Peter Beeney

Reading leccyflyer’s OP account regarding the black wire corrosion certainly brings back a few memories. I got into model batteries fairly early on, during the single channel days I guess, probably as a result of my occasional tinkering with full-size cells anyway and also having some bits of kit to be able to check battery condition etc. This snowballed into a Fred Karno style ongoing battery management scheme for a number of fellow modellers right up until lithium replaced nickel. Along the way I did run into the dreaded black wire disaster a number of times and I have to say that I never particularly noticed that it was in anyway the result of any moisture related conditions; but that's not to say that it wasn't of course; and even in it’s very early stages of destruction I think it may have been a bit dangerous. When the Schulze Chamäleon 6-936 charger, the one with the big screen, appeared on the market I instantly bought one, it was a bit expensive at the time but it quickly proved to be a godsend as regards testing battery packs. There was always a charge/discharge curve trace-out on the screen and therefore any faults were instantly plain to see…and it also had a little trick up it’s sleeve that perhaps even Matthias Schulze, the chap that designed it I believe, was unaware of at the time - at least to start with anyway. A helicopter flying friend handed me a receiver pack, slightly bigger than AA size as I remember, and asked if I might check it out for him. He also said he’d bought it new not very long before, it was okay in the chopper but his charger didn't like it too much for some reason. His charger was okay with all other packs so I started to discharge it for a test and instantly the trace on the screen was different, it was decidedly ‘fuzzy’ because it’s edges were very slightly crinkly making it wider and slightly lighter in colour than normal. It was discharging ok however so the next thought was check the wire and after taking a good look at it I noticed that the neg pin in the plug was just a shade tarnished and dull looking but that was the only evidence I could find of any corrosion. However, straight away I renewed the whole wire which I'd done once or three times before on other packs and problem solved! As regards capacity etc. the pack was spot on. In another incident long ago, I’d previously obtained a multimeter which I still have, it lives in a very nice zip up case and it uses a PP3 battery for power. At one stage I thought I was being clever and I gave it a rechargeable to eat which worked fine until I happened to noticed an odd glitch, can't remember now exactly what it was, then that battery came out of it faster than light and low and behold there was the dull appearance on the negative press stud. As you can imagine then and there I made a vow to never again use a rechargeable PP3 in any other test instruments that I owned that used them…. I think one of the worst cases I ever saw was in a 40 powered size model that had been hanging up in a model shop for apparently quite a long time. Someone had installed an on-board glow driver, a single nickel cell back on the CoG and I suspect that to try and reduce any vote drop to the plug they’d used a piece of heavy gauge red wire taken from some twin and earth cable used in house wiring. An on/off switch and a recharging socket completed the set up. It had become a bit of a mess really, the top of the cell was completely corroded away and all the metal content of the whole caboodle had completely turned to black stains; I suspect this was not a one off either, I'm sure there must have been other such cases. I also found that once the rot got started in a wire disconnecting it from the battery made no difference at all, even when sealed in a plastic bag it just kept going apace until it was all just a dusty memory…… Re the tinned wire, Futaba tried using that idea at one time for the negative leg of the their battery connector wire, maybe they still do, but I saw definite evidence that it could still get attacked; I was going to do a trial with some silver wire but I never quite got around to trying it. Fortunately it's certainly didn't happen to all battery packs by long chalks and I've still got a pack of nicads which are now well over 40 years old and still in the best of health…… Happy days! PB

Yes indeed GG, my thoughts exactly; and particularly in view of the fact I can't think of a way of permanently preventing the voltage regulator working even with the battery connected. With great respect all round of course but I think I would be having a little chat with Overlander pronto to see what their thoughts were and then I think I would be very surprised if in turn they didn't have to consult the manufacturer. I suspect you meant to say ‘on plugging in a fresh battery.........nothing’. Very odd might just prove to be something of an understatement eventually……. PB

