Do I need a BEC?

[Kaptnsmooth]

I just purchased my first Balsa 3D plane from a friend. Only thing needed is an ESC and I am set. Question is I keep reading about BEC. I understand what it is for but is that something I really need? I always land my planes with about 45-50% left on battery. If I can go 8 minutes I land at 5. So do I need to purchase a BEC. I have already purchased my ESC and really don't want to have to put a BEC on the plane if its something I may never need. So if you can help me with this decision please help. Thanks in advance!!!!
Rick

[ryramZ]

Re: Do I need a BEC?

Better safe than sorry. I would say yes! 3D PLANES utilize more throw than most which demands more from the power system than just easy breezy sport flying. Another thing is the size of the servos. I don't know what plane you are asking about but if the plane is using bigger than 9 gram servos then I'd say again definitely use a BEC.

[ryramZ]

Re: Do I need a BEC?

http://www.motionrc.com/battery-eliminator-circuits/

[Tom]

Re: Do I need a BEC?

I will throw in my two cents too. I think the question you are asking is, "Do I need an external BEC". Some ESC include a BEC and some do not. If your ESC does not have a built in BEC, you need one. Most include a BEC. Most internal BEC are 5A max. Some planes do require more than 5A to power the receiver, servos, landing gear, and lights. In this case, you would want a larger external BEC (sometimes called a UBEC). If you fly Spectrum, you will need to pay particular attention to this. Our experience tells us Spectrum receivers are more sensitive which results in planes falling out of the sky. Some Spectrum users go as far as adding an external receiver battery pack. When Spectrum gear is setup with a UBEC and external battery pack, you no longer have any brown outs. I don't know what brand receiver you are using but other brands are not as sensitive.

Also, I'm not sure how far you drain your LiPo. You ideally want to check the voltage per cell. I aim for 3.75V to 3.8V per cell when the battery is at rest (checked about 5 min after landing).

[Kaptnsmooth]

Re: Do I need a BEC?

Thanks everyone. You have been a big help. I am going to purchase the castle BEC you guys have here. Going to look to see if there is a adapter I can use to connect to the battery so I don't have to solder extra wires to dean connector. As you can see this is my first at using BEC so I am wanting to make sure I am doing it correctly. I spoke with my friend who sold me the plane and he mentioned the Castle Creations BEC 10A. If you have any other suggestions for me please shoot them my way as I definitely don't want to make a mistake. I do thank you all for your support and thank you Tom for all you do!
Rick

[Kaptnsmooth]

Re: Do I need a BEC?

Also I am using Hitec recievers with this plane. If that makes any difference!!

[Tom]

Re: Do I need a BEC?

I use Hitec receivers and an Aurora 9 for all my stuff too. Unfortunately, there is no way around soldering. The Castle 10A BEC is one of the best but you will have to solder. There is a wiring diagram picture on our Castle 10A BEC web page. As long as you are soldering, I would solder the cable which plugs into the SPC port on the receiver as well. It will solder onto the same T connector with the ESC and BEC wires (in other words, you will have 3 sets of wires soldered to the connector which will plug into your battery. This way you will be powering the receiver directly from the battery, you will get voltage telemetry for the flight pack, you will have a separate BEC, and the ESC will only control the motor. This would likely be a perfect setup.

[Tootall505]

Re: Do I need a BEC?

Don't forget to disable the internal BEC on the ESC when using an external BEC,buy disconnecting the red wire on the throttle plug from the stock ESC. You can check to see if you have it right buy unplugging the throttle plug from the ESC and the servos should still work.

[Tom]

Re: Do I need a BEC?

Good tip. If you don't want to cut a wire or remove it from the housing, this short BEC eliminator cable can be used. It only has the two outside wires.
http://www.motionrc.com/150mm-bec-eliminator-cable/

[retiredflyer]

RE: Do I need a BEC?

I have a quick question.  Just got 3 of the ZTW UBEC 10 amps.  I see from the wiring diagrams on-line and the one that came with it, shows a 3 connector lead going to the receiver.  The connector that is on the UBEC has only 2 leads (BK/RD).  Is that a error in the diagrams?  Unless I'm going totally blind, it sure looks like a three lead connector to me on the diagram!!!
Also, I bought 3 parallel battery to ESC adapters with "T" connectors on each end and now I see I have to solder the UBEC to one end (or get a male "T" connector), to one side.  That will be tough as the UBEC wiring is 22 gauge, and the adapter uses 14 gauge, (like the batteries). HUGE connector with a tiny wire coming out of it!  Oh well.
 I know I have to remove the red lead from the ESC connector too.
  Thanks for any info.....

:(

[WintrSol]

RE: Do I need a BEC?

