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ESC + BEC Reliability

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  • ESC + BEC Reliability

    A poster questioned whether the long battery leads in some birds possibly create reliability issues for ESCs.

    I know cross posting is discouraged, but this is a more suitable place for the response.

    -GG

    Please visit the below.




  • #2
    Link above is invalid

    There has been comments about long leads on ESC.

    Could be more specific on which leads you're talking about, whether the motor leads or the battery leads. I've had long battery leads on many aircraft with no issues. All the way up to 7s. Long battery leads create some resistance depending on the thickness of the wire. Not really an issue unless you're looking for extreme acceleration. It would actually be easier on the other components. Battery ESC motor.

    Long leads from the motor maybe a different situation. Some EMF may be generated.

    Some users of expensive ESC's have reported ESC failure due to other issues like the capacitors on the HV esc going bad causing the FET SEMICONDUCTOR circuitry to go bad. Supposedly the capacitors on especially the high voltage systems are there to prevent the EMF. I suspect the capacitors are connected to the input voltage or battery voltage. Because it's usually two capacitors. Sometimes a bunch in parallel.

    I did have a ESC 7s or 30 volt go bad on me In flight. That defective ESC estimated 14 years old. I simply double the amperage of the new ESC.. I had four of the same ESC and only that one went bad. SO FAR IN ABOUT 15 YEARS. I will keep my fingers crossed.

    Comment


    • #3
      Send Kallend a PM for all the details.

      He posted at…

      https://www.hobbysquawk.com/forum/rc...867#post282867

      The caps on the battery/power wires are to mitigate the inductive effects of long power wires…keeps from blowing the ESCs up.

      The caps are not to mitigate RF noise.

      -GG



      Comment


      • #4
        Hi Alan. I found this article in Model Airplane News and referenced Astro Bob
        It likely answers your question . This is just an excert because I couldnt find the link to share.
        Battery to ESC short
        ESC to Motor can be long
        Cheers
        Bob
        Wiring Basics
        This is a big motor requiring a large speed control and unfortunately, this one isn’t up to the task. Adding to the problems is the small gauge wire and adapter using uninsulated bullets. This system was caught and changed before there could be a problem.

        A question I often hear is, “Is it better to lengthen the wires from the battery to the speed control or to lengthen the wires from the speed control to the motor?” Online forums are full of ideas, opinions, conjecture, and debate over this question. Let me give the simple answer first; it is better to lengthen the wires from the speed control to the motor and keep the battery wires as short as possible. That’s it, plain and simple.

        The debate arises over resistance and inductance. It’s argued that using a larger gauge wire reduces the resistance, making Recipe for a Cooked longer battery wires acceptable. While it does reduce resistance, it doesn’t take into account the increased inductance it causes. Proponents of lengthening the battery wires say that can be overcome by adding additional capacitors to the front of the speed control. This is a patch, not a fix. The speed control comes with capacitors installed as determined by the manufacturer for its intended application. Without specific knowledge on current and how good the flyback diodes are, along with the switching speed of the FETs, voltage rating of the FETs, and types of FETs, you’re grasping at straws. If you do know those things, you’ll still need to do a lot of math to figure out the appropriate caps to add.

        Recipe for a Cooked Speed Control
        • Take one undersized speed control
        • Add cold solder joints
        • Use extra long wires from the battery to the speed control
        • Pack it in a foam plane with no cooling air
        • Fly partial throttle settings extensively
        • Push the BEC to its max limits and beyond
        • Fly consecutive flights without a break

        Here are quotes from AstroFlight’s Bob Boucher on the topic of which wire to lengthen:
        • Wire resistance may rob you of a bit of power, but it will not destroy your speed control or motor.
        • Wire inductance will not damage your motor nor will you be able to detect any effect even with 100 feet of wire.
        • Wire inductance will kill the mosfets in your controller and may even blow the caps. Ed. Note: Bob is comparing inductance in the motor to speed control wire with inductance in the speed control to battery wire.
        • You must keep battery wires as short as practical. Short means one foot or less, brushed or brushless makes no difference.