Just to fill in a little more time here with a bit of the idle rambling stuff and getting back to the BEC I'd say it’s actually quite difficult to permanently zap a voltage regulator, at least in the normal run of events anyway. They normally have a bit of built-in protection circuitry, such as current limiting and a thermal cut-off point specifically to prevent self destruction. I did a spot of tinkering with a couple of 6V 1A regulators a very long time ago now, I hooked up a 12V SLA to the input, attached a suitable resistor on the output to well overload it and couple of meters in circuit to check out what was going on. It fired up okay, got finger blistering hot… although I didn't try it… the cut-off temperature is 150°C…, it then shutdown with very little output, a few erratic milliamps that just jiggled about, then cooled down in a fairly short time, it was out in the open air after all, reset itself and started to heat up again. It carried on like this for a while so I just left it talking to itself for at least 24 hours or more. When I disconnected the resistor there was the normal steady 6V as usual so I just left it like that for a couple of days and then did it all over again using the other one with exactly the same result. It certainly did not appear to do any lasting damage to them whatsoever. Of course if you were to shove reversed polarity at it or seriously apply over volts, (the ‘never exceed limit’ is 35, don’t even go anywhere near there) or hit it very hard with a small club hammer you probably might render it rather mortuus elektus but that's only pure vandalism. That doesn't really count. This seems to explain a couple of things that I’ve pondered on in the distant past. Firstly the sheer and utter tenacity of some of the solid-state electronics to insist on keeping going in sometimes the most hazardous and hostile of circumstances, but it’s also a very plausible explanation too perhaps of another rather mysterious calamity that used to happen on the very odd occasion. When electric power first started to become popular someone would be zipping about quite happily and then suddenly have an unexplained crash due to apparent loss of control but then when the pilot and others reached the splinters they usually found the radio to be working okay; resulting in some scratching of heads....and even more splinters perhaps… However, when I explained what I thought might be happening that would be accepted plus some ideas about adding a bit of ventilation to help keep things cool also went down as a good idea. Fortunately a good cooling through draught is now the norm… Although 150° does seem to be quite hot it occurred to me that when you place a piece of kit, namely the battery and the ESC, in a polystyrene foam box with little or no ventilation then they may well get hotter faster than the heat can escape resulting in the ESC particularly getting very hot indeed; and with the BEC right in the middle of it, (or probably towards the front end I guess) it's not long before the temperature gets that high. Cooling down would be slower too, perhaps I should have noted the time and temperature fall before it restarted… Hope this helps. I have to admit I wouldn't know where to start on an ESC to prevent the BEC working even with the flight pack connected, let alone when it's not… One for the manufacturer I reckon. Just an opinion, kick it to death as much as you like. Good luck. PB

Hi Toto, Just so that I can reiterate a little here as well, you now have four ESCs which you cannot use because there is no 5 volt supply on the throttle lead. If this statement is correct then I think in the first instance I would have to at least consider these items to be well in front to be the potential problem; and more specifically the BEC because this is what supplies the 5 volts. This is what I might do to establish the exact conditions in these circumstances: Firstly I’d find a flight pack with some charge in it together with an ESC that I know to be good to go. Then any receiver that's just handy. I’d plug the throttle lead into the receiver, any channel, and a red flashing LED will appear. That's my benchmark indicating that I've got power okay. I’d then disconnect that lot and just swap it for my faulty ESC. Now I will either have a flashing LED or not. In the case of it flashing then I’d contemplate that I've got a problem that's currently undiagnosed; and unexpected to boot.. In the case of it not flashing then I would definitely know that there is every chance that the regulator/BEC was certainly blown. Now I’d disconnect that lot and reconnect the original back again to prove everything is still good. Lastly I’d find the other three miscreants and try those in exactly the same way. I certainly don’t think this is in any way “manufacturer bashing” or indeed anything that you are doing wrong; there’s not really much in the way of a lot of other kit that you can point the finger at either. But I think you would have to agree that from the general tone of some of the recent posts this is certainly a very very unusual set of circumstances……. You may well be surprised how little time this actually takes to do if you decide to try it and I’d like to wish you all the very best of good luck with whatever you choose to do, I'm sure you will soon be able to tell us exactly what is going on. Just my take on this problem. PB

Yes indeed Dale, may I say that's a perfect answer to what on the face of it is apparently an impossible question. I have to admit I was also beginning to think along the same lines but I couldn't think of any situation where I would want to pull the throttle lead out of the rx. Also could I have done this at least four times without somebody else noticing either?? It seems to me that just this simple point is seriously questionable too. I think if Toto does prove beyond any shadow of doubt that there is no 5 volt supply from the ESC and the others are exactly the same then Overlander should at least be advised of this problem. Or, of course, that being the case, they may already have an inkling anyway. Really like the ‘then you are the only person in the history of RC flying that this has happened to.’ bit; Toto’s claim to fame perhaps; however, should it transpire that if this particular ESC version is prone to failure for whatever reason then maybe someone in a dark corner of a model flying field faraway is doing their level best to play catch up... I feel we are close to getting an answer….. or more likely some further interesting questions….. hopefully….. PB

