked up by WW, and you will switch back to normal Peak hours operations, where your house load is met with your batteries.
I use this Charge Target value to control how much I want my EV to charge to on a given day. I never stop a charge mid-way through. If I do need it to stop, I follow the process above and change it in the Octopus app. I then let the automation catch up. This avoids battery drain into EV or slots being charged at Peak rates.
Hopefully, this makes sense.
