[Boatcrazy]

When if at all should a person use a separate BEC?
Im just getting in to larger electric planes that require 46-60 size electric motors and 6S lipos and have no Idea when a extra BEC comes into play if its already built in to your ESC.
Plus whats the difference between a SBEC and UBEC?
Thanks.

[Mytmerc83]

Derick I use a sbec on anything with digital servos, Anything 3d with big control surfaces. The chance of over powering the bec and losing a plane is not worth it to me. Other can explain it better I'm sure, you would be surprised how many amps a servo can draw especially if it's a big surface or has a bind or rough spot.

[tporter416]

I think UBEC was a brand name, I think they were linear, you want a SBEC since it is switching and can provide more power. Typically the first letter before BEC indicates the method used to convert the battery voltage to the voltage for your electronics.

As for whether or not to use a BEC, I think it is personal preference and what your electronics require. On my large heli I wanted the simplicity of only one battery pack so I use a BEC, some of my fellow fliers find the performance is better and prefer a separate lipo for their 700 sized heli. Servos for large models are very power hungry so make sure you have a BEC that can provide a lot of power if you go that route. My 700 heli's BEC is 10A spiking to 25A if necessary...

Tom

[Max]

You want a separate BEC power supply in case the ESC overloads and poops out, then you lose the motor power AND the radio power.

Anything that uses high current and high loads puts your ESC at risk, especially if your ESC is on the low end.

A classic example is what happened to me this summer. I had and ESC overload on a flight (unknown to me) while flying F3A. The brake was on (didn't know it) and the prop I was using was overloading the ESC on the down-lines of my flight.

Next battery I put in caused the ESC to catch fire. This happened to me on the ground but speaking to the guys at F3AUnlimited, this was a known problem with this particular ESC. In some cases the ESC caught fire IN THE AIR. Having a separate BEC at least allows you to control the model when the ESC craps out. Otherwise, if the BEC and ESC were integrated, the model would have been lost.

The other factor in deciding to use a separate BEC is the size of the model. obviously the large models are more at risk and their value is considerably higher. Dinky foamies and lightweight models may not be at risk as much as their larger and more expensive brethren. For me, anything larger than an equivalent 60 size model (sorry, im old school and my only frame of reference for aircraft size is nitro engine displacement ) would be fitted with a separate BEC.

[tporter416]

To add, a lot of servos can be powered directly from a 2S Lipo these days, which completely removes the BEC requirement, make sure your receiver and any other electronics can run at 8.4V as well. The extra battery adds weight, and you need to make sure it is charged. I have seen a large plane go in due to the separate battery pack running out of juice over the course of the day.

On my large heli I use a BEC as I said, however I also use a BEC gaurd so I can land my heli in case the BEC fails...

https://www.rotorquest.com/index.php...duct_id=108145

I think it is personal preference which way you go, separate battery or BEC, both ways have pluses and minuses...

BEC in ESC:
Pros:
1) Only one battery, flight and electronics run off one pack.
2) Reduced weight
3) Constant voltage to electronics
4) Cost, maybe, ESC's with BEC's aren't that much more, a separate lipo, keeping in good shape will cost you more probably.
5) Most BEC's of that power allow you to specify or select the voltage for your electronics.

Cons:
1) BEC fails, model is going down wherever it is.
2) Power, a BEC is limited to what it can convert, a direct lipo pack can provide a lot more power.

Direct connected 2S lipo:
Pros:
1) Power, a direct connected lipo will provide more power
2) Reliability, less electronics in the way to fail, if the ESC fails or your main pack dies, you have control.

Cons:
1) Weight, will probably weight more
2) Cost, you need another battery
3) Charging, another battery that needs charging and monitoring.
4) Voltage, it will be at 8.4V, then reduced as battery drains. If you need a lower voltage, you need to stick a BEC inbetween your lipo and your electronics.

I hope this helps, I am sure others will add to my Pros/Cons list...

Thanks,

Tom

[Cougar429]

You may also want to check onboard BEC specs. I found most are current limited to far below 5A, so as mentioned, digital servos or high servo counts can quickly overwhelm what it can supply.

Also, an onboard BEC is subject to heating produced by the ESC which surprisingly is higher at part throttle.

Lastly, you will find as the ESC current ratings increase there is less of a chance it will have an onboard BEC due to the noise produced when switching higher motor currents.

Regardless, even my 40A helis and up had separate BEC's and the cost of higher capacity units has dropped drastically. Just remember that the higher efficiency switching BEC's do not like to have power applied if no load on the output end.

Finally, all ESC and BEC ratings are set with a minimum cooling airflow. If in stagnant air, such as buried inside a fuse or other structure, then those can be severely compromised.

[Boatcrazy]

Wow, thanks for all the info guys have learned a lot.

[deaconFlyer]

I would also suggest using a separate BEC on anything that has lights ... particularly LED's ... and/or at a minimum installing a "power filter" (https://hobbyking.com/en_us/l-c-power-filter-0-7a.html) inline if the power is not separate.

While the filters do go a long way to helping a video signal, the amount of electrical noise generated by LED lights can completely hamper the receiver. I would prefer not to put LED's in the same battery as my receiver ... and would never use them without a filter.

For just a few dollars, this is cheap insurance. Quiet power ... quiet plane!

[stegl]

Same old , same old topics and feedback. No mention of brands of ESC as there is night and day between many brands. One must read the specs of each. Statements that are made with one brand may not apply to others.

By starting at the top to made a qualified statement we would have to know aircraft being used , number and type of servos and type of flying. In other words as much details as possible which helps to determine how much draw might be required from the bec. When buying a low end ESC with bec yes they could be combined on the same circuit board and when one quites everything stops. Plus the low end stuff will likely only provide a 3 amp bec at best. Most of your Castle Creations ESC provide 5 amps with some airflow for cooling.

If flying 3D , this would not suffice and you would be looking at maybe a 10 amp external bec and again that depends on how many servos and type of flying. So you see there are a lot of knowns needed before making a selection.

I have been running up to 7 digital with electric retracts and have never had an issue with Castle ESC's providing power but then I scale fly and no 3D. I have overloaded the motor current draw on Castle ESC's to the point where the motor cuts out but the bec keeps working. Just cycle the throttle back to idele and all is reset and ready to go. This was on initial setups when motor draw and ESC were close. I usually either reduced prop size or increased ESC capacity to a higher rating.

Power usage type as stated , will make a difference on whether to use a separate rated bec or not
3D and heli flying definitively have power spikes and so better rated be some should be used.

Some great suggestions here by other posters.