Philip, My apologies, I guess I was a bit too vague there. This is only my opinion of course but I would consider that if the regulator (BEC) is blown then there is no power to some of the components and therefore the ESC is unable to function at all. Neither can the radio because there is no power supply there as well. I very much suspect it would've failed open circuit, if it failed short-circuit it would then most likely destroy itself fairly quickly and then become open circuit anyway, leaving the pos and neg wires in place between the rx and ESC provides the complete circuit for the battery connected to the rx to then provide the 5 volts for the necessary components on the ESA. Admittedly the supply is now a bit back to front but that doesn't make any difference at all. I think I can say with some certainty though that disconnecting the red wire will indeed definitely prevent this cobbled up arrangement from working at all. Sincerely hope this makes better sense…. PB

Hi Philip, With total respect but it may be worth sounding a tiny note of caution here. The BEC is a regulator and if that has rather popped its clogs then I’d consider that the whole ESC is in something of a major malfunction too, it’s going to be a bit inert to say the very least. However, if the red wire is left in place and still connected then plugging a battery in will provide the necessary 5 volts to power the radio and ESC for more sweet and harmonious loops and rolls…. Having said that I think my strong preference though would certainly be to return it to the supplier and get his angle on it…and hopefully some sort of recompense as well… Although this arrangement might work for a long time and indeed never give any problems I feel that because this is not how it’s designed to work I would not have sufficient faith in this. Not something I’ll be doing anytime soon, at least in the normal run of events anyway. Cheers PB

Toto, If you would rather not check this with the ESC plugged into the receiver have you got some other means of checking the voltage output on the throttle lead from the ESC? Voltmeter perhaps if you have one. From your description of the fault it does seem difficult to consider it as anything else other than that the regulator has gone open circuit for whatever reason. I'd of thought that for this to happen just once is bordering on virtually unprecedented, the frequency at which it appears to be happening to you is pretty well right off the clock… If it does so happen that the regulator has gone open circuit then it may be well worth considering that the others have also done the same….. which is quite remarkable but I have to say very difficult to see that it's maybe anything that you are doing incorrectly either. I think you are getting close to cracking this! PB

Toto, Thanks for your prompt answer and I have to say straight away that I can't give you an absolutely definitive answer without having a quick look at the bits and pieces but if in fact your Domino motor does run when you connect the receiver battery I would have to say this points inexorably to the voltage regulator a.k.a. the BEC. This regulator supplies a steady five volts to some components on the ESC which would seriously object to being connected to the flight pack voltage. It also provides the supply to the receiver so if this suddenly ceases to function for some reason when you connect the 5V battery that simply replaces the regulator supply and back feeds the said components. For the moment establish beyond doubt the motor run, or not run, condition and we'll take it on from there….. I'm sure you can't do any harm here but as usual please consider the prop turning without warning and also I'd have to say I'd find it very difficult to find any other sort of explanation external to the ESC that might cause this situation. Take it easy. PB

Hi Toto, Very briefly, I've just been reading some of the later posts of this thread, I've by no means read it all I'm afraid, but with regard to the failing Overlander ESCs can I respectfully ask if they are all the same version, i.e. same current supply and price or have you used a variety of types and sizes? Also in your post at 16:45 on Saturday where you mention the ESC failing in the Domino and then when you plugged in a NICD???? battery everything worked, did this also include the throttle/motor as well do you remember? An equally brief answer will be fine. Many thanks. PB

Indeed, I couldn't agree more Don. Disconnect the push rod from the server arm and just anchor with a 5A electrical ‘chocbloc’ . If I were a learner at this stage I’m sure would be asking the instructor for some takeoff practice as well, flying basic square circuit, left or right as the site orientation dictates, overflying the strip and the next stage is a landing approach. I think that getting used to flying near the ground would really inspire my confidence, and indeed, I too have to abide by the KISS rule, Keep It Strictly Simple, anything else would be a bit too clever by half…. A very long term, from single channel days, flying colleague had a couple of maxims he always quoted to beginners, ‘If you think you are going to get upset crashing a model aeroplane, don't even start,’ and secondly ‘If you don't fly in a wind you will never do any flying’ and I must admit I don't think I've ever had any occasion to argue with that. Over the years I don't think there is anything else that quite comes close to sometimes turning normal rational human beings, usually the more senior type, into more or less quivering imbeciles than learning to fly a model aeroplane. One little bit of advice I tend to throw out right from the start is ‘Whatever happens. try to appreciate and enjoy all this scary stuff because you won't be able to experience this twice’ and of course the the same applies to the first solo flight, you only ever do it once. Blue skies PB

