Batteries drop voltage very quick

[Buddig]

Hi there -
I'm doing a project with a Quanum 680U Pro Y6B copter with six 4010 T-Motor, 13" CF props and TWZ Spider 30A ESCs. And a Pixhawk flight controller.
At this stage I'm trying to calculate which batteries I should use in order to get the best performance and for a test I have tried to put two 3S Turnigy 2200 mAh 20C in serie to get a 6S. Regarding to the documentation I should properly use 4S and 15" props, but this was my first test.
I'm using a Turnigy Watt meter to measure the Amp, voltage and watt during the test.

At start the voltage is 24,5V - I keep the effect at 290W and this draws between 12,5 to 13A to make the copter hoover (I prevent it to take off), but let it stay drawing 290W and measure the time before the Pixhawk turns into to Failsafe mode, set at 21V.
After only 2 minutes and 30 seconds (at 290W) the voltage has dropped to 21V ??
The Watt meter tells me that it only has used 0,5Ah of the capacity and after the motors stopped the voltage raises to 23,2V.

Is this a common issue for batteries or will another brand make it better.
I assumed that I at least could draw between 1800 and 2000 mAh before it reached 21V and not only 500mAh before the voltage dropped to 21V.
And I didn't expect any problems drawing less that 15A when the batteries says 20C

I hope that some of you have some usefull input/comments - And maybe Bruce will bring this up in a Weekly briefing

THANKS Bruce for some VERY informative videos on your channel - I enjoy to listen to your knowledge and your wonderful attitude.

Best regards and keep up the great work

[singerbear]

It sounds like you're experiencing significant voltage sag under load, which can happen for several reasons. Even though the Turnigy 2200 mAh 20C batteries should theoretically provide sufficient currentmoto x3m

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