Steve Colman Posted June 8, 2022 Share Posted June 8, 2022 As a short break from a balsa glider build I'm finally putting together a Mpx Twinstar that I've had for 5 years. I know this has been discussed many times but I'd like thoughts on best practice between lengthening the wires between Motor to ESC v Battery to ESC. This will dictate whether I mount the ESC's in the fuselage or on the wing directly behind the motor and need to make a decision before I go any further with the model. Cheers. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted June 8, 2022 Share Posted June 8, 2022 The best practise is to lengthen the motor wires, but having said that the ESCs on my Twinstar brushless conversion are in the wing, as are the ESCs on my Catalina. Quote Link to comment Share on other sites More sharing options...
Steve Colman Posted June 8, 2022 Author Share Posted June 8, 2022 Thanks Frank. I'll follow your example as there are fewer wires to lengthen and the ESC's will get better cooling. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted June 8, 2022 Share Posted June 8, 2022 Hi, The best practice is to follow manufacturers recommendations as some say you should not extent battery leads, some say extend with capacitors and others say its not an issue. IMO there seems to be less of an issue with extending motor leads. Of course finding the relevant information might be harder form some suppliers hence why I use 4Max for non standard applications. Either email or best to phone George explain your application and purchase the necessary bits. If you do have an issue you can always give him a call and discuss. You pays your money and takes your choice and if you have the time and expertise you can get into the nitty gritty programming, but TBH I would rather be flying ? PS I have 5 twins all with long battery to ESC leads and they all work just fine as there is plenty of cooling in the cowls. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 8, 2022 Share Posted June 8, 2022 There has been much discussion about this. The problem as best I have been able to determine is a matter of almost random failure due to voltage spikes. The capacitors ahead of the input to the ESC are there to smooth out any voltage spikes which occur every time the ESC switched the amps from one pair of motor wires to the other. The spikes are small but smoothing them requires the capacitor to absorb energy and by doing so generates heat. Heat will eventually cause the capacitor to fail. Then the voltage spikes get through to the MOSFETs which will soon fail. Obviously the size and frequency of the voltage spikes and the amps involved determines how much power the capacitor(s) have to absorb. You can't do much about the frequency and the amps as that is due to flying but adding to the battery ESC wire length will increase the size of each voltage spike. So it comes down to a 'reliability' issue. One assumes by using the provided tails the chances of capacitor failure over time are suitably small but increasing the battery to ESC wire length will shorten the capacitors life by some factor but by how much is almost impossible to ascertain as there are many variables at play. It is of course quite possible that even a shortened capacitor life will still be longer than the life of the model. ? 1 Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted June 9, 2022 Share Posted June 9, 2022 Hi Simon, I have to disagree and hopefully if I explain you may see where I am coming from! I don’t think they are random failures because: · Manufacturers recognize there is an issue because they give advice as in do/don’t/fit caps etc. · Chatting with George he explained that it was an issue and that the products were redesigned to eliminate the problem. However as we know other manufactures either advise caps or don’t recommend doing it · Some manufacturers will use the cheapest, low spec components available to sell a product just fit for purpose. If its stressed by poor cooling, long leads etc then it is far more likely to fail. Yes the input caps are there, but IMO the fact that the battery is close and has a low internal resistance reduces the voltage spikes. Again if caps are used with lower voltage rating then its more likely they will fail and then stress the FET to the point of failure (especially if they are of a low voltage rating). If you use longer battery to ESC leads it puts greater stress on the capacitors from a peak voltage point of view as the battery is not absorbing some of that energy. I don’t think the amps are directly the problem, but more to do with the frequency of the voltage spikes, it’s the magnitude and rate of rise that damages the caps/FET’s A reliability issue? Not really if people don’t follow manufacturers recommendations, then they will stress the ESC to a point of failure – no surprise really. TBH I would have thought the failure would be quite quick as in seconds to minutes rather than hours or days, but I could be corrected. Having now written this I don’t think we are to two far apart, just the root cause of the issue. The solution is a redesign as George mentioned although I suspect that and a combination of higher rated capacitors (voltage/capacity) resolve the problem. These are my views and if you want to purchase a ESC rated for long battery/ESC leads and chat about the technicalities then George at 4-max has been very helpful in the past. Hope that helps in some way ? Quote Link to comment Share on other sites More sharing options...
