G-JIMG Posted October 12, 2018 Share Posted October 12, 2018 Whilst designing my first electric model, a King Air 350 Twin, I came across the issue of wire length between the ESC and the Battery. Tribal knowledge states that it must be kept as short as possible, otherwise the ESC will eventually fail. To mitigate against failure, capacitors should be inserted, "every few inches". However, I have been unable to find a definition of what constitutes a "long" wire or any details regarding the type, rating or distance of the capacitors. To find answers I went to the expert and contacted George at 4Max. His response was, "The long wires on ESCs used to be a problem, but most modern manufacturers have designed around this and now long wires are no longer a problem." So, who is right? Is there really still an issue with wire length or is the modelling community using out of date knowledge to solve a problem that no longer exists? Personally I'd go with George's view; he's been right about everything else I've ever asked him and I see no reason for him to be wrong now. What's the tribal view? Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted October 12, 2018 Share Posted October 12, 2018 I built and successfully flew the Depron Eurofighter sold on BMFA pages. Due to the design it needed approximately 9inches of battery to ESC wiring . Okay it was a 275 watt motor so not a great current pull but never had any problems. Is it the larger motors that create problems ?? Quote Link to comment Share on other sites More sharing options...
Nigel R Posted October 12, 2018 Share Posted October 12, 2018 George has given a very simple answer. In my view, it's not entirely correct. Take it with a pinch of salt. Also, define "long"... Anyway Caps work as a buffer against bad stuff happening to the ESC. Longer wires = more load on the caps. More load on caps = shorter life of caps. When the caps let go, the bad stuff starts happening to the ESC circuitry. Castle ESCs used to sell capacitor packs, they rated them against 'extra wire length' if I remember right. I will also say, good caps are expensive, and there are a lot of cheap ones around - so if you buy a cheap ESC, be aware that's one way for the manufacturer to make it cheap. How much extra wire length are you thinking of adding? Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted October 12, 2018 Author Share Posted October 12, 2018 Not according to George. The King Air will use two 800kv motors with approximately 18" of wire between each fuselage mounted battery and the nacelle mounted 45A ESC. According to him there will not be a problem with the wire length. Quote Link to comment Share on other sites More sharing options...
Barryorbik Posted October 12, 2018 Share Posted October 12, 2018 When the existing ESC cable lengths are insufficient, it is always better to extend the power input wires and keep the three motor wires as short as possible. The reasoning behind this is that extending the power input wires will, through losses in the extension cables, introduce additional resistance into the circuit, resulting in a slight reduction in the voltage and current available to the ESC but with 'reasonable' cable lengths and use of suitable cross-section extension cables, these can be made pretty insignificant. The three motor wires provide high frequency pulses to the motor windings and extending these could lead to increased electrical noise in the aircraft and in extreme cases, the additional inter-cable capacitance and resistance caused by the extended leads can cause motor timing or other issues. I hope this helps some but if you keep the power input wires to the ESC below 300mm you should be OK but always try to keep all of the ESC wires away from other internal wiring, to reduce the chance of introducing radiated electrical interference into the other systems within the aircraft. Barry Quote Link to comment Share on other sites More sharing options...
Nigel R Posted October 12, 2018 Share Posted October 12, 2018 Barry, the problem here is the induced voltage spikes at the battery side input to the ESC. It is not a resistance problem and the wire thickness has no effect. Always best to extend the motor wires. Switching noise is not a big issue with the FET controlled circuits, they are not like mechanical brushes are for creating broad spectrum noise. G-JIMG, I'd imagine you will get away with 18" OK. Personally I would look at adding a cap pack to that length. Or extend the motor wires to take up some of that distance if at all possible. cheers all Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted October 12, 2018 Share Posted October 12, 2018 Jim, This is absolute, contact George, take his advice as he will warrant the product he sells for the application you have discussed with him. Any other advice for another manufacturers product is not applicable in this case. ....I am off to the shed to fit a remote glow to my Laser... why bother listening to the manufacturer and expert if you just ignore them. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted October 12, 2018 Author Share Posted October 12, 2018 Chris, I always intended taking George's advice, as you say, they're his products and he stands behind them. I raised this topic because I'm new to the electric side of our hobby and was aware of conflicting views. Even in the 5 responses so far there's been advice to lengthen the motor wires and advice to lengthen the battery wires. I've asked George what has changed within the "modern" ESCs to overcome the problem, I'll post his reply when I get it. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted October 12, 2018 Share Posted October 12, 2018 Chris, you make a good point re: warranty. G-JIMG, this is an issue common to switched DC power transmission; the relevant design change is well established, bigger caps on the input. As said before, there are caps and then there are caps, so specifying correctly and purchasing ones that meet that spec both go toward that solution. TBH I don't think its worth you overthinking this one. You're not planning on using a massive extension. If George will warranty your clobber based on your install then move on! Edited By Nigel R on 12/10/2018 12:44:25 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 12, 2018 Share Posted October 12, 2018 If the manufacturer and retailler tells you that about his product that's fine. Follow the advice. As you say he will have to stand by it and he's probably right! However, my advice would be to not generalise this advice - or at least to only do so with caution. George is an expert with respect to his own products yes, but for the rest he's just "knowledgable and well informed" as indeed a lot of people are - including many on this forum. BEB Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted October 12, 2018 Author Share Posted October 12, 2018 Very good point BEB. George has confirmed that his ESCs will work perfectly well with 20" ESC to Battery wire lengths. Apparently the improved performance is down to the capacitors installed within the ESC and the fact that the power Triacs are now more resistant to spikes. However, as you rightly point out, his statement only applies to his product. Jim.G Quote Link to comment Share on other sites More sharing options...
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