CC BEC ,design flaw.

[MetalMan]

Three of them have been used in my RCs, one in my rock crawler powering a Hitec 5955TG, one was in my Hyper 8 on 4s pushing an Airtronics 359 and is now in my MT2 on 5s2p A123 with an Airtronics 357, and the last one is in my CRT.5 on 3s with an Airtronics 359. And my SH buggy is using the internal MMM BEC with an Airtronics 359.

[Joe Ford]

Guys, ALL SWITCHING REGULATORS CAN FAIL OPEN...THIS IS THE NATURE OF THE BEAST. If you don't like the idea of that, use a receiver battery.

[BrianG]

Did you mean they can all fail closed? I assumed that the FET S-D terminals shorted (or were driven that way). Anyway, fair enough. It just seems that most other BECs fail by simply stopping to operate.

Knowing that, how hard/expensive would it be to incorporate a voltage switch at the output to cut power if it exceeds a certain value? Since the CCBEC is adjustable to 9v, it would have to be above that...

[Pdelcast]

Originally Posted by BrianG

Did you mean they can all fail closed? I assumed that the FET S-D terminals shorted (or were driven that way). Anyway, fair enough. It just seems that most other BECs fail by simply stopping to operate.

Knowing that, how hard/expensive would it be to incorporate a voltage switch at the output to cut power if it exceeds a certain value? Since the CCBEC is adjustable to 9v, it would have to be above that...

Well, we could use the microprocessor that is on the BEC to determine if the power FET failed, and then use another FET to cut off the output (or use an additional comparator output to drive the FET, and generate the compare voltage with the D/A converter.... etc...)

The issue is that the CCBEC shouldn't be failing -- not with all the over current protections it has. We need to look at the applications to see if we can reproduce the failures in the lab. There shouldn't ever be a failure in a car with only one servo -- people run the CCBEC without any issue on helis and aircraft with 6+ servos.

Patrick

[Arct1k]

I'd add I put 10s (twice) into one of mine (and a MM) and they both survived to tell the tale...

I had a Koolflight BEC fail on me and it took out all my electronics with it. I think it can happen with any BEC.

[GT35R]

Originally Posted by Pdelcast

The issue is that the CCBEC shouldn't be failing -- not with all the over current protections it has. We need to look at the applications to see if we can reproduce the failures in the lab. There shouldn't ever be a failure in a car with only one servo -- people run the CCBEC without any issue on helis and aircraft with 6+ servos.

Patrick

The only reason I got into cars was due to getting bored waiting for the weather to be good for flying. I thought it would be easy (&cheap), I can fly for a year without breaking anything... Not so, the bastards break something every 10min of driving. I guess the electronics don't like being thrown around much either and the conditions I imagine would be hard to replicate in the lab.

Patrick,I threw 1 away but I'm actually pretty close to you so if you want to test the other 1 to see why it failed your more then welcome to it.I need to come in to your shop once you get some MM in anyways.But what I'd like to know is if all these can fail like this,and you know how to fix it,why not do it?BTW 1 of them had only been used with 4s and the other all 4s except 3 times with 6s and a couple with 5s.The 1 I threw away had some slight wire fraying on the receiver wire at the board.Which I couldn't see until I unwrapped it.But it didn't appear like it had been able to short.

[VintageMA]

Originally Posted by asheck

Patrick,I threw 1 away but I'm actually pretty close to you so if you want to test the other 1 to see why it failed your more then welcome to it.I need to come in to your shop once you get some MM in anyways.But what I'd like to know is if all these can fail like this,and you know how to fix it,why not do it?BTW 1 of them had only been used with 4s and the other all 4s except 3 times with 6s and a couple with 5s.The 1 I threw away had some slight wire fraying on the receiver wire at the board.Which I couldn't see until I unwrapped it.But it didn't appear like it had been able to short.

Wouldn't that be nice - living close enough to CC to be able to make personal visits.

Too bad that for the price of the CC BEC most people probably do throw them out rather than sending them in to be checked.

[redshift]

Patrick or Joe, do you want mine?

I bought it from Impakt in May I think, so too late on that one to return it anyway.

And I am using an rx pack so I don't care about an exchange, maybe a coupon for $20 off a Monster?

;)

Can't you just put an appropriately sized zener diode as a shunt across the + and - bec outputs?

[BrianG]

That's called crowbar protection. As long as the BEC output voltage was lower than the zener voltage, things would run fine. If the BEC goes bad and the output voltage goes higher, the zener would basically short out the BEC causing it to either shutdown from overcurrent, burn up, or the zener would blow. Since the CCBEC can output over 7A continuously, you'd need one heck of a zener. Otherwise, as soon as it blew the voltage would go back up to whatever it is outputting. Not really an elegant solution IMO, but certainly simple enough.

[suicideneil]

Please explain, what in theory would that do in an overvoltage situation? (Im getting a headache form this thread...).

EDIT: its like magic....

[BrianG]

Unless the zener was big enough to handle that kind of power, it would blow, and then your receivers and servos would get the full battery voltage again. Crowbar protection is not really the best solution IMO. And if the zener didn't blow, the BEC wires would likely fry.

lol, and there's a similar thread in the Traxxas forums about this very thing.

[What's_nitro?]

Originally Posted by BrianG

Unless the zener was big enough to handle that kind of power, it would blow, and then your receivers and servos would get the full battery voltage again. Crowbar protection is not really the best solution IMO. And if the zener didn't blow, the BEC wires would likely fry.

lol, and there's a similar thread in the Traxxas forums about this very thing.

Just have the zener trigger a larger relay that will handle the current. Or, put a fuse in-line with the CCBEC power leads and put a relay in place to short those leads after the fuse. It will blow the fuse and then the BEC shuts off.