ESC BEC issue, help please

[Josh_Br]

Hello,
I am running a Castle Mamba Max Pro ESC, a Spektrum SR300 Rx, and a Savox servo. When I steer either way, then *quickly* return to neutral steer, the power to the Rx is temporarily lost. The truck is then glitchy for about two seconds, then works fine again.

I have done some trouble shooting. I have tried different servos, and it acts the same; the servo is not the issue. I have tried supplying power to the Rx from a battery and unhooking the ESC, and the problem does not happen. I have tried unhooking the servo from the Rx, then jarring the truck around and steering quickly, and it also does not happen then.

The problem seems to only happen when I steer quickly with all the electronics hooked up like normal. The Rx temporarly looses power coming from the ESC.

Any ideas? Thanks

[Charlie-III]

Without checking the specs of your servo, I will guess that it's ~200inoz or more, thus the "instant" load is overpowering your ESC BEC, this causes a ESC/RX brownout.

If so, an external BEC will cure the issue.

[Josh_Br]

Originally Posted by Charlie-III

Without checking the specs of your servo, I will guess that it's ~200inoz or more, thus the "instant" load is overpowering your ESC BEC, this causes a ESC/RX brownout.

If so, an external BEC will cure the issue.

Yeah the servo is about 280 oz/in. What you said would make sense. Because it does not matter whether the servo is actually hooked up to the steering gear or not. I tried another servo (300+ oz/in), not hooked up to any thing mechanical - just the servo itself - and it behaved the same way.

So long $20......Thanks Charlie for the insight

[Meatwad]

This one is a good read

Yes you need an external bec

You didn't mention the voltage you're running, on 3s its basically mandatory and 2s its somewhat needed depending on the servo and/or torque specs. The Savox servos are inefficient compared to others, not bad servos just draw more current than other servos.

[The Violator]

I say you are fine. Just keep at it, eventually you will prove the entire RCC community wrong by not needing a BEC.

[Josh_Br]

I'm running 2s.

I have a BEC in my other crawler. I put the BEC in the that truck because it still has the stock Axial ESC, which has a 5v output. I wanted 6v output, so I added a BEC.

For the truck that this thread is about, I have a Mamba Max ESC, and you can set the BEC output at 6v, so I was thinking that I didn't need a BEC with this truck. But it seems I'm wrong I am guessing that the amp draw it too great with the high torque ESC, despite the voltage being adequate. Sound right?

Thanks

[SMR 510RR]

CC internal BEC's are crap, I am convinced that they do it on purpose to charge an additional $20 for the damn external one.

[Josh_Br]

Just ordered a CC BEC.....another $20 into the bottomless pit of RC!

[Charlie-III]

Originally Posted by Josh_Br

Just ordered a CC BEC.....another $20 into the bottomless pit of RC!

Yeah......if the servo will handle it & you're running 2S LiPO you could run the servo direct off the battery, thus not needing the external BEC.

While ~200inoz is not carved in stone, it's about the break point for any internal BEC in a ESC. Once you get there, you really need an external BEC.

[Josh_Br]

I have two Savox high torque servos. I like them because they don't cost as much as others, and they're fast. But, the instructions say to run them at 6v max. I'm not sure if they can handle more volts.

I like your 200 oz/in rule. After I posted I tried an Axial servo that's rated at ~150 oz/in, and the problem was not as severe.

Well, when that BEC gets here I'll be in good shape. Thanks!

[Charlie-III]

Originally Posted by Josh_Br

I have two Savox high torque servos. I like them because they don't cost as much as others, and they're fast. But, the instructions say to run them at 6v max. I'm not sure if they can handle more volts.

I like your 200 oz/in rule. After I posted I tried an Axial servo that's rated at ~150 oz/in, and the problem was not as severe.

Well, when that BEC gets here I'll be in good shape. Thanks!

The 200inoz is not really "my" rule, but in general it seems to be about the limit for internal BEC's. Some are better than others (the Holmes Hobbies BR-XL is a decent one) and others are weaker.

The "rule" is from reading enough threads to see ~when people are starting to have issues. It's reasonably close.

As an aside, I NEVER needed an external BEC until I started crawling, all my older ESC's (Novaks BTW.....they work well in my 12th/10th carpet cars & 10th dirt buggies.....) were up to the task of any servo I used. The need for an external BEC is a new one for me.

Hope it works out for you.