Payload vs flight time testing
I've tried to eliminate as many variables as possible so that I can make as accurate comparison as possible.
- all tests were performed indoors over two days (hover test) - no wind and minimal temperate and pressure variations.
- I used 2 different DJI batteries (I only have 2!) to minimise the chances of using a battery with uniquely good or bad characteristics (both started on about 30-40 cycles).
- each test was repeated 3 times in order to gain an average.
During each test the battery %, mah and voltage were recorded at takeoff and upon landing. The flight duration was noted. Most flights took off at 98% and were landed at 15% battery. The hover was at 0.8/0.9m.
I conducted 3 test flights with each of the following payloads:
0g (control), 200g, 400g, 600g, 800g, 1000g and 1200g.
- For each test I calculated the average mah consumed per second (rather than converting into power / watts - amps etc...)
RESULTS
No payload. 3.5 mah per second (210 per min)
200g. 4.2 mah per second (252 per min)
400g. 5.0 mah per second (300 per min)
600g. 5.9 mah per second (354 per min)
800g. 6.9 mah per second (414 per min)
1000g. 8.2 mah per second (492 per min)
1200g. 11.2 mah per second (672 per min)
1400g. Test aborted - discharge overload warning
On average each test consumed 3640mah (about 85% of the battery capacity).
CONCLUSION
There is a steady increase in power consumption as weight is added upto apx 1000g. At 1200g payload the power consumption increases significantly and at 1400g the bird took off but hovered for only 15 seconds before one of the battery cells (as displayed in the DJI Go app) went red and triggered several warnings. The bird was clearly struggling to hover and I aborted the test. I'm not sure what the maximum payload is but I don't want to trash my batteries or set fire to my P3 (or house!).
I have done these tests to work out the theoretical best match for different batteries combinations - I say theoretical because I haven't bought any other batteries just yet and I can only go off what each of the battery manufacturers claim the capacities and weights to be.
Theoretical hover times using 85% capacity:
1 - 30min 36sec - 1 x MultiStar 16,000 mah battery (remove DJI battery) - 831g @ 7.1 mah/s
2 - 28min 28sec - 2 x MultiStar 5200 mah batteries with DJI battery - 836g @ 7.1 mah/s
3 - 27min 39sec - 3 x standard DJI batteries - 732g @ 6.6 mah/s
4 - 27min 35sec - 2 x MultiStar 6600 mah batteries (remove DJI battery) - 714g @ 6.5 mah/s
5 - 26min 58sec - 2 x MultiStar 6600 mah batteries with DJI battery - 1064g @ 8.9 mah\s
6 - 26min 54sec - 2 x MultiStar 4000 mah batteries with DJI battery - 690g @ 6.3 mah/s
7 - 26min 14sec - 2 x Hyperion 5200 mah batteries with DJI battery - 932g @ 7.7 mah/s
8 - 26min 13sec - 2 x Hyperion 3650 mah batteries with DJI battery - 640g @ 6.1 mah/s
9 - 26min 9sec - 2 x MultiStar 5200 mah batteries (remove DJI battery) - 486g @ 5.4 mah/s
10 - 26min 7sec - 1 x MultiStar 10,000 mah battery (remove DJI battery) - 444g @ 5.2 mah/s
I have assumed 2 ways of mounting batteries:
1 - in parallel with a DJI battery,
2 - as a replacement to a DJI battery - as shown in page 40 of this thread.
Based on these results I am going to buy and test the MultiStar 16,000 mah and 2 X MultiStar 6600mah.
I've only listed LiHV batteries that I can get in the UK but I could add some others to this list to compare if people are interested (need weight and mah). I would be interested to see if the theory is similar to people's experience.
I'll post some photos of the tests.
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