I have a quick question.  Just got 3 of the ZTW UBEC 10 amps.  I see from the wiring diagrams on-line and the one that came with it, shows a 3 connector lead going to the receiver.  The connector that is on the UBEC has only 2 leads (BK/RD).  Is that a error in the diagrams?  Unless I'm going totally blind, it sure looks like a three lead connector to me on the diagram!!!

Is the connector on the UBEC a three-position connector, but with only 2 wires in it? If so, that's fine, as the UBEC doesn't use, nor does it need, the signal line from the receiver. The photos on the site don't show this connector, unfortunately.

Also, I bought 3 parallel battery to ESC adapters with "T" connectors on each end and now I see I have to solder the UBEC to one end (or get a male "T" connector), to one side.  That will be tough as the UBEC wiring is 22 gauge, and the adapter uses 14 gauge, (like the batteries). HUGE connector with a tiny wire coming out of it!  Oh well.
 I know I have to remove the red lead from the ESC connector too.
  Thanks for any info.....

:(

I assume this is the adapter you bought: http://www.motionrc.com/t-connector-2-to-1-parallel-esc-adapter/. That's actually to use one battery to power 2 ESCs, but you could power your BEC with it. Personally, I would put a T connector on the UBEC, to make it simpler to connect, but you could remove one female T connector, and splice the UBEC wires to the wires.
Personally, I would have gone with this: http://www.motionrc.com/t-connector-pass-through-with-jst/, and put a JST connector on the UBEC.

[retiredflyer]

RE: Do I need a BEC?

I have a quick question.  Just got 3 of the ZTW UBEC 10 amps.  I see from the wiring diagrams on-line and the one that came with it, shows a 3 connector lead going to the receiver.  The connector that is on the UBEC has only 2 leads (BK/RD).  Is that a error in the diagrams?  Unless I'm going totally blind, it sure looks like a three lead connector to me on the diagram!!!

Is the connector on the UBEC a three-position connector, but with only 2 wires in it? If so, that's fine, as the UBEC doesn't use, nor does it need, the signal line from the receiver. The photos on the site don't show this connector, unfortunately.

Also, I bought 3 parallel battery to ESC adapters with "T" connectors on each end and now I see I have to solder the UBEC to one end (or get a male "T" connector), to one side.  That will be tough as the UBEC wiring is 22 gauge, and the adapter uses 14 gauge, (like the batteries). HUGE connector with a tiny wire coming out of it!  Oh well.
 I know I have to remove the red lead from the ESC connector too.
  Thanks for any info.....

:(

I assume this is the adapter you bought: http://www.motionrc.com/t-connector-2-to-1-parallel-esc-adapter/. That's actually to use one battery to power 2 ESCs, but you could power your BEC with it. Personally, I would put a T connector on the UBEC, to make it simpler to connect, but you could remove one female T connector, and splice the UBEC wires to the wires.
Personally, I would have gone with this: http://www.motionrc.com/t-connector-pass-through-with-jst/, and put a JST connector on the UBEC.

Yes, you correct, it is a three position connector only using the black and red spot. Thanks. I didn't realize what size the wires were and the huge difference in sizes so you are right again, I will use your suggestion and get the battery pass through with the JST connector. Much neater and smaller and easier to put the small leads from the UBEC into. Appreciate the info.

[WintrSol]

RE: Do I need a BEC?

In case you haven't thought that far ahead, you should connect the UBEC to the battery before the ESC, so the receiver is running; that way, the motor won't start unexpectedly, assuming the transmitter is also on first.

[retiredflyer]

RE: Do I need a BEC?

In case you haven't thought that far ahead, you should connect the UBEC to the battery before the ESC, so the receiver is running; that way, the motor won't start unexpectedly, assuming the transmitter is also on first.

I actually would not have even thought about that and had the adapter (pass through with jst) always hooked up to the ubec, and the esc already hooked up and just hooked up the battery like usual when I was ready to fly. You're saying I should power up the ubec first, which is now actually powering up the receiver, THEN connect the esc to the battery. The esc is no longer powering the receiver from the battery as before, correct? I didn't care before as the receiver/esc were being powered simultaneously.  I understand what you're saying, thanks, I would NOT have done that at all and might have sliced off a finger. Appreciate your insight into my safety! :)

[WintrSol]

RE: Do I need a BEC?

In case you haven't thought that far ahead, you should connect the UBEC to the battery before the ESC, so the receiver is running; that way, the motor won't start unexpectedly, assuming the transmitter is also on first.

