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Old 06-18-2014, 04:01 PM   #1
Davethebluessinger
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Default Best way to power separate BEC?

Just sent for this BEC for use in a Pushycat running a 4S 3700.
http://www.hobbyking.co.uk/hobbyking/store/uh_viewItem.asp?idProduct=29762

It’s major overkill as there are only 2 full sized servos in the plane but it was pretty cheap and I thought it had a built in contingency in case I needed it in the future.
My question is:
What’s the best method of supplying power to this?
Tap into the balance lead on the main LIPO or connect it to dedicated battery pack (was going to use a 3S 800mah I already have).
All advice gratefully received folks!

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Old 06-18-2014, 04:04 PM   #2
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For the most part I wire the bec in to the power plug on the esc that connects to the battery. On one occasion I powered the beck with its own battery.
I prefer not to touch the balance leads.
Seeing as I have to solder a battery connector to my esc anyway it is no big hassle to attach the beck there.
Always check the input voltage rating on the bec before doing this as some cheapy becs cannot handle higher input current.

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Old 06-18-2014, 04:07 PM   #3
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First question what ESC are using ?

Link please.

Then we can tell you what is best way to move on this ... you may not even need the BEC .....

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Old 06-18-2014, 04:10 PM   #4
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I'll Dig out the ESC Details and post later, I think it's a Hobbywing 60A but not sure of exact details....

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Old 06-18-2014, 04:19 PM   #5
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Originally Posted by Wrongway-Feldman View Post
For the most part I wire the bec in to the power plug on the esc that connects to the battery.
^this

You just tap the BEC power supply wires into the ESC input cables, usually soldering them in at the Deans connector (or whatever connector you use). This would be the same regardless of what ESC you are using. You would generally only power the BEC off a seperate battery in high voltage installations where the main flight battery was too high voltage for the BEC to handle.

If the ESC has a built in BEC you must also disconnect the red wire from the plug that goes to the receiver. If the ESC is 'OPTO' (i.e. no BEC) then leave the red wire connected.


As to if you need a seperate BEC or not; that wasnt the question asked so i wont speculate on an answer
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Old 06-18-2014, 04:51 PM   #6
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Originally Posted by Davethebluessinger View Post
I'll Dig out the ESC Details and post later, I think it's a Hobbywing 60A but not sure of exact details....
Contrary I know to your original question How to wire a BEC in ... my reasoning is simple.

KISS.

The Pushycat is not a large or demanding machine in terms of servos etc. It is a medium parkfly ... reasonably fast pusher machine. It has unless modified a couple of 9gr or similar sized servos ... 3 if you separate ailerons.

If you are using a Hobbywing 60A ESC - then unless you have an Opto ESC - then this should work well enough without need for a separate BEC .. and I am well aware that you are going to use a 4S pack.

So if it was me ... I would not bother with a separate BEC if the ESC has a BEC as usually found with Hobbywing ESC's .. which are a good reputable brand. Saves wiring up .. saves a few gr's ..... just makes it that simpler.

But that's me of course ... simple at heart !

If you do want to wire in a BEC ... then you are best soldering to the ESC plug that connects to the battery .. so when you plug in battery it connects to both ESC and BEC together. If the ESC has a BEC built in - then unclip the red lead from the ESC servo lead plug ... you can lift the little plastic tab and pull the pin out. Little bit of tape to hold it out of way and covered.
If it's an Opto ESC - then nothing needs to be done to ESC servo lead.

There is no real advantage with your model to have a separate BEC unless ESC is without inbuilt BEC. Sorry but that's my opinion.

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Old 06-18-2014, 05:16 PM   #7
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Any choice you make has positive and negative points...

Same pack as the motor and you pretty well guarantee that the BEC won't drop the RX off-line due to low supply voltage before the motor won't run. ... if there is no wiring fault. Just one battery to charge so you can't forget to charge the RX pack.

Separate battery for the BEC will keep the RX working if the main power battery falls out of the plane (I've seen that happen)

There are long lists of pros and cons for going either way.

As for where to connect if using the main motor battery to power the BEC... Solder-Y it with the ESC so it shares the same connector. If the ESC is plugged in the BEC is plugged in.
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Old 06-19-2014, 12:43 PM   #8
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Originally Posted by solentlife View Post
... KISS ...
And even KISSER i.e. if you want to use a separate battery:
4NiMH or 2LiFe

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Old 06-19-2014, 10:35 PM   #9
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The ESC is actually a SEEKER GUARD 60A BEC 3A/5V Version 2.1 if that helps!

