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Old Oct 11, 2012, 10:12 AM
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United States, AL, Huntsville
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ok, so now I pretty confused..lol.
I am in the middle a skywalker build and closely have been following this thread. I'm also doing a complete frequency change from 5.8ghz to 1280mhz, which Im very excited about.

I was panning on using 4s for the motor and esc and 3s 11.1 to power my control receiver, the Vrx, Camera and OSD using a bec from that second battery for backup.

So effectively using two batteries. I agree with simplicity, but with 14.8 volt for the motor and esc and everything else being 12 volt, what would be the recommended arrangement then for this?
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Old Oct 11, 2012, 11:19 AM
Cape Cod
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I had asked this very question a few days back. It was discussed in detail in numerous responses in the last few days.

Tom
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Old Oct 11, 2012, 11:49 AM
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Originally Posted by funkmanusa View Post
ok, so now I pretty confused..lol.
I am in the middle a skywalker build and closely have been following this thread. I'm also doing a complete frequency change from 5.8ghz to 1280mhz, which Im very excited about.

I was panning on using 4s for the motor and esc and 3s 11.1 to power my control receiver, the Vrx, Camera and OSD using a bec from that second battery for backup.

So effectively using two batteries. I agree with simplicity, but with 14.8 volt for the motor and esc and everything else being 12 volt, what would be the recommended arrangement then for this?

So can't you use your BEC to step down your 14.8 volts to the 12 you need? What voltage do all the parts in your system need?
Is everything 12, but your receiver, servos, etc, need <6?
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Old Oct 11, 2012, 12:12 PM
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United States, AL, Huntsville
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Ah, so I can use the BEC to step down the voltage? Didnt know it did that, guess thats what the esc would do otherwise(which I understand has a built in BEC).

Yes, only motor and esc on 14.8 volt, video system (Vtx and Camera) is 12 volt, then whatever the control receiver/servos are, I assume 6 volt.. I had bought a 3amp bec, with something like this, would that be too low?



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Originally Posted by Shadrack View Post
So can't you use your BEC to step down your 14.8 volts to the 12 you need? What voltage do all the parts in your system need?
Is everything 12, but your receiver, servos, etc, need <6?
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Old Oct 11, 2012, 12:32 PM
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It'd be fantastic if there is a way I can use my one 4s 5000mah 14.8 battery to power the motor AND all my 12volt stuff.. One battery would be much better.
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Old Oct 11, 2012, 12:37 PM
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Lakewood, Colorado
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Step up or down with this http://www.dpcav.com/xcart/Adjustabl...EPIC-Type.html
combine with http://www.dpcav.com/xcart/Power-Sup...-L-C-Type.html
to keep motor/esc noise out of the FPV side of things.

There are other step-down-only voltage regulators that will supply 12V given a higher input
voltage, that are a little more efficient than the one above, but it's hard to beat this one for
convenience because it'll supply 12V out with any input voltage.

My FPV harness needs both steady 12V and 5V and is run from a 3S battery (which runs anywhere from 12.6 to 9.0V).
See attached.

ian
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Old Oct 11, 2012, 12:38 PM
I tell her RC is cheap !
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Quote:
Originally Posted by funkmanusa View Post
Ah, so I can use the BEC to step down the voltage? Didnt know it did that, guess thats what the esc would do otherwise(which I understand has a built in BEC).

Yes, only motor and esc on 14.8 volt, video system (Vtx and Camera) is 12 volt, then whatever the control receiver/servos are, I assume 6 volt.. I had bought a 3amp bec, with something like this, would that be too low?
In my SW I use a 3S lipo for the motor, and another 3S for video and RC. Video gets the full voltage and the Rx gets 5 volts from a CC BEC 10 amps. Works well.
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Old Oct 11, 2012, 01:21 PM
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Here is my wiring diagram using the immersion equipment.
Reason I went this way is ease, and I get real rssi on my OSD for each of the diversity antenna.
I run into the current sensor with a 3S battery that feeds a current sensor. That feeds power back through an LC Filter to the vTx, which supplies the 5v for the camera.
Also, wired right after the current sensor, is the 10A Castle BEC. that feeds 6v to receivers, autopilot, servos.

The wiring diagram was from my Twinstar so substitute the 2 x 35A Phoenix with 2 brushless motors with 1 x 60A eflite and a 1200kv Orb, and the 2 x turnstile antenna have been switched to 2 x Sander style antenna, 164mm monopoles.
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Old Oct 12, 2012, 07:16 AM
3D Crazy
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Putrajaya, Malaysia
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Originally Posted by erkq View Post
Wellll... not always. 2 magnetos are always good. 2 engines are generally better than 1 if you've got the rating and keep your practice up.
so you add another motor to your SW?

