I’ll put my 2p in:
1. Depending upon state of charge, charger speed and how many others are charging (compared to capacity of the supply) you can do a splash and dash but I’d argue that stopping for 10 minutes would double the benefit without costing a stupid amount of time. Mathematically if you’re charging at 100kWh for 10 minutes that’s a sixth, which would get you about 16-17 kWh. If you’re getting an average of 3.5 miles per kWh then that’s about 55 miles.
2. Charging to 100% to stand isn’t advised. However, both the charger and car can be programmed to charge to 80 or 90% at which level you should be able to let it stand without risk of damage. What power gets lost depends greatly upon what is running whilst the car isn’t in use. Some cars can be set to wake up and heat the interior (for example) at a set time daily, that can dramatically reduce the charge level.
3. I’m not sure of the battery capacity in the BMWs but if I were to do a 20-80% charge overnight at your cost per kWh then it’ll be 46.2 kWh costing a smidge over £11 per charge. Estimating 4 miles per kWh that’s around 6p per mile.
4. The 20-80 range is mostly for rapid charging as outside of that the battery software slows charging for protection. That means you’re effectively using 60% of the battery so 120 of the 200 miles. However, if your journey is from home, then you start at 100% and then boost up by the numbers discussed above. So you’d still get 200 miles plus a little extra for your pee stop.
5. You have to have a smart meter for an EV specific tariff, most of which charge you a little more through the day to save you extra overnight (5-7 hours). The likes of the Octopus Go and variable tracker tariffs may allow a set rate for vehicle charging without needing a specific time but will still need a smart meter. Not having a smart meter just means the cost per kWh is set either at a 24 hour rate or economy 7 if the meter is set that way.
What you will get used to quickly is the convenience of plugging in when you get home on a charging night and ignoring the car until the morning when it’s fully charged or charged to the predefined level.
On longer journeys, follow the motto ‘charge when you stop, don’t stop to charge’ and you should find things most enjoyable. I find we stop at the same place for years, it’s usually about half an hour which in the Ioniq 5 with its 800v architecture means it’s nearly refilled when we get back to the car.
I'm Autistic, if I say something you find offensive, please let me know, I can guarantee it was unintentional.
I'll try to give my honest opinion but am always open to learning.
Mark