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ESC Backup In Case of ESC Failure???

Discussion in 'Electronics' started by HeliDinoRC, Feb 19, 2014.

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  1. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    Electronics is not my stong point and I need a little advice/help......apologies if this has been answered or in the wrong section.

    I am running a 12s system with CC Edge 120HV ESC and a WR Hercules Super BEC G2. The ESC does not have an internal BEC. I bought a Scorpion Backup Gaurd in case of ESC failure; however, apparently I didn't research the application thoroghly and it will not power HV servos as its output is only 5V. The RJX FS0521 Servos' minimum operating voltage is 6V.

    After further thought, since the BEC and ESC are connected to the 12s batteries in parallel at one connection point, if the ESC fails power is still directed to the BEC, which then powers my servos and Rx. Therefore, in the event of ESC failure in the air I will still have control of the servos and be able to land, correct?

    I attached the BEC instruction sheet. The wiring diagram is on the lower left.

    The reason I did not contemplate a 2s Rx battery straight to the iKON FBL is the weight. However, this might be the simplest, best way to go and just can the BEC idea....

    View attachment WR Hercules BEC MANUAL.pdf
     


  2. murankar

    murankar Moderator Staff Member Armed Forces

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    The scorpion backup is a 2s Lipo. I am not sure what the output voltage is on it.

    The job of the backup is to provide power once voltage drops below 5v. When that happens the backup kicks in until voltage reaches 5+ volts.

    I think I may have herd that it only does 5 volts. My memory is foggy on it since I don't use one.

    Sent from my LG-E980 using Forum Runner
     
  3. Island Breeze

    Island Breeze Senior Rc-Help Member

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    That is correct on the ESC and BEC in parrellel. Exactly how i ran my electronics on my Gobbie when i had it and thats the way it is now on my LOGO. Keep in mind your tail servo voltage, you may or may not need a stepdown voltage regulator.
     
  4. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    The scorpion has a max output of 5V. My cyclic and tail servos all run 6V - 8.4V. The Hercules Super BEC has switches on it to set the voltage at 5.2V, 6.0V, 7.4V, and 8.2V. I want a simple system that is light, and offers servo control if the ESC fails. I could go so far as to say I need a backup battery for the battery and on and on but then the bird would be so heavy it wouldn't get off the ground.

    Correct me if I'm wrong, but my BEC will handle up to 14s input, which means that I can hook it up at one connection point with the ESC (parallel as mentioned in my prior post). Most diagrams I see have the BEC connected to only one of the 6s batteries in a 12s system. If this is the case then I don't need the Scorpion back up.

    Question now is how do I get the huge 8 gauge ESC wire and the 16 gauge BEC wire into one EC3/EC5 connector?
     
  5. Island Breeze

    Island Breeze Senior Rc-Help Member

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    Yes one connection point at connector where ESC meets batt conn. just leave enough bare wire before connector for you to solder the BEC and heatshrink it after.
     
  6. Island Breeze

    Island Breeze Senior Rc-Help Member

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    My quick auto cad drawing...lol image.jpg I hope someone else has a better drawing or concept

    image.jpg
     
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  7. pvolcko

    pvolcko Well-Known Member

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    Okay, lets break this down a bit:

    1) 14s power to your BEC: While the BEC may well be able to handler 14S input voltage, it is generally better to feed BECs 6s (for 12s series systems) or 7s (for 14s systems). The reason is that at full 12s/14s input voltage at least some BECs have limited ability to deliver high current on the output. The less voltage step down they have to do between input and output, the more current delivery capacity they have. So feeding them 6s/7s is preferred. Always connect it to the first battery in the series (the one going to the negative/black wire on the ESC). For this reason, many people choose to wire things up a little differently than Anthony depicted:

    wiring-1.jpg

    It takes an extra connector and a little extra 10ga wire, but it keeps your options open. I also put a small EC2 connector inline on the pair of wires going to the BEC from the main battery connector, so I can plug a small 2s or 3s pack (depends on minimum input voltage of the BEC) into it on the bench, preventing powerup of the ESC and motor as a safety measure. Excuse the lame drawing. Used photoshop since I hadn't yet installed a vector drawing program on this new laptop.

