ESC brownout! Nub question here

[mesolost]

OK so the one ESC I have works just fine until the LiPo cutoff come up at which point the receiver browns out, motor keeps running but the entire system, or at least the 3 axis stabilizer, browns out and all my control surfaces do a full deflect and return to normal operation. So my question is, is it totally a bad bad no no to use 2 ESC's with BEC's?? Why 2? Because I have a brushed ESC functioning as an LED switch but it has it's own separate power pack. (2 cell for the plane and a small 3cell for the 12v lighting) I've pluged it all in and it all appears to work just fine but better to be safe than sorry so I thought I'd ask the fine FT experts here if it's ok. Tested the brushed ESC and it can only power the system for 45 seconds before the BEC on it (brushed one) does an oscillating failure BUT I only need to maintain power for about 5 seconds for the primary brushless ESC to stabilize. Again just need to know if 2 BEC's are bad. I felt I should ask after seeing so many MR ESC combo packs with 3 standalone ESC's and only 1 with a BEC.

EDIT: 2 is 1, 1 is none! Always have a backup!

 

[Craftydan]

Running two regulators on the same power bus can be risky. it may be just fine, it may not -- if the two regulators disagree about what "5V" is, one will charge the other trying to keep the voltage rail where they want it, stressing the parts.

On the other hand, you *could* run all your electronics from the 2S + brushed ESC side, and run only the motor from the bigger pack. your servos and RX won't care, assuming the 2S pack isn't too low. you won't have the heat buildup and voltage sag on the main ESC browning everything out.

BTW, double check the cooling on your main ESC -- it may be getting uncomfortably hot under load if the UBEC is sagging.

 

[mesolost]

Ok but it's the brushless on the 2cell and brushed on 3cell. And I wanted to know how the LED's drained the 450mAh 3cell so I hooked my multimeter into the balance plug of the 3cell and fully powered the system up, lights and all. I just didn't throttle up since it was sittin on the floor here in front of me. I ran it for an hour to get sufficient voltage drop on the 3cell to calculate a max run time and I came up with over 3 hours I can run the LED's before the battery is depleted. But like I said it ran for an hour with no apparent issues. I made a monstrosity and fried 1 of the 2 brushed ESC's so the one with a voltage conflict is toast. The brushed ESC only runs true for about 45 seconds then everything go NUTZ! so the brushed ESC cant handle the current draw of the receiver, the gyro, and 5*5g servos BUT I have done up the surface linkages properly now so I'm down to 3 servos on the airframe. I just haven't re-tested it yet.


On a side note:
The monstrosity I speak of was a 2 channel early model flybar helicopter. I removed the receiver it came with, used 2 brushed ESC's to power the main rotor and tail rotor and installed a brushless ESC motor prop combo on the front end. After I fried a brushed ESC I put a brushless motor on the tail. I used the 3axis stabilizer on the tail rotor only as a head lock gyro. I did get it to fly but by the time the gyro and I got the tail to head lock properly the entire unit was sittin at 40 degrees 5 feet off the ground. It's taken hits from this height before so I powered down and this time when it hit the elcheapo early 90's plastic frame all by vaporized on me. LOL I have build videos but not a video of the maiden failure. Think it's worth my time to splice em up and post em on youtube?

EDIT: LOL Brain fart. =p ---|>|--- diode, conflict averted. ^_^

 

[mesolost]

Anyone think about using a SuperCap to help out on peek power draws?