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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Saw something the other day
08-09-2012 02:15 AM  6 years agoPost 1
Skytrek

rrApprentice

Suffolk, Va

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I saw a 12s setup on a scale bird and the guy was using 2cells through the balance tabs to power the receiver. He was using a regulator and all looked functionally correct.

I was wondering if anyone else has tried this? Pros-Cons? Would you be risking a scale project to save weight? Would there be balancing issues?

Might be a good idea?

Barry London

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08-09-2012 03:07 AM  6 years agoPost 2
Mojave

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Palos Verdes, Ca. USA

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I don't think it's an issue, since the lipo is wired in series. The individual cells will most likely balance as the power is consumed. He probably did it this way so he wouldn't have to wire each lipo with it's own dedicated connector tapped off the main leads. I'm a big fan of stand alone RX power sources, not using the main lipo for power to the RX. This way if you have a bad cell, or the ESC goes poof, you still maintain control of the heli.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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08-09-2012 12:02 PM  6 years agoPost 3
Hokie_Steve

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Virginia Beach, VA - USA

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Hey Skytrek,
Don't think I'd try it. It will unbalance the cells. The two cells would be using the series current of the the motor system the same as the other cells PLUS the added current of the radio equipment that the other cells don't see which will throw the balance out of whack. Although the radio doesn't require near as much current as the motor, there will be a difference in the amount of power consumed. You'd be better off running a regulator off of all the cells so they will drain equally because they will all be seeing the same current. Either that or use a separate pack. Otherwise, the two cells you are using will require an extra 350 mAh or so after every flight to rebalance. You'd have to shorten the flights to avoid over draining those two cells and I would say charging would take forever because of the extra balancing time, not to mention probably shortening the life of the packs. I'd draw you a little picture of the circuit you are talking about to show you why this is but it's a pain in the butt on here. I'll draw it up on a Hardee's bag at Debbies
Steve

Fury 55, N5, Rave N FBL, Aurora, Furion 450

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08-09-2012 12:28 PM  6 years agoPost 4
Copter Doctor

rrProfessor

Enterprise/ft.rucker ,al- home of army aviation

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I'm a big fan of stand alone RX power sources, not using the main lipo for power to the RX. This way if you have a bad cell, or the ESC goes poof, you still maintain control of the heli
Amen!!

drive a rotary, fly a rotorcraft

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08-09-2012 02:07 PM  6 years agoPost 5
doorman

rrProfessor

Sherwood, Arkansas

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Mix
I use a mix of both ways.. power from one pack of the mains in a 12s system, and an onboard battery alone for the airborne equipment..
All of my scale machines have the separate pack...on pod and boomers, I tap off only one of the batteries, as Mojave mentioned.. the difference in the power usage is negliable, and does not cause any problems charging, discharging, or balancing...
The reason to tap off only one is to use a lower voltage to the regulator...cuts the heat way down too...

Good Luck, Stan

AMA 2918-Team Spin Blades,,Castle Creations, Unique Aircraft

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08-09-2012 02:54 PM  6 years agoPost 6
coptercptn

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Mesa AZ. USA

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I like the security of running a separate rx pack.... Never had a problem.... don't ever want to. And with scalers, the weight is never an issue....

Home of the "Sea Cobra".....

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08-09-2012 04:56 PM  6 years agoPost 7
Skytrek

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Suffolk, Va

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Yep,,

Many great points. I also use a receiver pack on all my electric helis but one that is tapped off one main battery and regulated. I thought it was a cool idea when I saw it but the loss in security pointed out ain't wroth the risk to me.

Maybe on a pod and boom running high voltage stuff where you could lose the regulator and receiver pack altogether. That would be some serious weight savings. Heck your flipping and slamming all over anyhow why not take another risk.

We have a guy that fly's with us who somehow saves his bird no matter what the issue is. Sideways, Inverted, Power loss, stripped gear and still lands on the skids with no damage. All I need is a canopy nut to fall off and I forget how to fly!

Barry London

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08-10-2012 02:05 AM  6 years agoPost 8
JoeDiamond

rrNovice

Chicago, IL

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+1 on the separate receiver pack. Had a friend who lost power to his Trex 600E due to a bad solder joint on the flight battery. He had a separate receiver battery and was able to auto it down. Without the receiver battery it would have become a flying (falling?) brick.

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08-10-2012 02:28 AM  6 years agoPost 9
JKos

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Redondo Beach, CA

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> due to a bad solder joint on the flight battery.

And bad solder joints never happen in receiver battery packs? Hah. That's misplaced trust.

I would think your radio gear setup (servo's, etc.) would be part of whether splitting is good idea or not. That being said, I know guys who fly hard core 3D that split their power from 6S out of 12S and it works just fine for them. It has been a non-issue, really.

- John

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08-10-2012 03:39 AM  6 years agoPost 10
Mojave

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Palos Verdes, Ca. USA

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Yeah, but how often do you see a cold solder joint in both the flight pack and the RX pack at the same time?? At least he was able to auto the heli to a safe landing. I'll take my chances with a seperate RX lipo. If you want to really cover your bases, just run the BEC off the ESC and a redundant seperate regulated power supply to the RX from a 2S lipo. Just make sure that they are both supplying the same voltage and you are good to go. You can never be too safe when you're flying a fully detailed scaler. Fixing a fish head is no big deal, just replace broken parts...
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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08-10-2012 03:42 AM  6 years agoPost 11
Skytrek

rrApprentice

Suffolk, Va

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(((FISH HEAD)))

New one on me,,,,I like that!

Barry London

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08-10-2012 04:18 AM  6 years agoPost 12
JKos

rrProfessor

Redondo Beach, CA

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Mojave,
Redundancy is even better, indeed. They don't even have to be the exact same voltage if you use an isolator. I admit, if I had a scaler I would be looking for redundancy.

- John

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08-10-2012 05:47 AM  6 years agoPost 13
qroadrunner96

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Birmingham, AL

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12S and 2S
I personally like to run my birds with the 2S Lipo's because of the security it provides....as I run HV setup without issue, I get 6 minutes of mild 3d and batteries come down at about 3.82/cell and I get about 6 to 8 flights out of my 2S's RX packs the weight is not an issue as having control of the bird if a cell dies means more then 147g's of weight, my bird fly amazing and I love it my ESC, Motor and Batteries run barely warm(spider packs) 1800 1900 and 2050 HS. My logs show my highest temperature was 149F The HV setup uses almost no amps therefore the draw is very small.. works great for me.

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08-10-2012 02:35 PM  6 years agoPost 14
coptercptn

rrElite Veteran

Mesa AZ. USA

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I use Life packs (Usually unregulated),2S,4600mils.. they carry a steady 6.6v and I can charge them in the bird with no issues.

Home of the "Sea Cobra".....

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10-09-2012 08:46 AM  6 years agoPost 15
95nostalgia

rrApprentice

US of A

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Redundancy
I run a 2s 5000mah Lipo thru a Western Robotics BEC to the RX & Stab circuit. Then 12s dedicated to the ESC/Motor only. Typically 10min flights (60-70% batt usage) and 6 flights from the 2s (50% batt usage) over the past year. Nothing is even warm except the Scorpion/Boca motor which has max'd at approx 140F on a hot Texas day.

Not certain this is really true redundancy though. As mentioned before, a failure of one circuit is a failure. Redundancy is having TWO sources for one circuit. Even then, somewhere each circuit will becomes one. Ask me...being careful to do clean, solid work is sometimes worth more than adding equipment.

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