Another attempt at an answer to this conundrum and to be fair all round I’ve considered the original question. Reproduced below. But to be honest I think Paul's O/P is near enough to make no difference anyway so this is an answer to that as well. If indeed this is an answer, though, it may well be just rubbish.. Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off? And now imagine this sentence is a free hand sketch of a 747 standing on the conveyor belt!! I would agree with Martin, providing we keep absolutely to the spec. in the statement above then the plane cannot move forward. With regard to the timing would say a picosecond lead/lag time be sufficient and would this actually be obtainable in practice? In today's technical world I think it may well be yes to both… The plane is standing on the conveyor belt. We make a chalk mark on the side of the tyre on the bottom of the wheel and another one to match this on the the conveyor belt. Then a 3rd at the side of the conveyor belt on the ground to mark the position of the axle in the centre of the wheel in relation to the ground. At this stage the wheel is held firmly in contact with the conveyor belt by the weight of the plane bearing down vertically through the axle. The pilot opens the throttle, the thrust increases and the plane starts to move slowly forward due to the pressure of the axle moving at right angles to the vertical forcing the wheel to turn forwards against the friction of the belt. One picosecond later said belt starts to move backwards and from then on in keeping strictly with the spec. it's speed is inexorably linked exactly with the speed of the accelerating wheel. Normally the wheel would of course move forward on a stationary runway but now the wheel’s point of contact moving forward is meeting the belt’s point of contact moving backwards at exactly the same speed, the nett result causing the wheel to revolve around the axle but keeping it in a stationary position relative to the ground beneath the belt. If the circumference of the wheel is 15 feet after the first revolution we note the chalk mark on the belt is 15 feet behind the wheel but the chalk mark on the ground is still exactly in line with the axle…. and probably much more obvious, the plane itself has not gone anywhere either! The second revolution is the same as the first except that the speed of the whole process is accelerating due to the forward pressure on the wheel’s axle and will continue to do so. Therefore, again like Martin, I think this is going to eventually end in one almighty tangle. Also I think crucially not only does the speed of both items have to match but also the power output as well, it seems to me that the two forces have to equalise. Maybe the power supplied to the belt would need to be in excess to that of the jet! So now is it possible that before the wheels start to come off the wagon natural inertia becomes great enough to keep the process at a steady speed at some point? I've no idea, maybe it’s the next silly question perhaps… I would consider that as long as the belt speed stays in exact sync. with the speed of the wheel then the axle and thus the plane is never ever going to move. If the pilot shuts the throttle, say to around half, maybe that would still be enough force to keep the wheel turning and then if the belt stayed in sync going backwards too you could sit and watch the wheels going round with the plane going nowhere. But it sure would cost a bob or three I reckon. PB

Hi Martin, Thanks for your post but I’m not quite sure exactly what I need to say here. I’d certainly be more than happy to address this specific point about the wattmeter and resistance etc. for as long as you wish but I wouldn’t be making any changes in my narrative. Also I don’t remember that I ever said that the wattmeter was superfluous, as I remember I said ‘I’m reluctant about the wattmeter, in my view this is just telling me how many volts and amps are being converted into heat due to the resistance of the power train….. I have no problems whatsoever with anyone using a wattmeter. If you wish I’m more than happy to describe exactly how I view the circuit and it’s resistance just from the most basic point of view. Then you can take it completely apart right down to the last nut, bolt and spring washer and explain precisely what I’ve got wrong. If that is not a satisfactory solution can you suggest an alternative? Just for interest in an idle moment I’ve just had a quick Google this morning and in about two seconds flat this was the very first hit. So I didn’t really bother looking for any more….. it’ll do just nicely for starters at least…. It’s a copy and paste as written, the upper case and bold text are the author’s own, not mine. When a current flows through a resistor, electrical energy is converted into HEAT energy. ... The rate at which the heat is dissipated is called POWER, given the letter P and measured in units of Watts (W). The amount of power dissipated can be worked out using any two of the quantities used in Ohms law calculations. And also for what it’s worth, here’s my take on someone’s ‘I squared R is not always V times A’ thingy from earlier in the thread somewhere. When W = watts, V = volts, I = amps, R = resistance. Let W = V x I = V x I From Ohm’s Law V = I x R Substituting, W = V x I = I x R x I Or, W = V x I = I squared R And Let W = V x I = V x I From Ohm’s Law I = V/ R Substituting, W = V x I = V x V/R Or, W = V x I = V squared over R Ironically I can still remember my very first post on the forum, as can many other folk I guess. It was indeed a long time ago, I didn’t even have a computer back then, I often visited the local library and communicated from there. Cutting edge CRT technology at the time, (for the library!), with a Windows OS of course… . which perhaps explains why I’ve used a Mac ever since! There was a debate going on even back then about electric motors together with AC and DC current etc and for whatever reason at the time I said that that the true expression for watts was volts x amps x power factor. There was a general consensus of agreement with this but as it was also thought that it didn't very much matter with our motors and as nobody wanted to go anywhere near this anyway we’d best forget all about it. Something with which I’ve totally agreed with ever since… So now I’m thinking it’s quite possible that my last post on the forum will also be related to watts as well. They say that what goes round comes round…. Regards PB

