Solved esc with bec or external bec?

[Headbang]

After trying 6 servos to add flaps to a mustang, I got to build another plane after all the servos locked up as I hit the flap switch. I did quiz FT store about the 35 amp ESC / 3 amp BEC and the number of servos I will post there answer below, It might work, it might not.

---------------------------------------------------

Thank you for reaching out. I am sorry to hear you have had issues getting it to function correctly. We do recommend 4-5 servos as this was a problem that was encountered. You can do 6 but you will have to use a secondary BEC. You may need to add something like this: https://www.amainhobbies.com/castle-creations-10-amp-adjustable-bec-cse010-0004-00/p18210

It sounds like the servos are just barely wanting to pull too much power. I look forward to hearing back from you. Have a great day!

Ticket: https://support.amainhobbies.com/helpdesk/tickets/104109

Best Regards,

Kyle F.
Customer Service Specialist

6 servos you need a separate bec. Castle 10amp bec's are what I use on all of my smaller planes with lots of servos. They are cheap and just work. With out it you could have symptoms like reciever rebooting, servos randomly doing crazy things, servos just not working. My seaduck with 7 servos does not work without a separate 10amp bec.
With flight test 9 gram servos you need to think 0.75amps per servo to be safe. Other brands will have power draw specs available.

 

[Sero]

I think most questions have been covered here. But I'll throw in my 2 cents.

The emax 2215 can handle 4s, my expierince is it actually runs cooler on 4S. On 3s my amp tests show about 26 amps with a 10x45 prop and close to 30 on 4s and 9X4.5 prop. Those are static tests and flying amps usually are lower. I flew my Seaduck on 4s with the amp meter connected and the max amps drawn was 50 amps, so a reduction of 5 amps per motor (30 amps static, 25 amps flying per motor) Keep in mind air density ( temperature, altitude etc) will affect the amperage as well as prop design, so results will vary.

When your running a dual motor set-up its usually recommended to pull the red lead of the ESCs so only one BEC is powering your receiver. But if your using 2 exactly the same ESCS and they use a linear BEC rather than a switching BEC then you don't need to. The Emax 20 and 30 amp BEC's are linear. I'm using the 30 amp Emax ESC's on my Sea duck and didn't pull any of the red wires which would bring the BEC supply amps to 4 (2amps each ESC). I have 5 servos on my Duck (flaps) and that's too much for 2 amps. Generally ESCs that run linear BECs are only rated up to 4s, if the ESC is rated higher than 4s it will be a switching BEC. Best to always to look at the specs to be sure.
General rule I follow is that analog 9 gram servos will pull about 0.5 amp near stall usually half that under normal use. Digital servos will use twice that.
Don't forget he receiver! They usually pull 0.25 amps but I usually calculate them inat 0.5 amps.
Also keep in mind that servos use the most amps while moving and very little at idle and not all planes you will be using all the servos at once, so if your very active with the sticks, such as on a 3D plane, err on the high end side.
This is based on research that I've done, not actual testing.

 

[moret]

I think most questions have been covered here. But I'll throw in my 2 cents

Also keep in mind that servos use the most amps while moving and very little at idle and not all planes you will be using all the servos at once, so if your very active with the sticks, such as on a 3D plane, err on the high end side.
This is based on research that I've done, not actual testing.

What happen to my mustang, First battery did ok, dropping flaps after I was lined up to land, or up before turning away from the runway. Switch flaps halfway at a time.

Next battery. in the middle of a hard left climb out, I flipped the switch from full down to full up. And the Plane came full down, hard! All the servos locked at the end of their range. I did not get the throttle cut before it hit the ground. Another trip to Dollar Tree

 

[JennyC6]

6 servos you need a separate bec. Castle 10amp bec's are what I use on all of my smaller planes with lots of servos. They are cheap and just work. With out it you could have symptoms like reciever rebooting, servos randomly doing crazy things, servos just not working. My seaduck with 7 servos does not work without a separate 10amp bec.
With flight test 9 gram servos you need to think 0.75amps per servo to be safe. Other brands will have power draw specs available.