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Old 06-20-2014, 06:51 AM   #10
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Originally Posted by Davethebluessinger View Post
The ESC is actually a SEEKER GUARD 60A BEC 3A/5V Version 2.1 if that helps!
So - contrary to others - I wouldn't bother with a separate BEC. I'd use the BEC that's in the ESC.

The model has 2 servos ... we are not talking some high-falluting 6 servo 3D job ...

KISS

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Old 06-20-2014, 07:05 AM   #11
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Originally Posted by solentlife View Post
So - contrary to others - I wouldn't bother with a separate BEC.
Nigel,

No one advised that a separate BEC was required

The original question was 'How do i power a BEC?'. That is a simple question and to which was given a simple direct answer. He didn't ask if he needed a BEC, in fact he said that he knew it probably wasn't necessary.

I like analogies....If someone in the street asks you 'what time is it please?' do you tell them the time, or do you start a debate about if they really need to know the time?
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Old 06-20-2014, 08:03 AM   #12
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Originally Posted by JetPlaneFlyer View Post
Nigel,

No one advised that a separate BEC was required

The original question was 'How do i power a BEC?'. That is a simple question and to which was given a simple direct answer. He didn't ask if he needed a BEC, in fact he said that he knew it probably wasn't necessary.

I like analogies....If someone in the street asks you 'what time is it please?' do you tell them the time, or do you start a debate about if they really need to know the time?
Fair enough ... I offered an opinion based on :

OP's post :

"Just sent for this BEC for use in a Pushycat running a 4S 3700.
http://www.hobbyking.co.uk/hobbyking/store/uh_viewItem.asp?idProduct=29762


It’s major overkill as there are only 2 full sized servos in the plane but it was pretty cheap and I thought it had a built in contingency in case I needed it in the future.
My question is:
What’s the best method of supplying power to this?
Tap into the balance lead on the main LIPO or connect it to dedicated battery pack (was going to use a 3S 800mah I already have).
All advice gratefully received folks! "

Basically I take that as .... 'in case I needed it in future' ... well he can keep it for a second model that is more in need than this ... 'all advice gratefully received..' as invitation to voice an opinion.

Secondly that I had made abundantly clear in my first and earlier posts in the thread that I was interested in the ESC used and my possibility to say - use the ESC's BEC.

Third ... I had in post actually also advised how to wire in a BEC separate ... so in fact gave OP two possibilities ... with and without.

So if someone asks about fitting a 33cc gasoline engine to a 25" foam profile model - what would you do ? Give fitting instructions or give opinion that the motor is oversized and not needed ? That it would be easier to fit a xxxx e-motor ?
Yes an extreme example - but only to illustrate my point that the BEC is an unnecessary overkill on a model that flies perfectly well on KISS system of ESC's BEC.



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Old 06-23-2014, 07:22 PM   #13
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Flew it on the BEC in the ESC without hitch. The only reason I mentioned and bought a separate BEC was because I believed that's what the original owner used. Anyhow Many thanks to ALL who posted!

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Old 06-23-2014, 07:53 PM   #14
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Originally Posted by Davethebluessinger View Post
Flew it on the BEC in the ESC without hitch. The only reason I mentioned and bought a separate BEC was because I believed that's what the original owner used. Anyhow Many thanks to ALL who posted!
Great ...

Chuckling as he slides away !!

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Old 06-23-2014, 08:52 PM   #15
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Like i stated already, no one ever said or implied that he needed a seperate BEC. We just answered the question asked which was 'how to wire one'.

FWIW I wouldn't have use a seperate BEC on that model either.
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Old 06-24-2014, 05:26 AM   #16
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Originally Posted by Davethebluessinger View Post
Flew it on the BEC in the ESC without hitch. The only reason I mentioned and bought a separate BEC was because I believed that's what the original owner used. Anyhow Many thanks to ALL who posted!

Just a note here. I'm not certain which ESC brand you're using. But if your ESC doesn't specify it uses a switching type of BEC, I'd be a little careful on running it with a 4S LiPo battery pack. IMHO, if the ESC doesn't specify switching BEC, you almost have to assume it uses a linear type BEC.