        Bob is better known as “AstroBob,” former owner of AstroFlight and holder of a patent on electric flight. When AstroBob talks, I listen. Always lengthen the wires from the motor to the speed control if needed. The best possible solution is to keep all wires as short as possible, but we know that’s not always easy when you’re doing that special scale project.

        NEATNESS COUNTS
        All of these unsecured wires flopping around right over the receiver antenna will cause trouble. There is also 18 inches of wire from the battery to the speed control, and that’s WAY too much!

        Remember what your mother told you, “neatness is important.” A jumble of wires just stuffed into a fuselage can cause many problems, especially if they are unsecured and flopping around on top of your receiver antenna. We have become overly secure with our robust 2.4 systems, but wires moving around in close proximity or touching the antennas can and will cause reception problems. If you have so much wire that you need to bundle them or tie them up, take the time to trim them to the proper size. This makes the plane safer, but also shortens wires and decreases resistance. This counts whether it’s for your motor/speed control or servos.
        Mismatched connectors are ALWAYS a bad idea.

        Connectors & Adapters
        Note the securely attached speed control for this big power system and how the connections are well insulated and secured. Short wire runs and a protective grommet in the firewall, where the wires pass through, ensures no shorts over time.
        An improper extension made by jamming a bullet into the EC5 connectors. Great connectors ruined by a bad idea.
        A homemade parallel battery connector in a plane; wire nuts belong at home, not in your plane.

        There is no standardization between connector types, so most of us end up using an adapter at one time or another. Be sure to wire and solder them carefully. Double check the adapter before using it. The goal in electrics is to reduce the possibility for increased resistance in our circuits. This causes heat and wasted power. It’s best not to use an adapter, but if it’s necessary, be sure it’s properly sized and constructed. Wire nuts have their places in home wiring construction, but NEVER belong inside our aircraft.

        Check your manufacturer’s website to see the limits of their connectors. If you’re pushing the limits of your 4mm bullet connector, then go to a 6mm size. The same applies when you’re using EC3s or whatever brand. You want the most surface contact and least amount of resistance you can get for maximum efficiency from your system.

        Tips for a Happy Speed Control
        • • Buy a quality speed control
        • • Buy one large enough to handle the load
        • • Don’t exceed the BEC limits
        • • Provide cooling; all that you can get
        • • Keep wires as short as possible
        • • Use appropriate connectors

        NEVER mismatch connectors. I’ve seen Dean’s Ultras jammed into female bullet types and that is a recipe for disaster. I’ve also seen spade plugs shoved into the grooves between the contacts on a male bullet connector. Likewise, alligator clips have no place in an electric airplane. They may seem like a universal fix, but it’s actually a universal mistake. All of these things can be inefficient, but more importantly—they are all dangerous and create a fire hazard.

        MOUNT IT SECURELY

        It’s not always easy to find the right place to securely mount the speed control, but it’s absolutely necessary. Some larger controllers come with mounting brackets so they can be screwed to the front of a firewall, etc. Most smaller controllers depend on you to figure it out. Velcro is the usual method of choice and works well. Be sure it is secure though. If in doubt, use industrial strength versions or rigid lock tabs. Whatever you do, don’t allow it to flop around inside your plane held only by the wires.

        BOTTOM LINE

        No one wants to cook their speed controllers! As with everything else involved in our hobby, it’s the small details that matter the most. Avoid these common mistakes and you’ll maximize your airplane’s efficiency and greatly lengthen its lifespan. –BY GREG GIMLICK

        Comment


        • #5
          I agree with most of what was said.

          I have bought inexpensive ESC's and had good luck with them with the exception of one which did last a long time in a smaller aircraft but eventually failed in a larger aircraft. I believe that's only because it was underrated or just something went bad with it. A 90 size electric on a 100a ESC was not enough. It did have a CC ESC previously but it was only a six cell. I have a bunch of 7s batteries so I needed a 30 volt esc. Now I'm using a 200 amp esc. So far so good. Battery leads are not short.