I find it hard to believe they're pulling 5 watts through those absolutely microscopic wires they have. I have had to repair several of my FT 9g servos because the angel hair conductors just pull out of the crimped contacts inside the plugs if you so much as grimace menacingly at them. Probably my biggest complaint about the servos. Absolutely tiny wires; 28AWG, 30AWG, I use thicker wiring when I put an LED in an N-scale steam locomotive.

 

[JennyC6]

I think most questions have been covered here. But I'll throw in my 2 cents.

The emax 2215 can handle 4s, my expierince is it actually runs cooler on 4S. On 3s my amp tests show about 26 amps with a 10x45 prop and close to 30 on 4s and 9X4.5 prop. Those are static tests and flying amps usually are lower. I flew my Seaduck on 4s with the amp meter connected and the max amps drawn was 50 amps, so a reduction of 5 amps per motor (30 amps static, 25 amps flying per motor) Keep in mind air density ( temperature, altitude etc) will affect the amperage as well as prop design, so results will vary.

When your running a dual motor set-up its usually recommended to pull the red lead of the ESCs so only one BEC is powering your receiver. But if your using 2 exactly the same ESCS and they use a linear BEC rather than a switching BEC then you don't need to. The Emax 20 and 30 amp BEC's are linear. I'm using the 30 amp Emax ESC's on my Sea duck and didn't pull any of the red wires which would bring the BEC supply amps to 4 (2amps each ESC). I have 5 servos on my Duck (flaps) and that's too much for 2 amps. Generally ESCs that run linear BECs are only rated up to 4s, if the ESC is rated higher than 4s it will be a switching BEC. Best to always to look at the specs to be sure.
General rule I follow is that analog 9 gram servos will pull about 0.5 amp near stall usually half that under normal use. Digital servos will use twice that.
Don't forget he receiver! They usually pull 0.25 amps but I usually calculate them inat 0.5 amps.
Also keep in mind that servos use the most amps while moving and very little at idle and not all planes you will be using all the servos at once, so if your very active with the sticks, such as on a 3D plane, err on the high end side.
This is based on research that I've done, not actual testing.

Putting a zener diode series with the hot line of each BEC would let you use any BEC you want in tandem with any other BEC you want. The zener diode has minimal VDrop in forward bias and acceptable characteristics when reverse-biased to keep one BEC from popping another if it gets slightly stronger.

IMHO these ESCs should have a zener diode on the PCB for this very reason right off the factory floor. They know we're gonna use them in multi-engine aircraft and it'd be super convenient if we could just jam them all into our receivers without having to worry about one BEC smoking another mid-flight.

 

[Headbang]

I find it hard to believe they're pulling 5 watts through those absolutely microscopic wires they have. I have had to repair several of my FT 9g servos because the angel hair conductors just pull out of the crimped contacts inside the plugs if you so much as grimace menacingly at them. Probably my biggest complaint about the servos. Absolutely tiny wires; 28AWG, 30AWG, I use thicker wiring when I put an LED in an N-scale steam locomotive.

Not 5W. 3.75W max 5v*0.75A. No issue for even 30 guage wire at such short distances.

 

[JennyC6]

Not 5W. 3.75W max 5v*0.75A. No issue for even 30 guage wire at such short distances.

I'm running mine off a 2s LiFE that has a nominal voltage of 6.6 and can spike up to 7v when absolutely fully brimmed. At 6.6v the wattage is 4.95, on a fully charged Rx pack they're probably pulling 5.1-5.2 but the numbers I ran are on nominal voltage for 2s LiFE.

 

[Headbang]

I'm running mine off a 2s LiFE that has a nominal voltage of 6.6 and can spike up to 7v when absolutely fully brimmed. At 6.6v the wattage is 4.95, on a fully charged Rx pack they're probably pulling 5.1-5.2 but the numbers I ran are on nominal voltage for 2s LiFE.

