Blowing CC BEC's
 

Absolutely lost on why Im blowing BECs so heres the run down.

Losi CC - Tekin RS w/17.5 - Futaba Fasst - Hitec 7950 - Hitec 225 dig - 3S 20C Lipo.

I was wiring the bec to the battery plug then running it at 6V plugged into the receiver with ESC red wire pulled out. When I roof the truck and pull on the throttle the system dies out. I can see the esc lights blinking and the rx light go red, wait a second and system rearms and can run again.

Also if I put any type of load on the truck the same exact thing happens. Even holding the truck up in the air and pulling the throttle reverse to full will make the esc light drop to red and I lose the bind it seems.

I tried using the bec through the ESC and its only worse, Ill actually lose power to the motor before it dies out.


So I found wiring the bec directly to the servo helped stop it and ran that way for an entire outdoor season. In November I blew my JR9100Z and bec, thats when I got the 7950 and wired a new bec in the same exact way.

A few weeks later I noticed the servo acting weird, like sticking turned then it just up and stopped working. I noticed the green light on the bec wasnt on so i plugged the servo directly into the receiver and it worked.

So I wired in another bec and everything worked again, for atleast a few more weeks. So far I have gone through 4 counting the original with the 9100Z servo.

So I called Castle on monday for some ideas and help. After talking with them about how the bec was wired I had thought I knew the problem. I was connecting the red & black of the servo lead to the red and black of the bec output. Castle said I needed to leave the black wire from both going into the rx, they both needed to be grounded and the rx would do this.

So bec #5 went in the rig and wired up with only the red wires from the servo and the bec connected together.

Went to go practice last night and blew another one. BEC set @ 7.0 ... wired the was Castle told me and same exact thing happened again. Now Im frigin lost ....

I also noticed one other thing last night when using the esc bec. When I wiggle the steering back and forth quickly the servo after a few seconds seems to slow down, you can hear it too, the rx light flickers and if i try to pull the throttle I have like no power to the motor. Once I stop steering and wait a second its like everything is fine until I try to steer some more.

Servo doesnt get hot, not even warm. I have the cap on the ESC, I actually have a bigger 25v cap instead of the 16v Tekin gives ya.

I thought maybe I was pulling past the 20c my packs were rated for so I tried a 25c and a 40c pack. Same results with each pack. I thought maybe I had bad rx's so I tried 2 others and again same results. Then I tried a different servo, hoping but not hoping that was the problem, but again even a simple Hitec 645 seems to draw the power.

Im at a loss ........... anyone ever have something similar? Could a servo, good or bad, cause such a big load on any part of the radio system?

I simply dont know what could be causing the bec's to blow after little use ......

Thoughts .... Ideas ....

??

I think the high torque digital servos are pulling more than 10 amps when we are binding them up. Ive noticed my CC BEC get pretty warm and I only run a 5955 servo, so I can only imagine what the 7950 is pulling from the BEC.

thats what I was wondering and asked the CC guy about too. I under volt my servos so thought possibly doing that was causing it. he said it shoudlnt and the bec should handle it but im skeptical.

I looked at the big CC bec but its like running another esc on the truck. plus it says for best results to run both rx wires plugged in. I only have one bat slot on the 603FF rx and dont know if I could y-connect them together with out a problem.

a friend of mine told me they were having the same problems in their 8scale buggies with the 7.4 servos. they found running the Spektrum bec's fixed it. damn things are 80$ just to try :shock:

anyone ever take a big CC bec apart? how much smaller is it inside?

and can you connect both output plugs together with out backfeeding nay voltage or blowing something up?

banging my head since Im in 2 winter series right now and its already cost me a podium spot at one of them. :evil:

I run the red and black right to the battery plug. I clipped the orange wire off at the BEC. I have a 6" servo extension that the red and brown wire from the BEC are soldered to the female end of the extension (those two wires were pulled out of the male end of the extension. The white wire that goes to the servo is the only wire left in the male end of the extension that plugs into the receiver. I soldered the two servo power wires to the extension because I wanted it to be plug n play if I wanted to change out the servo. Your servo only needs power from the BEC, the function wire (white or orange) from the servo is the only one that needs to go into the receiver. Hope this helps.

Even with under volting your servos, it can still draw too much amperage, especially when the servo is working really hard. I've followed your thread in the LCC section and hate to even ask this, but there isnt any mechanical binding going on is there? I had to clearance the slot on one of my V3 CVDs a touch because it was causing the steering to bind on my truck (even with fresh losi pins and gunnar pins).

I've read this thread a few times and I got nothing, and that's pretty rare. :mrgreen:

But I run HiTec 7950 and 5245 servos straight from the Holmes controller with no external BEC, and on 3S. So something is goofy with your BECs, your RX, your driving, your wiring, or something else.

