I thought I would give you a little time to do the math, because I made a mistake, or posted a mistake. Apoximately 22 volts is the 0% mark, not 19.92 and as I said earlier I haven't figured out DJI algorithm yet but it is most definitely a sliding scale. Once past the 50% mark the percentages drop at a much faster rate and yes I did miss that, but will figure it out.
So if you went by the 6 volts from full to falling out of the sky you would have been really shocked when your drone stopped flying at 22 volts. I'm posting my mistake so other will fly by DJIs percentages and not my miscalculations.
So how did I discover this, by flying the Inspire until it wouldnt fly. fortunately it was about two inches off the mat when she said that was it, I'm done flying. I know, this isn't the orthodox way of doing things. Funny thing percentages showed 0% when she came to rest.
I'm sorry but this is a very dangerous assumption to make.
The problem is there is no true correlation between cell voltage and percentage - only a bad approximation.
As said before, DJI ''Smart" packs were introduced to weed out the idiot gene.
As professional operators you really shouldn't be flying by a 'best guess' arbitrary percentage approximation of fuel capacity.
Percentage is simply a guess (by the software/algorithms, whereas voltage is an absolute (and accurate) measurement.
There are too many variables to factor into a percentage reading including but not limited to - age of cells, internal resistance of cells, how a pack has been treated and/or stored in the past. The weakness of any particular cell. How the cells track together and mV difference between them under load. How well the cells recover when load is removed (rebound).
If you Google Lipo voltage v Percentage you will get 50 different opinions!
Obviously any discharge curve will not be linear. Lipos simply don't work like that - they never have done. Lithium Polymer chemistry means they give a faily flat discharge initially and will plateau. However, there is a very small difference between the last phase of discharge and falling off that plateau which ''Fuel type guage or percentage readings" can never do accurately.
What will be '15%' battery one day will be '12 or 10%' another day as the packs age or so many other factors.
Fly by voltage - it is safe, it is absolute and you will not get any surprises.