I did a test and stalled out a std 9g flite test servo on a fully charged 2s battery @ 8.4v. Went up to 1.2amps before smoke poured out of the servo. Wires did not get hot.
I have smoked 2 9g servos on the bench under normal operation while setting up planes on 2s 8.4v. Near as I can tell from experience, these servos are not designed at all for anything above 6v. LiFe packs are most likely pushing the edge of the limits and should be run with a bec set to no more then 6v.

 

[JennyC6]

I did a test and stalled out a std 9g flite test servo on a fully charged 2s battery @ 8.4v. Went up to 1.2amps before smoke poured out of the servo. Wires did not get hot.
I have smoked 2 9g servos on the bench under normal operation while setting up planes on 2s 8.4v. Near as I can tell from experience, these servos are not designed at all for anything above 6v. LiFe packs are most likely pushing the edge of the limits and should be run with a bec set to no more then 6v.

There's always wiggle room as far as maxes go. 8.4v is a bit extreme...you'd smoke a venerable S3004 if you ran it at that too...whole draw about LiFE is that their nominal voltage range is the same as a 5s NiCd/NiMH pack. Actually slightly lower IIRC. Why us ICE nuts use them so much. Generally any servos, receivers, et-al rated for 5-6v BECs will work fine p.much indefinitely on a 2s LiFE.


What doesn't like 2s LiFE is those linear Spektrum servos what get put on the UMX ultra-micros. I have a couple and one's completely hoop-a-jooped because of a bench test on a half-dead LiFE pack. They're only rated 4.2v MAX.

 

[The Hangar]

Thanks for all the responses guys! Once my build is ready for electronics, I’m going too add my second esc using the tips you gave me. If I’m having issues, I’ll reach out! Thanks!

 

[Sero]

What happen to my mustang, First battery did ok, dropping flaps after I was lined up to land, or up before turning away from the runway. Switch flaps halfway at a time.

Next battery. in the middle of a hard left climb out, I flipped the switch from full down to full up. And the Plane came full down, hard! All the servos locked at the end of their range. I did not get the throttle cut before it hit the ground. Another trip to Dollar Tree

So when you went to get your plane all the servos were at jammed at their end and not getting power?

I've read many times and have done it myself (reluctantly) that people have used 6 servos with a 2 amp BEC, If all the servos, their linkages and control surfaces move freely then the servo shouldn't draw much power. Its when the servo has to overcome resistance is when it will draw the most power.
Also keep in mind that all electric motors will have a small spike of amp draw on start-up. If your transmitter has a way to slow your flaps down it is actually cycling the flap servos off and on multiple times when you flip the flap switch to slow them down. That will cause multiple amp draw spikes that could put excessive load on the BEC.

 

[Sero]

Putting a zener diode series with the hot line of each BEC would let you use any BEC you want in tandem with any other BEC you want. The zener diode has minimal VDrop in forward bias and acceptable characteristics when reverse-biased to keep one BEC from popping another if it gets slightly stronger.

IMHO these ESCs should have a zener diode on the PCB for this very reason right off the factory floor. They know we're gonna use them in multi-engine aircraft and it'd be super convenient if we could just jam them all into our receivers without having to worry about one BEC smoking another mid-flight.

I like this! Thanks for sharing.

 

[Headbang]

Putting a zener diode series with the hot line of each BEC would let you use any BEC you want in tandem with any other BEC you want. The zener diode has minimal VDrop in forward bias and acceptable characteristics when reverse-biased to keep one BEC from popping another if it gets slightly stronger.

IMHO these ESCs should have a zener diode on the PCB for this very reason right off the factory floor. They know we're gonna use them in multi-engine aircraft and it'd be super convenient if we could just jam them all into our receivers without having to worry about one BEC smoking another mid-flight.

