Hay guys and girls need help

Hay guys and girls I need some help so I built a 5inch drone the motors are the emax eco2 rated for 3s to 6s my ESC is 3s to 6s as well I was flying well on my 1100mah 120c 6s lipo and my 4s 1500mah 70c lipo I was also flying with 3s 2500mah 60c lipo so I had issues with the 6s it was pulsating the 4s and 3s was flying fine till about a week ago I changed my rates since then I have put back but the 4s batterys are pulsating now I don’t understand why is there rates I need for 4s and 6s batterys

What KV rating are the motors? When it says 3s-6s thats the range that the motor type (eco2) will take but its the KV rating that will determine what battery voltage is suitable for your specific motor

Betaflight? 4s should be good. 6s, cut the pids by a third. I guess raise them by a third for 3s

The kv is 1900 I was running them on the 4s for a few weeks no worries but as of late it’s just not flying right but on the 3s it’s fine

Yea bf I was thinking change them but I don’t know what too to make it fly better. I blow a motor a few weeks ago messing with the PID so not sure what to do

Really, for your kv of motor you should only be running 6s. But for a regular build, id suggest cutting down the pids by a third all round. If you are on the newer slider pid betaflight, reduce the master slider down to 60 percent ish.

Check your frame and frame bolts are nice and tight first. No flex or slack

So I can’t run anything lower then 6s on that kv why do the 3s fly fine but not the 4s also the motors get hot on 4s

What I mean is the kv is best suited for 6s. No problem running 3 or 4s, just wont be as quick.
The higher you go in lipo voltage, the lower your pids should go. If your motors are hot its because the ‘d’ term is working hard to tame the ‘p’ term. They need lowering.
You can program betaflight to auto select a pid profile depending on what size lipo is plugged in.

You have to tune it for each size lipo. As a rough idea, from 4s to 6s, the pids should drop by about 1/3rd