Electronics Setup Information > Setup Info

Run a BEC or not?

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Dogman:
Just bought a used E7SE. Before flying it and trusting the seller that it was 100% I ripped it down. The frame was not level, one of the bearing blocks had stripped screw holes where ca glue was holding the screws in place, there were more mismatched screws then the proper size per the manual, locktite was used sporadically at best, and to top all that off, the smaller gear above the main gear was cracked in 3 spots from over tightening and one of those 2.5x6 flat heads was snapped with ca glue holding it in. Question: It has BK HV servos for cyclic, and MKS HV for tail. They can handle 8.2v, the heli used a 2S lipo direct to the Rx. In my opinion you don't utilize the true potential of the servos unless you run a BEC pro set to 8.2v using a 3S for power. The guy I got this E7 from is against the BEC and says it will crash the heli. I run a BEC pro in my 550x and have no issues. After going over the heli, I really don't his advise holds any weight. What is the true way to utilize the true potential of the 8.2v servo for the ENTIRE flight, not just for the first minute and then servos are running in the nominal 7.4 range of a lipo?

curmudgeon:
First, congratulations on your Synergy E7SE purchase.  It is a well designed and sexy helicopter.

Lets go over a few points.

1) Seller issue:  Unless the seller had warned you about the damaged components, he should take responsibility for these damaged components and compensate you accordingly or even accept the helicopter back for a full refund.  Inspect and scrutinize each component very carefully before rebuilding.

2) HV Servos:  HV servos are generally designed to handle the voltage of a fully charged 2S LiPo.  That is 8.4V.  Your BK and MKS HV servos will handle direct connection to a 2S LiPo without issues.  When I discussed this issue with Tomas (MKS USA distributor), he advised me that exposing HV servos to voltages above 8.0V for the majority of their lives will reduced its potential lifespan.  Using a 2S LiPo does not seem to be an issue as the voltage quickly drops during use to around 7.8 to 7.9V, which seems to be a good compromise between optimal performance without significantly affecting useful life.

3) CC BEC Pro:  That's the same BEC I used on my E7SE.  I powered it with the first 6S LiPo of the flight pack series.  I set the voltage to 7.5v.  I never ran into issues with this setup.  Knowing what I know now, I would have increased the voltage to 7.8v to 7.9v for optimal HV servo performance.  Although I never ran into issues with it, I would also consider using one or two 4.7uF capacitors (or an R2 Buffer Super Capacitor) connected to either the receiver and/or FBL unit empty port(s) for added voltage smoothness.

4) 3S LiPo:  If you are planning on using a separate LiPo to run the electronics, I consider a straight 2S LiPo a more practical option that the 3S LiPo connected to a BEC like you are considering.  One of the main reasons to use a BEC is to eliminate the need for a separate battery.  If you are planning on using a separate battery anyway, you would be defeating the value of a BEC.  If you are intending on using an external BEC, consider connecting it to your main packs.  If using the CC BEC Pro, connect it to the first 6S pack in the series (do not connect it to 12S).  For the ultimate wire neatness, consider using an ESC with a known robust internal BEC like a HobbyWing V4 ESC.

Best wishes on your rebuild.

Dogman:
I was told the heli was 100% and ready to fly. I got it cheap enough where it isn't worth the time to bother with seller. All has been fixed and I set the high low points on esc, and programmed the ar7210 last night. I'm confused about running the BEC off the flight batteries. I run a completely separate power source for electronics on my 550 so if the esc craps out and shorts the flight battery up, I can still auto in, and I like to squeeze every second out of the flight packs bringing them to a safe discharge level, I know it is minimal, but I don't want the servos draining my flight pack. Flight time is a constant discussion, I love to maximize especially now having this E7. As soon as the weather warms up(was 14 for a high yesterday and 18 or 19 today) This E7 is gona be tearing up the skys up here in the mountains of NC. Just wanting the best setup for the best heli I own. Thanks for the reply and info.

quantummodz:
Use a flight pack 2s I had mine on side of frame next to esc area
Then packs should drain at same rate I always leave cables original length on flight packs I found if you make a stick pack with longer leads the rear lipo seemed to have a harder time
I'll try to find a pic to show where I mounted

Sent from my VFD 600 using Tapatalk

Josh Easter:
I run a Bec, Never had any issues.. i would suggest a good Bec like western robotics or i use the castle creations Bec pro with a scorpion backup guard.. just do what works best for you :) Have fun!!

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