Sorry if I was giving that impression Martin, the problem I have is this; Mike is multiplying the 10 volts of back emf by the 20 amps of current flowing round the complete circuit to give the motor 200 watts of power and I seriously cannot understand this. For a start the back emf can never equal or exceed the battery voltage so the back emf can never complete it’s own circuit anyway; so therefore no current will ever flow. I believe that the 20 amps is established by the 11 - 10 = 1 volt applied to the motor’s resistance. The motor’s rotation is creating the back emf, not the other way round, so how can any power developed from the back emf be used to power the motor? May I ask if you agree with this so far; and if not exactly why it’s incorrect and therefore how we actually can develop watts from the back emf. Also I made a boo boo, or perhaps yesterday's deliberate mistake… I think the battery charging rate should be: 20 amps to 200Ah is 0.1C, to a 20Ah battery it’s 1C and to a model’s 2Ah pack it’s 10C. Many thanks. PB

Hi Mike, Thanks for the reply. I’m afraid I still have just as any problems with this. In your first motor example I’m assuming your wattmeter is connected in the circuit and you are quoting your values from this. So it would be reading 220W. If not I’m not at all sure where to go with this anyway. I consider the 10V of back emf as being effectively cancelled out by 10V of the battery supply which in turn is also being cancelled out, leaving the 1 volt to provide the 20 amps total circuit current which results in the 20 watts. I believe that the back emf cannot create it’s own current flow, it’s p.d. can never equal the incoming battery voltage, also the existing 20A current is flowing the ‘wrong way’ anyway so just how we can say this is is producing any watts I cannot grasp at all; at the moment of starting there is no back emf so how did how the motor get started without it and how does 200 watts go into powering the motor, where and how is the connection made and what is the exact technique used. Finally if the motor’s own back emf is actually supplying watts back to the motor then it would appear to be powering itself…. I think it’s gonna take me a whole month of Sundays and then a whole year more as well to get even just half a handle on this lot… And it still begs the question, where did the the watts from the rest of the circuit disappear to….. Regarding the battery charger, if we saw 10 volts and 200 watts on a meter between the charger and battery we would be charging the pack at 20 amps. That’s ok if it’s a 200Ah lump, it’s a rate of 1C, but if it’s a model pack I think it’s probably a mite ambitious. To use this battery charging analogy I think it really makes my point - just like the motor powering itself, it would appear to be charging itself… To enable a current to flow into the battery the charger voltage has to be raised above the battery voltage and at least up to the fully charged voltage of the battery. The charging voltage is simply the difference between that of the discharged pack, say 9V, and that of the max output voltage of the charger, say 12.6V. The charger output will be constant voltage with current limiting until the charge is nearly completed at 12.6 volts because charging needs to be a relatively slow process. The charging current flowing backwards though the battery and it’s voltage is just reversing the chemical action that took place to provide the electricity when the pack was being discharged. Because of the current limiting a wattmeter in the charging circuit will always read the rising battery voltage, let’s say it’s at 11.1V at some point, the current is flowing at a constant 2A and so then the meter would read 22.2 watts. I certainly agree that when the motor isn’t turning there is no back emf but a number of possible reasons. Maybe the battery is just disconnected. Or still connected with the throttle fully closed. But if the throttle is fully open, the prop shaft prevented from turning and the full battery voltage is reaching the motor then this may soon become apparent by the sound of the blues and twos coming down the road on the hurry up to put the resultant fire out…. Definitely no output power but certainly maximum input power now though. Now I’m off to make a toasted cheese and onion sandwich. There’s nothing quite like toast burnt over some hot embers…… Sorry about the delay, for some reason my password seems to have been changed. Regards. PB