Battery flight planning; use the battery gauge and use common sense too.

Former Member · Oct 14, 2018

I see so many threads here about people having to land in the middle of a dense forest, or in the middle of a lake because they misjudged their remaining battery level. Even though the level is prominently displayed on both the Mavic Pro and M2 controllers, in addition to being on your device's display, I would not rely on it to extend your flight time when it gets below 50%. I always plan to land with 30% reserve battery, or 25% if Im close-in.

While the battery meter in the Mavic is pretty accurate in measuring voltage at the moment, that doesnt necessarily mean that the battery will discharge evenly and linearly. Most Lipos pack their punch in the first half of the battery, with the second half tapering off quite rapidly. Any motorcycle owners out there might be familiar with a motorcycles analog fuel gauge. On my old Road King, I could go 150 miles on the first half tank, then only 50 miles till I ran out of gas on the second half. I could almost watch the needle move as it went from half to empty.

My point is that you should plan your flight to land with 25-30% battery left. In battery planning you should take into consideration some of these factors:

Time of day - Plan to take off and land in the daylight if you are not an expert or commercial operator
Estimate your time to climb to cruise altitude,
Estimated your cruise time at altitude,
Estimated your descent time.
I also like to take into account a "what if" situation, where in the event of a dog, kid, or other distraction, I can hover until the obstacle has been cleared. 1-2 minutes works.
Wind direction - Best to take off into a headwind and return with a tailwind.
Wind velocity - Dont underestimate the power of winds aloft. Wind speed and direction can also change midflight, another factor to consider.

If you are conservative in your planning, plan for contingencies, maintain your batteries through their lifespan, and listen to your gut, you will enjoy years of safe, trouble free flying.

Best to all.

Rob

P.S. Dont forget to enter the Fall Foliage Photo Contest.

Fall Foliage Photo Contest. Prizes for top 6 entries.

Gecko10 · Oct 14, 2018

Great article. Thank you, sir.

WithTheBirds · Oct 14, 2018

Very good advice. No full size aircraft pilot would plan a flight to be landing on fumes. We need to allow for the unexpected scenarios (being caught out by the strength and direction of prevailing winds is probably the most common).

Notwithstanding we can have significantly higher confidence in the accuracy of our battery % gauges than was offered by simple coulomb counting strategies that were employed in the not so distant past. The % remaining is not simply derived from cell voltages. It is a significantly more complex algorithm which looks at average and instantaneous current draw, cell Internal resistance, voltage drop under load, temperature and other factors including the derived life (health). The flight time remaining depicted in GO clearly demonstrates how well the fuel gauging works.

We do get a nice benefit from landing with a bit more in the tank- significantly increased cycle count and a long trouble free battery life.

sparkorc · Oct 14, 2018

For those that do get caught out with a low battery on returning to home into a headwind, you will most likely find lowering your altitude the wind strength is likely to be less severe.

charliesRig · Oct 14, 2018

" Sports mode"
should be used with caution Because the discharge rate could be severe.!

Aways check to make sure your battery is seated Properly in your craft before Flight

.............I do like that thought (take off into head wind return with tail wind ) VERY NICE.!....cR
.

Possums · Oct 14, 2018

WithTheBirds said:
Very good advice. No full size aircraft pilot would plan a flight to be landing on fumes. We need to allow for the unexpected scenarios (being caught out by the strength and direction of prevailing winds is probably the most common).

Notwithstanding we can have significantly higher confidence in the accuracy of our battery % gauges than was offered by simple coulomb counting strategies that were employed in the not so distant past. The % remaining is not simply derived from cell voltages. It is a significantly more complex algorithm which looks at average and instantaneous current draw, cell Internal resistance, voltage drop under load, temperature and other factors including the derived life (health). The flight time remaining depicted in GO clearly demonstrates how well the fuel gauging works.

We do get a nice benefit from landing with a bit more in the tank- significantly increased cycle count and a long trouble free battery life.

Me - misjudged my fuel "just a tad" over the Lake.