John Lee Posted June 9, 2022 Share Posted June 9, 2022 This is all good background knowledge and very relevant in some installations. However in specific answer to the OP's question - don't worry about it Simon and put the ESC's in the wing as you intend. In the TwinStar the runs are so comparatively short & the components lightly stressed either way is not an issue. Like Frank the ESC's in mine are in the wing and have been operating without any fuss for about 7 years. Quote Link to comment Share on other sites More sharing options...
Steve Colman Posted June 9, 2022 Author Share Posted June 9, 2022 Lots of interesting reading; many thanks to all who contributed. Oddly enough I've now come to the conclusion that the best solution for me is to mount the ESC's in the fuselage. I only need to solder on some extensions from the ESC to the motor and no other mods apart from a simple wiring harness to the Rx and Battery. I will also cut out an air exit hole in the bottom of the fuselage to aid cooling. 1 Quote Link to comment Share on other sites More sharing options...
JOHN PENNY 1 Posted November 28, 2022 Share Posted November 28, 2022 Can I use my brushed motors with a3/1-3000 eco 11.1v lipo please. I am newbie to electrics Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 28, 2022 Share Posted November 28, 2022 Of course electricity is the same wherever it comes from. Quote Link to comment Share on other sites More sharing options...
JOHN PENNY 1 Posted November 28, 2022 Share Posted November 28, 2022 2 minutes ago, Paul De Tourtoulon said: Of course electricity is the same wherever it comes from. I just wondered if it was too much for motors and esc Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 28, 2022 Share Posted November 28, 2022 As long as the voltage is not any higher than the Esc and motor. Quote Link to comment Share on other sites More sharing options...
PatMc Posted November 28, 2022 Share Posted November 28, 2022 12 minutes ago, Paul De Tourtoulon said: Of course electricity is the same wherever it comes from. Nonsense ! Quote Link to comment Share on other sites More sharing options...
PatMc Posted November 28, 2022 Share Posted November 28, 2022 10 minutes ago, JOHN PENNY 1 said: I just wondered if it was too much for motors and esc It is. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 28, 2022 Share Posted November 28, 2022 (edited) 3 minutes ago, PatMc said: Nonsense ! Whether Nuclear, coal or green, it all works for me,,, still no mention of what brushed motors he is using, I had a couple of Graupner speed motors made for 12v, if that's what your is all about. Edited November 28, 2022 by Paul De Tourtoulon Quote Link to comment Share on other sites More sharing options...
PatMc Posted November 28, 2022 Share Posted November 28, 2022 2 minutes ago, Paul De Tourtoulon said: Whether Nuclear, coal or green, it all works for me,,, Very helpfull advice to a newbie. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 28, 2022 Share Posted November 28, 2022 John Excuse all the above comments. It all comes down to the rating of the brushed motor and its speed controller. For example if it was intended to be used on 6V (5s NiMh) then a 2s LiPo (8V fully charged) is likely to both overload the speed controller and shorten the life of the motor brushes significantly. What type and number of cells does it use at the moment? My first RC plane with a 540 brushed motor on 9.6V NiMh gave up after a few flights when run on a 3s LiPo. Substituted for an equivalent brushless motor and speed controller it is still going 9 years later Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 28, 2022 Share Posted November 28, 2022 I had the Robbe Concord, 8 x cad nickel = 9.6v I ran it on 3s 12v lipo, as Simon says, 6v = 2S lipo maximum. did you read this pat,,, As long as the voltage is not any higher than the Esc and motor. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted November 28, 2022 Share Posted November 28, 2022 1 hour ago, JOHN PENNY 1 said: Can I use my brushed motors with a3/1-3000 eco 11.1v lipo please. I am newbie to electrics You can but it will turn much quicker than on the normal 6cell Nimh cells they normally run on as the voltage is higher, and as power is basically rpm squared the amps go up too. So if it's prop'd for a 6 cell Nimh and you put a 3 cell lipo on you'll get lots more power, but maybe not for long, I did this on an old MPX Twinstar, it was great for a few flights until a motor burnt out! What motor and propellor are you using? a 2s Lipo might be a better option, unless you have a disciplined throttle thumb. Quote Link to comment Share on other sites More sharing options...
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