I have been looking at specs posted by t-motors on the 300KV motors:
Lets assume a model mass of 3kg(1.2kg of batteries the rest dedicated to the chassis, motors and controllers) on a quad, this is 0.75kg per a motor or 750grams of thrust to sustain hover. A logical approach would be to find the highest efficiency(Thrust/power) for the given hover mass. Doing a visual interpolation of the table(:)---->always wanted to say that) the DJI 15X5.5 would be the most efficient to sustain this mass at hover. In theory does this mean at roughly 60 watts(yes great visual interpolation), using V=P/I, I Will be able to use a 22.2v LIPO with capacity of 12000mah for 1hr? Surely this logic is flawed?
In my personal capacity I have run many motors on a rig that I have developed and this logic baffles me unless t-motors have hit gold.
You are correct the mass of the batteries were under estimated. I wonder what the break even point is currently.....i.e. (when adding more batteries(mass) to achieve a better flight time become negated by the payload(batteries))
Using MotoCalc , the thrust & power consumption values do seem to come very close the specs. in the table using an APC 14 x 4.7 propeller ( There is no DJI prop in the MotoCalc database)
However, a 6-cell battery (or batteries) totalling 12000mAh in capacity would weigh about 2 Kg.
So now the total all-up-weight is more like 4 Kg, and each of the four motors needs to provide 1Kg of thrust, and the amperage increases from 3 to 5 Amps each (about 110 watts), reducing the flight time to about 35 minutes (+/- 3 minutes)
The motors weigh 205 grams, the T-40 ESC's are 35g each, totalling 960 grams not including propellers or prop adapters.
My number crunching was not scientifically rigorous, but its good to first approximation or(10%).