    2) Scorpion backup guard: This device will feed power to your Rx/FBL/Servos in the event that the BEC fails (or if main battery power were to fail). If the BEC is built into the ESC, then it could be said to be a safety against the ESC failing, but in reality it is a backup to the power source for the Rx/FBL, the BEC and/or Rx battery pack.

    3) 6vdc minimum operating voltage: They will work with less voltage, but the performance will be greatly reduced. In an emergency situation where you've experienced a main power loss and the SBG is powering the electronics, this isn't a concern. You *will* be landing promptly, one way or another. :) In the rare case where the BEC fails but you still have ESC and main batteries, the 5V and 10A max power to the flight systems will result in control be very draggy and lacking authority. You will notice it and you will bring it in for a landing to see what the problem is.

    wiring-1.jpg
     
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  8. Island Breeze

    Island Breeze Senior Rc-Help Member

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    Correct Paul But I believe his BEC model can handle an input of 45v and a output voltage selection of 4.4v to 8.4 volts.

    Okay bye.. Heading to airport again.
     
    Last edited: Feb 19, 2014
  9. pvolcko

    pvolcko Well-Known Member

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    I don't doubt it. :) But just because it can handle 45V intput doesn't mean it has the same current output rating at that input voltage as it does at 22.2v input. It may. Wester Robotics put out great units and so they may well have high current output regardless of input voltage. I don't know if I've even seen specs on them one way or another on this score. But I do know on others, such as a CC BEC Pro, the output current is severely limited at 12s input compared to 6s input. So, why not wire it to use 6/7s input instead of the full 12/14s? At the very least you're making the BEC's job easier at high current demand and perhaps lowering it's operating temperature. Maybe it is unnecessary, but it doesn't hurt. :)
     
  10. Island Breeze

    Island Breeze Senior Rc-Help Member

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    True! I do like your way though for maintenance and all. Well gonna go on my Mini Vaca again. shooooots
     
  11. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    Thanks for your diagrams, I think I get it now. I have some 10 ga wire to make the series adapter between the ESC and batteries. So, I could actually do a Y adapter on the BEC side. Which connectors are you using. I had a hard enough time getting a 10g a wire to fit in an EC3. How do I get an 8ga with a 16g a in one side of the connector without use something like the Dean's connectors, which I would rather not use since all my birds have EC3.
     
  12. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    The Hercules Super BEC G2 says to plug the servos into the BEC and then the BEC to the Rx/FBL. There are 4 ports for the Rx side and 4 ports for the servo side. If I am looking at this correctly, the Scorpion could only supply backup power if it was plugged into the servo side of the BEC, correct?

    If the Scorpion is plugged into the Rx/FBL would power be supplied to the Rx wires plugged into the BEC and then through the bus inside the BEC to the servo outputs on the BEC? I guess this would depend on how the BEC was manufactured. Whether the Sorpion would work during a failure would then depend on where the failure was.

    It seems I way to worried about this.....but with the winter we have had I have nothing else to do but sit around and think about failures during my flights!
     
  13. murankar

    murankar Moderator Staff Member Armed Forces

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    You can have a multitude of failures while flying. Bearings fail, battery cells drop, voltages drop or spike, links fail and gears can strip just to name a few. The one failure that most don't want is a bec or esc failure.

    My only suggestion is to setup A's many fail stops as possible and prepare the best you can for the rest. Lots of SIM time with random component failure turned on.

    Sent from my LG-E980 using Forum Runner
     
  14. pvolcko

    pvolcko Well-Known Member

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    On 550 size helis and up I use EC5's on all main battery connections. EC3's are too small and may fail (i.e. melt, result in short circuits and fire) under the current load seen on these larger helis. BEC to battery I usually use an EC2 because there is usually a max of 10-20A flowing through it worst case, normally far less.


    I haven't used one of these BECs before. It must have a power buss in it for the servos and Rx/FBL. Hopefully someone else knows how to wire in the guard on this setup. I'll have to do a bit of research. As you suggest, hopefully you can plug it into a free port on the FBL/Rx and the power will flow down to the BEC's buss and distribute properly to the servos. Most likely the case.
     
