this has been driving me insane for the past two weeks. built a 5inch on a stretched x frame, running a standalone 40amp esc (not a 4in1) and every time i punch the throttle hard ? like full send from a dive ? it browning out and the quad just drops. comes back after a second but obviously thats terrifying when youre 30 feet up.

i already checked the obvious stuff i think. capacitors are soldered on the battery leads, theyre 1000uf 35v caps i had laying around. battery is a 4s 1550 from a brand i dont really trust anymore honestly. fc logs show the voltage spike right before the dropout. im not sure if its the battery not being able to handle the current draw or if theres something going on with the esc itself. the esc is getting warm but not hot, like i can hold my finger on it.

running betaflight 4.4 and havent really touched the motor output settings beyond the defaults. any ideas before i just swap the whole power system out

sounds like the battery tbh. a 1550 4s being pushed hard under a throttle punch can sag like crazy if its an older pack or a low quality one and your fc sees that as a brownout condition. try with a known good battery first before you blame the esc. also 1000uf caps are good but check how youre soldering them ? ive seen people put them on backwards or with cold joints and they basically do nothing.

the esc being warm but not hot is probably fine, standalone escs run cooler than 4in1s in my experience because they have more surface area spread out. if you have betaflight logging set up look at the vbat graph right as it drops and if you see it dip below like 3.4v per cell under load thats your answer

yeah what he said about the battery. i had almost the exact same symtoms last year and spent forever looking at my esc and fc config and it was just a puffed 4s that couldnt deliver the amps anymore. once i put a fresh pack on it it never happened again. kind of embarasing how long i debugged the wrong thing