I had this done up a couple of days ago, but for some reason, a popup from RCG brought up a new page and nixed the entries when I went back a page!
We were speaking about batteries and choices for flight times. What I forgot to mention is the choice in part one of battery capacity was also upped to account for a ~75% energy level in the batteries to maintain a decent flight time.
The 2200mAh battery being replaced by a 2600mAh battery is necessary to yield higher flight time (2600 is ~18% higher in energy content (and capacity). let's talk about energy first and how it relates to power and this will all become clear.
Energy is the TRUE indication of what's available in a battery for flight. Energy is volts times capacity:
E = V x C; where V is battery voltage and C is the capacity in Ah
Watts = volts time amps, or P = V x I; where i is current and P is power (watts)
but what voltage to use? It's easiest and probably close enough to use the median drain voltage of the battery system, or 3.7V/cell. under load, the battery will drain from 4.2V/cell to whatever cutoff (usually around 3.2V/cell) is set. The mid voltage for a lipo is around 3.7V/cell, so we use that to get our average energy available:
For a 3S, 2.2Ah battery, that's now: 11.1V x 2.2 = 24.42Wh
The 2.6Ah has 11.1 x 2.6 = 28.86Wh of energy.
When figuring flight times, take 75% of the energy figure as actual available flight energy;
28.86 x 0.75 = 21.64Wh.
So, we have in this case
...Continue Reading