Well, in that case I would suggest to do straight road ride, for maybe a couple of Km and then measure the energy consumption.
Also, if the outside weather is cold im sure the battery will drain faster…
I havent really looked into this by much detail, but If im right, when riding out in cold, your battery could have 20% less capacity…
So, instead of example 10ah, it would get only 8ah out of battery.
And I guess when charging you would charge more than you actually drained.
But I havent really tested this but this is something worth looking into.
So in that matter, It would be best to measure consumed energy not the one you put back while charging.
Here’s an article I found:
But honestly, I would find someone who has better electronics knowledge and who can explain the Coulomb counter principle when charging. I suppose a wattmeter does count how many amps/volts goes to the battery = charged energy, but it might be that not all energy gets stored in the battery directly and some is lost in the process.
So here I dont know if wattmeter/charger can take this into an account or if the losses are bigger than 5%.
In my experience I think charged vs consumed shouldnt be more than 10% difference. But It could be more in cold weather, if what I said earlier is true. (needs more data from scientific sources)