ESC Blowing the bec in a 150amp ESC

[RC MAN]

Hi yall, I havent posted in here in a while.
But now I have a problem I would like to fix, Its on one (or all) of my Dragsters.

The problem is I keep blowing the bec in the escs Im using, If I set the timing and punch way down, it seems to be ok.
If I set it to high, it goes POP on takeoff. So I put a separate ubec in from HK at 3amps, 5amps burst.
The only thing hooked to the ubec is now the rx and the servo, I cut the power wire from the esc and put the ubec on the wire goin to the rx.

Took it out again, tried with lower setting, all ok, just no punch on take off, set the esc at a higher setting, better, but not enough.
Took the settings all the way up, hooked up the batt. switched on the esc, and tried reverse, as it is set for 50% (Ya dont need to go fast in reverse)
All ok, than just a quick punch on the throttle forwards, and the car shut down with the Magic Pop, the ubec fried too.

Specs on the car are as follows,
Esc: Hobbywing 150 amp
Motor: Lrp 4turn Vector
Servo: T2M TS222MG
RX: Spektrum SR300
Batt.: 4000mah 50c
Gearing 3.33:1

I was using 5:1 gearing with good take off, but the topend was poor.
I am going to try a small 2s 500mah batt for the rx, but dont want to fry anything else.
the rx can handle 9volts, the servo 6volts, I tried a 1s batt on the rx, and the servo and rx were ok with that too, but I dont want to
have an out of control missile heading for oblivion. If the batt. gets drained to fast.

I just dont understand why the becs are all cooking on me. If I disconnect the power to the esc, motor power shouldnt have any influence
on the rest of the system?

Frank
Thanks for any help yall.

 

[Tony]

With just the Rx and one servo, you shouldn't be pulling any kind of amps to pop these. Even teh 3a BEC that you had should have handled that power.

My suggestion, get a 150a ESC for your main motor and make sure it does NOT have a BEC built in, otherwise known as an OPTO. Cut or pull the red wire from the plug going into the Rx. Then, order yourself a LiFe battery, which is a max of 6.6 volts and not 7.4 so you don't fly your servo. The servo can handle the 6.6, but the 7.4 will fry it.

Set it up that way and you "shouldn't" have a problem. The only thing I can think of is 1, your ESC with BEC is backflowing voltage and killing the BEC, 2 the same is happening with the little 3a BEC and popping that one too (which is why you should remove the red wire from the ESC plug into the RX).

But again, 150a OPTO ESC, cut the red wire to the Rx, 6.6v LiFe Rx pack for power to the Rx and servos and you should be golden. And "should" is used very lightly here.

 

[RC MAN]

Hi Tony,
Thanks for the quick reply.
I did remove the esc wire from the plug and hooked the ubec wire to that going to the rx, so no power that could go to the rx from the esc.
Thats whats got me stumped. Im just powering the rx and the servo, and Pop goes the bec when I throttle it.
Weird stuff always happens to me.

 

[Tony]

That is truly weird. And with you saying that, I would be worried about putting a LiFe pack on it. Last thing you want is voltage feeding back into that pack, and BOOM, the pack explodes. Now this is far fetched and more than likely not going to happen, and lets face it, HK's bec's are not that great (I had the one that you have/had and wasn't impressed).

The reason I suggest the LiFe pack over a Castle Creations 10a BEC is because it's a separate battery. You are not feeding power from the main pack for the motor. Not only will this put more power to the motor, but in case something does happen, it won't fry all of your electronics. And you can get a LiFe Pack almost anywhere. And they are not that expensive.

 

[RC MAN]

Well, I just tried it on a 1s lipo, Its working, but look what happened now, everything was new on this car.
Kinda makes one want to quit messing with these things.

 

[Tony]

Holy crap, you broke the motor shaft? Wow. Thankfully, you can get just the armature for those motors and don't have to order the whole thing again.

 

[RC MAN]

well, its a X11. from LRP and no one has the arm anymore. I have an X12 3turn with a spec 2 shaft, but it dont fit a x11. Windings are burnt in it.
New motor time I guess.
Im thinking it comes from to hi of a gearing on the motor, 3.3:1 is high, 13000 rpms on the wheel.
I went back to a 22 tooth and the accel was better. Or the motor isnt quite right. could have a short in it, but still run.
Hmmm, so many problems in 1 day for me.

thanks for the Help man.
LOL, First the esc bec, than a external bec, than a motor shaft, LOL My broken parts bin is getting BIGGER...

 

[Tony]

You say the windings are burnt? If so, then this could be the cause of blowing stuff up. I agree, I think it's time for a new motor. Get one that is bigger, if you can, and use a higher gear ratio. Something like 4.5:1 to keep the stress off of the motor and ESC, but still get the ET's that you are looking for. But I know how it is. You get a bigger motor to put less strain on stuff, and you instantly want to go faster hahahahaha. Good luck and keep us posted.

 

[RC MAN]

27 tooth pinion was way to big, my rollout was at 2.6 or so, I forgot to change back, and wrote the wrong calc. on my calculator.
Costed me a bec x 2.
Am going to a 3 turn X12 modified, that will fix the broken shafts as they have better shafts than the stock spec motors.
And I have a 3 turn for parts. My old 1.
I will need to use between 16-19 tooth pinions on it. Think Ill throw away my bigger pinions so I wont burn more up LOL.
But still need them for my Drifters.

Frank