Hi there,
I'm building up an Octocopter (4kg with Battery) and till now everything was very successfull (PID tuning etc.). A few days ago I changed to the new firmware 3.01 (and to my new radio, from Spektrum DX6i to DX8) and the problems began.
When trying alt hold and loiter (I guess even in stabilize), the copter sometimes descends a little bit too much and I switch back to stabilize to avoid it go back to ground. Although at full throttle, nothing happens and the copter (luckily not too hard) crashes to the ground. Till now, my landing gear absorbed every crash but some were really tough.
I got a logfile appended (crash is around 30.000 and I enabled all log settings), you see it descending really fast, although I try to push it up with throttle at 100%. After that crash, I tried some throttle-pushes from hover and nothing really happened at 100% throttle... I know the copter is not that light with 4kg, but hover is around 60% (ecalc said it should be below 50%...) so there should be some power left. Can someone help me find the problem?
Replies
I think I found the reason. There is something wrong with the batteries. I use 2x 5000maH 3S 25C batteries on my Octo. Today I found out (with two different packs), that at 11.1V (with my DX8 Telemetry) the Copter had no more power to climb and some seconds later went to the ground.
Back at home, the cells were at 3.85V each and I could only pump in about 2600maH in each battery, so there should have been quite more flighttime left. Last week, everything was OK and I could fly my batteries all until they were emtpy (80%). What could be the reason for this? Also with brand new batteries there is this effect now.