          I always use external becs usually because they don't have Bec in ESC or knowing that you cannot trust a lot of ESC internal bec. A lot of people have made that mistake causing loss of control and a crash.


          Under rated ESC can either blow the ESC or even the motor too. Don't do it.


          The higher the voltage and the bigger the motor the higher the forces. That is why a lot of these expensive ESC call for added capacitors and short battery leads. The battery is actually taking power in as well as giving it out. Basically going back and forth.

          It is often not practical to have long motor leads to ESC. It's far more important to get cooling to the ESC. I've never used long leads to the motor.

          Comment


          • #6
            When you cannot get adequate cooling to the ESC, you must go big on the ESC. It will run cooler than that standard size. I have one aircraft that does not have the option of having the ESC in a well ventilated area. In fact my battery sit right on top of it. Aircraft came with a smaller ESC but I changed it to a larger one which runs cool and efficiently. I always go for the bigger size whenever I can for the aircraft that I or somebody has build. I have a bunch of Castle creations but I've changed out and number of them for a higher voltage using either hobby wing or a cheaper brand 30 volt ESC. Been working very well for the last 15 years or so. I never paid attention to battery lead length. Only lost one esc to unknown reason other than maybe a little underrated but it did work for years before it failed. I doubled the amp rating. So far so good.

            Comment


            • #7
              Update 2023-6

              I have used 6s batteries for a long time with long battery leads and have gotten away with it for a while. My ESC was rated for 30 volts or 7s max 100 amp ESC.
              Then I got a hold of 6 x 7s batteries and I started to use them on that same aircraft.
              The end result was over a period of time I went through two ESC's. Even when I switched up to 200 amp which the previous one was 100 amp which lasted a long time on 6s until I switch to the 7s.

              Now
              I've heated the warnings and have taken precautions and redesigning the layout where is the ESC is no longer in the front Cowling with the motor but in the fuselage in front of the battery where I'm using the wires that came with the ESC with no extension. I've also added a 3300uf capacitor 35 volt as close to the ESC I could get it.
              Not that I need to use it much but I've also redesigned a Y connector if not using 7s batteries but using two battery packs to get to 7s which I don't do really anymore. It no longer has wires but rather there's connectors solder together with only a half inch wire making one of the connections.

              We'll see how the new setup goes, only Time Will tell. But the facts are it was when I made the change to the 7s batteries that the problems came about. Not before. I was operating the ESC at his maximum voltage of 7s which is close to a 30 volt Max voltage of the esc's.

              My oldest ESC which is also a 30 volt ESC 100 amp that I still have I have shortened the leads on that one and added capacitor also and it is still going strong although does not get the amount of use as the main aircraft I've been using on the 7s but it too also uses the 7s batteries and has not failed yet even with the long leads and the 7s batteries previously. Didn't want to wait to see if that one would go too because another one just like it did on the bigger aircraft.


              ​​​​​​FYI
              I ordered a skywing ESC and it was defective from the beginning. I dissected it and discovered that it wasn't what it said it was. Capacitors were only 25 volts. The dealer sent me another one and that one lasted one flight until the thing started to malfunction. Erratic throttle control and so on. Got my money back. I then ordered a Red brick ESC and so far that one's going fine. After 14 flights. Keeping my fingers crossed.

              Comment


              • #8
                What kills the ESC with long battery leads is ripple over the wires. Capacitors absorb that ripple and usually allow you to use longer wires.

                Alan, you have some interesting info. What 7S ESC are you using? Do you have pictures of the installation, wiring, connectors, etc? I see you mention Skywing, I never heard of them. $24 for a 200A ESC? Not sure I'd trust them. I see on some they even misspell Skywing, Swywing!

                Comment

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