Implement average speed planning

🚧 THIS IS A TICKET MIGRATED FROM UPVOTY. The original ticket and comments will be available for a limited time over at:
https://abrp.upvoty.com/b/request-a-feature/implement-average-speed-planning/
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Hello team,

The product is awesome, but it barely gives accurate data and planning is way off. Many times I've got to the charger ABRP suggested with at least 10% more than expected.
I think this is because ABRP assumes that you'll be travelling at the maximum speed you set up, but more often than not, this is not the case.
Reference speed option is badly explained, literally no docs on it nor examples of how that works (if it works).
For instance, on my Hyundai Kona 64 kWh, with 120 km/h set on ACC (adaptive cruise control), I traveled from Effingen, CH (starting at 100%) to EnBW Germering, DE, 348 km (I think) and arriving with 16%. This trip was done at 04:00 in the morning, with virtually no traffic, and no holding off behind trucks or anything.
However the planner told me that I sould have at least one stop either at Thalheim, CH, or in Dorfen, DE, suggesting to me that I would need an intermediate charging session.
The car reported a consumption of 158 Wh/km and I averaged 93.8 km/h.
So please implement a way to accurately plan the charging stops, at least based on recent trips.
In winter I see a lot of very bad planning from ABRP. A charging stop where ABRP suggested I would arrive with 11%, I was arriving with 32% on the battery. That is very very bad.
For the above example, in order to achieve the same result in ABRP I have to lower the reference consumption at 110 km/h (I don't know why is that value over there) to 130 Wh/km and I can't see other consumptions at other reference speeds in order to properly tweak them.
Therefore:

1. Please implement an average speed option where the planner would take that into consideration. Ideally make it based on more recent data
2. Please expand documentation on "reference speed" option with examples
3. Please expand on the car's profile to include readouts at various speeds (50, 80-130 km/h) and allow them to be editable so that the planner could have substantially better results.