Greetings and my very first post here...
Seems this has been answered but I thought I might add what happened to me when I couldn't lift off after my new F450 build... I had just recently purchased, for another application, two new 2800mAh Zippy 25C 3S Lipo's, that again were brand new and fully charged... I like to do voltage checks right after coming off my charger and both of these new batteries were reading right around 12.51V...
I installed them one at a time and attempted to spool up and at maybe at 70% throttle my 450 was just sitting there without coming off the ground... Within a couple seconds her Naza Lite controller would bring down her throttle so I couldn't raise it anymore from my DX8, and she went into a fast red flash error..
I Powered down and exchanged batteries and again over and over she would go into fast red light error right before lifting off... Her MPU would take away my throttle so I could spin up no more than maybe 25%... This baffled me for days because I could easily fly with an old ThunderPower 2500 4S 35C...
Then one of the guys on another forum suggested soon as I go into error to disconnect my battery and throw my digital voltmeter on her and see where she was at so I tried it... Right off the charger they both measured 12.5V and in less than a minute of attempting liftoff, and going into red flash error, I measured them and they had fallen to 7V...
My brand new Cheapie-Zippy's were no good... I ordered 2 new 2800mAh 60C 3S Turnigy Nanotech's and she then flew perfect and super strong... I now fly 3S 5000mAh 65C's and get safely 12 minutes of light flight at 1580 grams total up flight weight, with EzOSD, 1.3gHz Vtx, Pro700 FPV Cam, Landing gear, and a Mobius camera...
I've only been flying FPV almost daily now for 4 months and am still a beginner as it's learning curve has been way more than I ever thought it would be but I simply love it... I really learned that even new batteries can fail and that is what kept me from lifting off as my voltage fell so fast under load...
Happy Flying and Peace...
bnick
Gresham, Oregon
KG7GNR