Back in the day I ran the red and black wire from the CC BEC to the red and black wire from the servo, and only the signal wire plugged into the receiver. I never had a problem like that, and I bet a lot of people do it that way and don't have problems.

Maybe when it comes time to buy the next CC BEC, buy it from somewhere else, maybe the place you got them from got a bad batch or something? They have been known to fail... maybe there was a bad batch? I dunno. See, I got nothing. :mrgreen:

Thats exactly how mine is wired now and I've never had an issue. My ESC powers my RX and dig servo.

Hmmm....usually electricity works such that amps are the inverse of volts.
If you raise the voltage the amps drop, maybe running the lower volts is over amping the BEC causing them to fail?? I would run the BEC output voltage the same as what is required, not setting it lower than required.

How about running a really small 2cell lipo for servo power? If the servo will handle a 2 cell I see nothing wrong with it. Small lipo's weigh little to nothing.

You could have the esc power the rec just like normal.




Randy

I thought the same at first, but I'm sure Hitec would account for this in their circuitry... or at least I hope they would. Their own site list specs for 6v operation and 7.4v operation so they expect it to be operated at different voltages.

I second the bad batch theory. :ror:

could be a bad batch. Ive been doing planes for years and it has been an issue in the past with CC stuff. Contact them and send it in for testing perhaps.

I had a V3 do the same thing last year but fixed that long ago. Ill double check again though, maybe something could have caused it again.


3 RX's same result, my driving sucks and I use your rig for wiring ideas :mrgreen: ......

Same here, always wired my bec's red/red n black/black with no problems. Its like a bad curse that just showed up for me :x


2 of them I got from a Mass store last year, 1 from the same place just last week, 1 from RPP and 1 from my LHS .....

just wired another one in last night that was in my scale truck. plugged it in going through rx and some basement play I could feel it get warm to the touch.


gonna tear the front axles apart tonight and make sure everythings smooth there. I know epa's are good, no humming lock to lock.

appreciate the ideas and help guys ......

Robbob, I have been having a very similar problem with by BEC's lately. I am really starting to think it is the QC at castle or some inferior parts. I have been wiring my BEC's the same for years and never had any problems until lately. In the last 2 months I have had issues with about 4 BEC's. Just about a month ago, Castle replaced one of my bad ones. I wired everything up as usual and it ran perfect for about 1 1/2 months, now it is doing the same thing that yours is. It will work for a while, but then it will cut out all of the sudden. Pause a second or so and it will work again. I can see the green light going out on my BEC, so I have a feeling it is just a matter of time before it goes bad. I talked at length with the Castle guys a couple of times and from all indications, everything I have wired up correctly. Like I said, I have been running it the same for years. My first BEC from Castle lasted almost 2 years before it went out, and I am pretty sure that was because of water. I wish I had more insight, but I am struggling to find the answer just like you.

What servo?

I know of 2 other people locally that have had the same thing happen to them.

2 things in common, both are in LCC's and I wired them ..... cant be me :oops: lol


Front ends coming apart tonight then onto a big boy CC if I cant find anything in there.

I'm stumped on this. Let me mull it over a bit. Any servo heat that you find when you run? Any BEC heat? It sounds like you are having brownout issues, but you have already tried different battery packs.

For the record, it doesn't matter if you wire the BEC directly to the servo or have a common ground at the RX. There is still a common ground at the pack negative lead. As long as you have a ground going from ESC to the RX, all is good.

No servo heat, BEC gets warm to the touch. Not hot but warm enough that you know its doing some work.

You would almost need to get a data logger on it to see what is happening with the voltage and ripple current. Maybe binding in your steering or something. All of this is on just one vehicle, it seems that the only common denominator is the rig itself. You have swapped everything that would matter for this. My bet was on a weak battery, but you probably eliminated that.

I am running a Futaba servo, 9571 I think, if I remember right. I have the BEC set for 6V and I have no heat issues with the servo. No binding in the drivetrain. I checked all that and everything is butter smooth. At first I thought it might be something in the servo, maybe a broken tooth or something, but that is not it. I did have a wire that was almost broken (signal wire), but I fixed that and it is doing the same thing. I also swapped out the servo for a buddy's 8711, but it did the same thing, so I don't think it is a servo issue. Right now I have the BEC powering only the steering servo, with the signal wire coming from the servo to the receiver. The ESC is putting power to the receiver, and the dig servo, but they both work just fine. When it loses power to the steering servo, both the dig servo and the ESC still work fine, so I don't think it is a signal issue with the receiver. Like I said before, I can see the BEC light go out for just a second, so I believe that is the issue. I am going to the LHS tonight to get a new BEC and see if that fixes the issue for right now.

This problem has been driving me nuts for about 2 weeks now. Every time I think I have it figured out, it comes right back at me. I really think it has to be the BEC.

tried 2 20C packs, a 25C pack and 2 40C packs ...... all different brands.

gonna follow up on Killswitch's idea of the front end tonight.