Take a look:
http://www.wattflyer.com/forums/showthread.php?t=63779

FYI, if your ESC DOES use a linear BEC, those things can get hot. And if they exceed some 200F, they can shut down, killing power to your receiver and servos. And by the time you get to your crashed model, that BEC has cooled off, and is working again. Yeah, I've seen it happen at our club field several times. As for me, I wouldn't use an ESC with a linear BEC on any model equipped with 3 or more cells in the LiPo battery for power.

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Old 06-24-2014, 06:23 AM   #17
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Originally Posted by kyleservicetech View Post
Just a note here. I'm not certain which ESC brand you're using. But if your ESC doesn't specify it uses a switching type of BEC, I'd be a little careful on running it with a 4S LiPo battery pack. IMHO, if the ESC doesn't specify switching BEC, you almost have to assume it uses a linear type BEC.

Take a look:
http://www.wattflyer.com/forums/showthread.php?t=63779

FYI, if your ESC DOES use a linear BEC, those things can get hot. And if they exceed some 200F, they can shut down, killing power to your receiver and servos. And by the time you get to your crashed model, that BEC has cooled off, and is working again. Yeah, I've seen it happen at our club field several times. As for me, I wouldn't use an ESC with a linear BEC on any model equipped with 3 or more cells in the LiPo battery for power.
Denny ... your advise is always good ... but I think a moment of relaxation is called for here ...

The BEC issue with Linear vs Switching is a known one but IMHO applies more to the low end of ampage ESC BEC.

Many of the lesser power ESC's have low amp BEC in ... some are only 1 or 2A .. that's when the trouble starts.
But many are now carrying 5A ... and they are in the higher power ESC's and I believe that as long as you use an ESC that is S rated well over your requirements - then things should be ok.
The other matter is what and how many servos ... if small analogues - then the issue is less. If larger digitals - then demand can outstrip the BEC .. In fact to be quite honest - outstripping switching as well .. if you are only using 3A .. 5A.

Dave is flying a modell with 2 servos and a high powered ESC ... I think he'll be ok ...

For what it's worth : Listing examples of my models that use ESC's BEC

Edge 540 racer : 2 x ail + rudd + elev - all 4 = 9gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 35A. No probs.

Ultimate EP : 2 x ail + rudd + elev all 4 = 9gr analogue ... ESC BEC and 3S LiPo .. ESC is Hobby King 35A. No probs.

Lanyu 64mm EDF : ail + rudd + 2 x elev, 3 = 9gr, 2 = 4.6gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 60A. No probs.

50mm EDF : ail + rudd + elev, 3 = 9gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 50A. No probs.

Multiplex Twister : 2 x ail + rudd + elev + 2 x Thrust Vector, 6 = 9gr,... ESC BEC and 4S LiPo .. ESC is Hobby King 60A. No probs.

I can go on ... I have various models with 3 .. 4 ... 5 servos ... my F16 is actually only model that I use uBEC on as it has 6 9gr servos on 5S LiPo ...
My Twister in fact had a separate uBEC because of the number of servos at first - when it crashed with a dead uBEC - I tested her with ESC BEC and she passed with flying colours. No matter what load I put on ... it kept going ..

I am not saying we should all go out and throw away uBEC ... far from it ... but what I'm saying is that most applications are fine with them - as long as we stay with reasonable Amp rated BEC's ...
If an ESC is rated for up to 6S and has a BEC - then I would hope that the BEC is not rated at 3S use !!

It would be interesting if we could actually have a manufacturer actually state what S rating the labeled BEC refers to ... So far all I see is odd posts where people calculate reduction of amp as S goes up. Assuming the stated amps are at the lower S rating.

Nigel

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Old 06-24-2014, 05:12 PM   #18
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Originally Posted by solentlife View Post
Denny ... your advise is always good ... but I think a moment of relaxation is called for here ...

The BEC issue with Linear vs Switching is a known one but IMHO applies more to the low end of ampage ESC BEC.

Many of the lesser power ESC's have low amp BEC in ... some are only 1 or 2A .. that's when the trouble starts.
But many are now carrying 5A ... and they are in the higher power ESC's and I believe that as long as you use an ESC that is S rated well over your requirements - then things should be ok.
The other matter is what and how many servos ... if small analogues - then the issue is less. If larger digitals - then demand can outstrip the BEC .. In fact to be quite honest - outstripping switching as well .. if you are only using 3A .. 5A.

