BEC/Servo problem

[REVO-DADDY]

I am running a CC BEC off a 1600 2s lipo, and when it was set at 5v everything worked fine. I bumped up the BEC output to 6.5, and when I turn the wheels the green light on the BEC flickers and my throttle servo(nitro sorry) jumps. My Steering servo is a 9100T so I would imagine it has a decent draw. Is it just drawing too much at 6.5v or is the servo bad. Every other servo I have worked fine at 6.5v, so I have to believe its either drawing too much or it’s bad. Can anyone help explain to me what is going on here?


P.S. You may be thinking that I should not be running at 6.5, but even a fully charged 5 cell nimh is almost 7v. So I have to believe this servo should be fine at 6.5v

Thanks for you help! Steve

[lincpimp]

Is your lipo fully charged? The voltage may be dropping below 6.5v. Honestly that servo does not really need more than 6v, change the ccbec and see if it does it still.

[REVO-DADDY]

thanks lincpimp

It's about 2/3rds charged. It does not do it below 6.0v. Are you meaning to change the BEC?

[BrianG]

Even though a BEC utilizes low drop-out voltage components, you still need a solid 1v higher than your BEC output to operate. This is true for linear or most switching BECs (I've seen a couple designs that will boost or buck as needed). Failure to do this results in unstable BEC operation under load. And you can't verify with no BEC load because only under load does it get unstable.

Setting your BEC to 6.5v would require around 7.5v to work properly/reliably. You can maybe get away with as low as 7v, but that doesn't leave much room to account for battery voltage dips under load, which destabilizes the BEC.

I can with 99.5% confidence guarantee this is what you're experiencing.

[lincpimp]

Originally Posted by REVO-DADDY

thanks lincpimp

It's about 2/3rds charged. It does not do it below 6.0v. Are you meaning to change the BEC?

No just change the setting of the CCBEC to 6v and try it out. BrianG's explanation above is the reason you are having the issues.

[Arct1k]

I'm 91.3% confident in BrianG's response...

[BrianG]

Only 91.3%? Ouch, that hurt.

[REVO-DADDY]

I am 100% confident, going to charge my lipo.... thanks guys!