  15. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    Just reviewing your diagram pvolcko and am wondering which plug on the BEC/ESC side would be connected first? Would you arm the BEC first that way you have power to the controls and the ESC would read the throttle down position and/or the throttle cut switch on as to not start spooing when power is connected? However, isn't there a failsafe in the ESC wherein the ESC will not arm until it reads a low throttle position?
     
  16. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    Also, for all intents and purposes the BEC is just a voltage regulator, correct? Can I use the BEC in a stand alone Rx circuit or does a BEC have to be wired into the 12s/ESC circuit? Granted, I will have to put another battery onboard to power the circuit, which will result in an additional 230+ grams of weight......the whole reason for a BEC to begin with.

    In other words two circuits:
    1) Power the ESC with the 12s batteries.
    2) Power the BEC/Rx circuit with a 4s LiPo battery (According to Western Robotics I need a 4s input for the Hercules Super BEC G2 to run the servos at 7.4V)
     
  17. pvolcko

    pvolcko Well-Known Member

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    I leave the BEC plug connected all the time so in normal use I only ever plug in the main battery, the whole thing lights up and goes through initialization. Only time I use it is on the bench when I only want to power up the electronics sans-ESC and motor.

    The ESC and BEC/Rx/FBL/Servo side can not be totally independent. The throttle line connects the two. As such, at a minimum, you must connect the negative input of the ESC (from main batter) with the negative input of the BEC (from Rx pack). This will make both operate at a common "ground". Without this connection, the throttle line from the Rx/FBL to the ESC would end up having a different reference voltage compared to the power side of the ESC and would end up with a small current flowing through the line which can potentially damage either the ESC or the FBL/Rx.

    Later on I'll do up another diagram to show this kind of wiring, unless someone beats me to it. :)
     
  18. pvolcko

    pvolcko Well-Known Member

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    As promised:

    wiring-2.jpg

    Given that your selected BEC requires 4s power, I would not opt to power it via a separate Rx pack, I'd just run it off the 6/7s main battery pack (Option 1 in above diagram). However, if you're planning to run it at 7.4v output, that means you're running HV so you could also go with Option 2 and use a 2s pack directly into the FBL, skip the BEC all together. If you keep it charged every 3 flights or so (depending on the capacity of the pack) you will never notice any power drop off or performance hit on the servos.

    Also, expanding on Note 1 in the diagram, if you choose to not use a separate Rx pack, you can either leave that connection in or take it out. Leaving it in gives you the option to fly with an Rx pack later if you wish.

    wiring-2.jpg
     
    Last edited: Feb 21, 2014
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  19. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    :notworthy:Thank you so much, Paul!:notworthy: The ground in Note 1. This is necessary for the reasons you stated in an earlier post on this thread, correct? Sort of like a car wherein you have the ground strap to the chasis????
     
  20. HeliDinoRC

    HeliDinoRC Senior Rc-Help Member

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    What about the throttle lead from the ESC? is the postive on this lead a power feed from the ESC/Throttle to the FBL or a power feed from the FBL to the ESC/Throttle?

    The EDGE 120HV does not have an internal BEC. The Castle instructions for the Edge 120 HV ESC say not to disconnect the red power wire on the throttle lead when an external BEC is used. The Western Robotics instructions tell me to disconnect the red power wire on the throttle lead???? Who's right???

    The throttle is contained within the ESC. However, it needs to be powered and needs a signal from the FBL/Rx. Hence the throttle lead from the ESC that plugs in to the Rx. Given Castle's instructions, apparently the throttle is not powered internally by the ESC and needs power from the BEC or 2s Rx battery powering the RBL/Rx. Logic tells me that the power lead to the throttle needs to be connected if the ESC does not have an internal BEC to power the throttle. I'm confused as to why Western Robotics says to disconnect the red wire of the throttle lead from the ESC. Maybe they are assuming that an ESC with an internal BEC is being utilized and it needs to be shut down when the external WR BEC is used?????

    - - - Updated - - -

    A call to Western Robotics is necessary.........
     

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