Real range vs. declared range?

Dunno if there are any "grin" fanboys on this list here but the grin "cycle analyst" gives you a lot of quality info. I think i've only scratched the surface of what mine can do. In-the-moment speed and power read-outs, and it will tell you the watt-hours left, and calculate the honest watt-hours of the battery itself (nice way of testing manufacturer specs).
Is it this? I didn't know about! Interesting...
I feel like a decent understanding of the drag coefficient could just be to cruise on flat and record watts at differrent velocities, and extrapolate the coefficient.
How do you know how much power you need to cruise at a certain velocity if you have no throttle?
For your thoughts and suggestions,

I just finished 1 of 3 throttle tests, to find a realistic average, with my new Jugg 4 bike, with the 2 - 52v/1754whr total, tire psi was 25/30, and bike weight of 100#'s + 200#'s for me, just using the throttle set at 11/12 mph and then will do 3 tests pedaling using eco 1 (no throttle usage).

1st throttle test = 63.1 total miles in eco 1 step and used 589.52 WH
for and average of 9.34 wh p/mile, all throttle no pedaling,
for an average of 12.35 mph, (my average pedaling speed),
2000' + elevation change,
average wind speed 10/12 mph, (head wind for half the test,
then tail wind), for the trip home.
The Low Voltage cutoff point was 45.4v (end of test) for these 52v battery's.

I did the same tests with my Wart Hog MD 750 with 48v/1440whr
and got an average of 80/Throttle and 120 mile/pedaling, eco 1 step.
Yeah, it took me a while to figure out that mfr range estimates were for Class 1 PAS 1 middle gear with a tail wind and still inflated 100%. Lol
To ask a question, What is the average weight of your bike and you on board, and tire psi?

I heard from others and can confirm myself with data from three ebikes/batteries that it is pretty accurate.
Very cool chart.....I plugged in my numbers.....seems very accurate. Chart says I should get about 21.5 miles......I usually don't go that far before charging....I usually charge around 17 to 19 miles......which can be 3 or 4 rides for me. I have a 48v battery......when I get down to the 43 or 44 v zone.....I charge up.
Being the reasonably unfit, fattened turd that I've become, I found that on my regular ride I cover 15-20 miles and use about 20% of battery.

Here's the deal, though: I pedal. Based on stationary bike data, my pasty white legs put about 100-150 watts to the crank arms. That is good enough for an average of 15 mph on a flat road. I can do that for a couple of hours. Point me uphill and I get wheezy. I use the gears to keep myself at my optimum pedaling cadence, not too low because knees, and not too high so I don't bounce on the seat.

So, on the 65 lbs Denago, I figure I pedal the same amount as always, but the bike has to help up hills and any mild inclines. The 14ah, 48 volt battery translates to 672 watt-hours. If the 500w hub motor has to help me an average of 150 watts, I get over four hours of power. 4 hours x 15mph = 60 miles. This checks out given the battery consumption I observed so far.

The other element which I feel helps my range are the tires. They have a "city" tread, not the knobbies found on most ebikes I see people ride. Ditch the knobbies. They are loud, inefficient, and puncture-prone. I like Schwalbe tires for their puncture protection and I would recommend them. They have a proven bicycle touring record as some of the toughest tires out there. I set my tire pressure to just take the edge off small square bumps, such as joints in sidewalks or cracks in concrete. Any less pressure and you lose rolling efficiency.

So, there you go. It's that easy.