Dave is flying a modell with 2 servos and a high powered ESC ... I think he'll be ok ...

For what it's worth : Listing examples of my models that use ESC's BEC

Edge 540 racer : 2 x ail + rudd + elev - all 4 = 9gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 35A. No probs.

Ultimate EP : 2 x ail + rudd + elev all 4 = 9gr analogue ... ESC BEC and 3S LiPo .. ESC is Hobby King 35A. No probs.

Lanyu 64mm EDF : ail + rudd + 2 x elev, 3 = 9gr, 2 = 4.6gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 60A. No probs.

50mm EDF : ail + rudd + elev, 3 = 9gr analogue ... ESC BEC and 4S LiPo .. ESC is Hobby King 50A. No probs.

Multiplex Twister : 2 x ail + rudd + elev + 2 x Thrust Vector, 6 = 9gr,... ESC BEC and 4S LiPo .. ESC is Hobby King 60A. No probs.

I can go on ... I have various models with 3 .. 4 ... 5 servos ... my F16 is actually only model that I use uBEC on as it has 6 9gr servos on 5S LiPo ...
My Twister in fact had a separate uBEC because of the number of servos at first - when it crashed with a dead uBEC - I tested her with ESC BEC and she passed with flying colours. No matter what load I put on ... it kept going ..

I am not saying we should all go out and throw away uBEC ... far from it ... but what I'm saying is that most applications are fine with them - as long as we stay with reasonable Amp rated BEC's ...
If an ESC is rated for up to 6S and has a BEC - then I would hope that the BEC is not rated at 3S use !!

It would be interesting if we could actually have a manufacturer actually state what S rating the labeled BEC refers to ... So far all I see is odd posts where people calculate reduction of amp as S goes up. Assuming the stated amps are at the lower S rating.

Nigel
Hi Nigel
I looked at a couple of your 50 Amp ESC's. They state they are SBEC's which is a switching mode type of BEC, NOT a linear type BEC. The SBEC and uBEC are both switching mode type of BECs.
http://www.hobbyking.com/hobbyking/s...hless_ESC.html

The Hobby King 35 Amp ESC with a 2 Amp BEC is a linear type unit.
http://www.hobbyking.com/hobbyking/s...ontroller.html

As a comparison, the Castle Creations Talon line specifies a continuous current rating for their BEC's. That rating is five amps continuous for the Talon 35 Amp ESC.
http://www.castlecreations.com/products/talon.html
I've got a Talon 90 that has a 9 ampere continuous BEC current rating, and a 20 Amp momentary rating.

Let's assume we actually have a linear 5 Amp BEC running on 4 LiPo batteries. A quick calculation will show that the linear regulator has to handle 4 cells times 3.5 Volts per cell (Minus the 5 volt DC Output) times 5 Amps, or 45 watts. A 50 watt power resistor is about 4 inches long, and a half inch in diameter. Running that resistor at 50 watts will result in about 300 F temperature on the resistor. So, running 45 watts through a tiny 5 volt regulator chip will turn it red hot in a split second.

As for the Hobby King 35 Amp unit, running that unit on 4 LiPo cells, and pulling 2 Amps, the regulator has to eliminate 18 Watts of pure heat. Pulling 2 amps continuously through a tiny un-heatsinked 5 volt regulator will shut it down quickly. The only reason it works at all is that typical servo loads are intermittent. Taking a 48 inch 3D model, and flying it in 3D mode, you might be pulling a fair amount of current through that regulator. Especially with those big wing/rudder/elevator surfaces, and the wild swinging of all three during 3D flying.

Nowdays you can buy the parts for a switch mode BEC for a dollar or three, so a lot of the quality ESC's are going to them. You just got to make certain your particular ESC is using a uBEC or SBEC for receiver power, especially if your model uses more than two LiPo cells in the motor battery pack.

Used appropriately, a linear voltage regulator is extremely reliable. But, to handle their name plate current/voltage specs, they require bolting to a big finned aluminum heat sink, on the order of 2 inches by 2 inches by one inch in physical size. There is more to go wrong with a switch mode type of BEC, but these units are used everywhere, from cell phone chargers powered by 120 VAC or 12 VDC, computer power supplies, computer monitors, televisions, radios, clocks, you name it.

DennyV
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