Missed this earlier. I do this with my giant scale to run 2 20amp bec's. Total draw can be upwards of 30amps, and rx batteries are a pita on an electric aircraft.

 

[Sero]

Decided to do my own testing. Let me know if you feel I missed something.

 

[The Hangar]

With my bushwacker build I have flaps like the timber x and that thing is maxing out the bec on my $5 esc without even using throttle. Will this turnigy plush 40 amp esc with a 5 amp bec be good enough? I don’t have any open ports in my receiver (except bind) so I don’t think that I can easily use a bec unless maybe I use a y cable on one of the channels. To my understanding you plug the bec into one of the ports other than throttle and either power it from the same battery or another battery so it goes directly to the servos. Is that correct?
Thanks!

 

[The Hangar]

These are the specs of my servos if it helps.

 

[Wildthing]

With my bushwacker build I have flaps like the timber x and that thing is maxing out the bec on my $5 esc without even using throttle. Will this turnigy plush 40 amp esc with a 5 amp bec be good enough? I don’t have any open ports in my receiver (except bind) so I don’t think that I can easily use a bec unless maybe I use a y cable on one of the channels. To my understanding you plug the bec into one of the ports other than throttle and either power it from the same battery or another battery so it goes directly to the servos. Is that correct?
Thanks!

The external bec you can plug into any port including a Y off of another channel and the bind plug one should work too. That bec is going to feed your rx and servos, the esc you will want to pull the red (power) wire out of the socket so that the only juice going to the rx is from your new ext bec.
Now your Turnigy esc you say is 5amps , it should do just fine on it's own . Most of these small servos pull about .06A each. Most esc's only have a 2 or 3A bec built in, not 5A .

 

[chrisvdv]

In a project I’m working on I may end up needing 4s power. I plan on flying it on the old emax 2215 c pack on 3s, but if that doesn’t cut it, I may need to move to 4s power. However, the old c pack motor (and the esc I’m using) are not 4s rated, but my stock power pack b is technically 4s capable. I can’t seem to find a good amp draw chart for it, but I’m skeptical that my emax 20 amp esc will be able to handle the 4s power and 9x6 propeller... The sites I looked at did recommend an 18 amp esc, so I think that it might be OK... what do you think - have you ever flown the stock old emax power pack b on 4s? I just want to make sure this is ok before I ruin all my gear😂. Thanks!

This:
http://www.yinyanmodel.com/En/ProductView.asp?ID=184

 

[K3V0]

This is an educational thread! I’m still green at figuring out electronic layouts beyond the basic 4 channel setup but it seems like bottom line, If I want to make a plane like the bushwhacker or ft legacy or sea duck or anything with more than 4 servos I should be putting in at least a 5 amp BEC. Is that true? I’m asking for guidance and clarification because there are cyber Monday deals to be had and planes to build😄

 

[The Hangar]

This is an educational thread! I’m still green at figuring out electronic layouts beyond the basic 4 channel setup but it seems like bottom line, If I want to make a plane like the bushwhacker or ft legacy or sea duck or anything with more than 4 servos I should be putting in at least a 5 amp BEC. Is that true? I’m asking for guidance and clarification because there are cyber Monday deals to be had and planes to build😄

Yes, that’s recommended, although @Wildthing said most esc’s have only a 2-3 amp bec so a 5 amp bec on the esc would be able to handle the load. Now say you were doing a bomb drop with a bomb on either wing. I wouldn’t worry about adding a bec since each of those servos is going to be pulling juice once, and most likely the other servos will be doing very little as you make a low pass to release the bombs. If you were trying to try some advanced 3-D moves while dropping them, that would be a different story. So if you want to be extra safe, an external esc is good, but not essential for most projects. Even @BATTLEAXE built his bushwacker without an external bec and has had no issues. Since I am doubling my inner flaps as flapperons, I have 6 servos going pretty much constantly, which does create some problems. 😀