I actually would not have even thought about that and had the adapter (pass through with jst) always hooked up to the ubec, and the esc already hooked up and just hooked up the battery like usual when I was ready to fly. You're saying I should power up the ubec first, which is now actually powering up the receiver, THEN connect the esc to the battery. The esc is no longer powering the receiver from the battery as before, correct? I didn't care before as the receiver/esc were being powered simultaneously.  I understand what you're saying, thanks, I would NOT have done that at all and might have sliced off a finger. Appreciate your insight into my safety! :)

Well, leaving the UBEC and ESC connected, and just connecting/removing the battery would be fine in most cases, since that's how most small electrics work. Just be sure you are clear of the motor-driven parts when doing it this way, in case the ESC misbehaves. Since you have the option, though, it would be just a bit more safe to connect the ESC last, as the receiver would be stable by then. Also, it gives you the chance to do a control and range check, without worrying about the model running away. The worst thing would be to connect the UBEC last. "If it can happen ...", Murphy.

[retiredflyer]

RE: Do I need a BEC?

I'm having a senior moment here. I just hooked up my BEC in my Mustang, and I have it connected to the receiver via a y-connector to the throttle port. I woke up last night and said...no you idiot, it needs to plug into any other spot but that one! It all seems to work fine but should I have connected to a different spot, like gear, or aux? (I'll still need a "Y" because all my spots are taken. The BEC wiring diagram shows AUX so I probably did this wrong. Maybe it doesn't make a difference as long as it gets to the receiver and I cut the red wire on the ESC. Am I correct here?

[WintrSol]

RE: Do I need a BEC?

I'm having a senior moment here. I just hooked up my BEC in my Mustang, and I have it connected to the receiver via a y-connector to the throttle port. I woke up last night and said...no you idiot, it needs to plug into any other spot but that one! It all seems to work fine but should I have connected to a different spot, like gear, or aux? (I'll still need a "Y" because all my spots are taken.  The BEC wiring diagram shows AUX so I probably did this wrong. Maybe it doesn't make a difference as long as it gets to the receiver and I cut the red wire on the ESC. Am I correct here?

The receiver power pins are all connected together with a single copper strip on the circuit board, so it doesn't matter which channel gets the power from the BEC. As long as your ESC doesn't have a BEC, or the red wire is extracted or cut from the connector, you are good. BTW, I use a sharp knife to lift the lock on the ESC connector and extract the pin, just in case I may need it later; just tape it back, so it doesn't short out.

[retiredflyer]

RE: Do I need a BEC?

I'm having a senior moment here. I just hooked up my BEC in my Mustang, and I have it connected to the receiver via a y-connector to the throttle port. I woke up last night and said...no you idiot, it needs to plug into any other spot but that one! It all seems to work fine but should I have connected to a different spot, like gear, or aux? (I'll still need a "Y" because all my spots are taken.  The BEC wiring diagram shows AUX so I probably did this wrong. Maybe it doesn't make a difference as long as it gets to the receiver and I cut the red wire on the ESC. Am I correct here?

The receiver power pins are all connected together with a single copper strip on the circuit board, so it doesn't matter which channel gets the power from the BEC. As long as your ESC doesn't have a BEC, or the red wire is extracted or cut from the connector, you are good. BTW, I use a sharp knife to lift the lock on the ESC connector and extract the pin, just in case I may need it later; just tape it back, so it doesn't short out.

Great, thank you. I was wondering if I did it wrong. Yes, I did the clip trick and popped the red out of the connector and taped it back. Appreciate the response.

[CT]

I am planning on adding a Phoenix hv external ubec to my large edf's, and am also wanting a seperate Rx power supply. I am, running all Phoenix 100 a esc's and Spektrum Rx. Per Marks eralier comments from this thread noting that some Spektrum Tx are very sensitive and more prone to brownouts. The question is if a 2s is sufficient for back up power to the ESC, and how to wire this?
Thx Chris

[WintrSol]

Let's clarify: you want to power the rx with one source, and the servos with a separate HV source? Or, do you want to provide backup rx power, in case the supply from the ESC fails?

Receiver brown-outs are usually due to a sudden current draw by one or more large servos overloading the power source of the rx, causing the Voltage to drop. If you use a separate BEC to power the servos, and the BEC in the ESC to power the receiver (and maybe a servo or three, as it is a 5A BEC), it is unlikely that the 5A source in the ESC will be overloaded, unless you overheat the ESC. If you want to bridge another BEC to the one in the ESC as a backup, you can do this with a couple Schottky diodes, rated about 2X or more the current rating of the BECs, and set the BECs to provide about 0.5V more than you need. Schottky diodes, because of the Voltage-current curve, that improves current sharing between the BECs.

BTW, except for abrupt commands, your flap servos will draw the most current when deployed, because of the steady force on them; same for a speed brake servo. Next in line would be retract servos during operation. When I split power sources for this reason, these are the servos that get a separate source, with the basic elevator, rudder, aileron servos powered with the receiver. That way, I still have basic controls, if the flaps/retracts stall, and load their supply. If you are using parallel servos on the controls of really large models, then you really need to research a power distribution board.