That's interesting! Send some photos dude so we could learn something from you.
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Old Oct 12, 2012, 08:45 AM
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Yeah, enjoy that Twinstar when one motor goes out.
When you are dealing with something that is not concerned with a few ounces of weight, it is a lot different than the planes we are dealing with.
2 batteries are good if they run in parallel and one goes bad, then you have a second source of power.
In the situation we are talking about, either battery goes bad, you are in trouble.
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Old Oct 12, 2012, 10:32 AM
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United States, CA, Sebastopol
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so you add another motor to your SW?

That's interesting! Send some photos dude so we could learn something from you.
Yeah, "dude", and I put 4 magnetos on my unmanned electric hobby craft too. You completely, intentionally missed the point and made wild assumptions about how I implement point-failure avoidance on my unmanned hobby craft. Point-failure analysis and avoidance involves mtbf and calculations.
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Old Oct 12, 2012, 11:14 AM
Crash=start of next project
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The debate on one vs. two batteries will never die. They both work, they both have pros and cons. Study/research and conclude what is right for you. Don't look back until you crash, then make some adjustments.
Some history and help to the new folks is this link http://www.rcgroups.com/forums/showthread.php?t=1309106
Crist Rigotti was one of the early long range SW fliers,17Km.
You say tomatoes i say tomatoe Just keeping it lite, it's a hobby you know.
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Old Oct 12, 2012, 11:23 AM
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Originally Posted by CN I Dawg View Post
The debate on one vs. two batteries will never die. They both work, they both have pros and cons. Study/research and conclude what is right for you. Don't look back until you crash, then make some adjustments.
Some history and help to the new folks is this link http://www.rcgroups.com/forums/showthread.php?t=1309106
Crist Rigotti was one of the early long range SW fliers,17Km.
You say tomatoes i say tomatoe Just keeping it lite, it's a hobby you know.
Yeah... it's all seat-of-the-pants stuff in our arena. Manufacturers don't give us the data we'd need to design a deterministic solution. They probably don't have the data themselves as it would be too expensive to measure and summarize.

When you start putting people or expensive equipment up... that's a different matter. Then they come up with the data.
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Old Oct 12, 2012, 12:07 PM
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Winnipeg
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Seat of the pants is part of the fun, but never knowing if you are going to glitch out all of a sudden, or have your power die and your goggles go black is more stress than I enjoy.
With my TS, I was on the edge of my seat most of the time because if one ESC or motor failed, game over. I would be fine on my RSSI and then all of a sudden link would drop to 50 and in seconds I was getting failsafes.
Adding all the equipment I wanted then increased my stall speed.
Well I forgot to watch my speed making a turn and stalled.
Had my stabilize on, plane goes into a spin from 300 meters up, and doesn't respond.....until I remember to turn off the stabilize, then I can pull out of the spin and get home.
I have had so many BPM's that I should go to the field with a depend on.
Now though, and a lot had to do with reading over 1000 pages of posts, and meeting and talking to the equipment designers from Immersion and Fatshark, that the system I have now is one that I feel safe with for the most part.
I also know how to fly within the limits of the aircraft.
That probably has more to do with my success lately than anything.
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Old Oct 12, 2012, 12:15 PM
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Lakewood, Colorado
Joined Aug 2002
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In my experience (both personal and what I've witnessed watching hundreds of other RC pilots
over the years), batteries don't "just fail" very often. The weak link is invariably human.
Batteries have to be charged and discharged properly, and you've gotta remember to
put a fully charged battery in your aircraft or GS and keep track of how much time you've got
on each battery.. etc.. Have to decide how many flights you can make on one battery
as you swap out others, and adjust accordingly for different types of flights (powered fast
and short or long and slow, or super long soaring with no motor.., cold weather etc).
Even with an OSD to track all that data, it still requires a human to make the right choices,
literally "on the fly".
Manufacturer's published mean time between failure data alone is generally not useful when
looking at the reliable operation of a hobby level aircraft. What is relevant is mean time
between brain fades (MTBBF). How many charge/discharge/flight cycles before you forget
to fully charge a battery, or over discharge one causing damage to it, or choose to store them
fully charged reducing capacity, or just choose to "one last flight" on a battery of unknown
discharge state, and so forth. Generally speaking battery failures are really human failures
and they happen orders of magnitude more frequently than the MTBF of the batteries
themselves or the components you put in the aircraft to replace the batteries (ESCs/BECs
etc).
Thus every battery you add anywhere in the system brings with it the opportunity for a new MTBBF
which is much shorter than the MTBF of the components we use to replace batteries.

If you look at various safety and driver/pilot aids in other systems we interact with regularly,
you can see that quite often the overall complexity of the system is increased
with the express goal, of reducing or eliminating human decision points. For instance, a modern car has
ABS (pulse the brakes to avoid lockup and maintain directional control while threshhold braking),
ASR (traction control, feather the throttle to avoid wheelspin) and
ESP (apply differential braking to simulate countersteering during undesired yaw).
They all do things that humans are capable of doing to greater or lesser degree, but
creating a complex electro-hydro-mechanical system to do it for them, has the net
result of creating a much safer and reliable driving experience.

ian
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Last edited by Daemon; Oct 12, 2012 at 12:35 PM.
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