Erfolg Posted May 28, 2009 Share Posted May 28, 2009 I have set up my battery lead with an overall length of 19 (from terminals of lipo to connction onto the board)", so far it has worked OK. Yey I think I have read that long leads can cause a failure. Is this length excessive? The shorest I could go is 14", which obviosly requires some additional work, being lazy, I feel is best avoided. Erfolg Quote Link to comment Share on other sites More sharing options...
Robert Bromwich Posted May 28, 2009 Share Posted May 28, 2009 hi Erfolg If u can make them shorter without to much messing around then i myself would think about doing it as there is less chance of the conductors inside breaking and less resistance as they are short cables Dont know if there is a set max length just make them as short as u can that all u can do Rob Quote Link to comment Share on other sites More sharing options...
Ben Mullins Posted May 28, 2009 Share Posted May 28, 2009 I would have thought the longer the cable the less power you're gunna get at the buisness end. Wouldn't think it has much of an effect at this stage, compared to phone wires etc. However, I have read that you wanna keep the Motor to ESC wires short coz of all the pulses etc that the ESC uses. Maybe you could just trial and error and tell us all what happens Ben Quote Link to comment Share on other sites More sharing options...
Andy Harris Posted May 29, 2009 Share Posted May 29, 2009 I2R (I squared R) could become an issue, beefy cables will help. If you are pulling say 20A then that is 400xR which could be 0.1ohm, or 40W loss in the cable. That 40W will go as heat. If you have 0.01ohm thats 4W, not so bad in the mix of things. Andy Quote Link to comment Share on other sites More sharing options...
Sparks Posted May 29, 2009 Share Posted May 29, 2009 Hi Erflog, Extending battery lead length will increase voltage spikes at the ESC due to inductance of the cable. I took some oscilloscope traces to see the effect of 300mm battery/ESC cable length (I'd post an image of the traces but can't figure how to do it!). At 10 amps, the ESC commutation voltage spikes were 0.88Vpk/pk at the battery +ve terminal and 2.7V pk/pk at the ESC +ve terminal. Taken to extreme, this could damage the ESC electronics. The other effect is to increase interference, which can desensitise your receiver (more so on 35MHz). To overcome this, you can fit an Electrolytic capacitor across the supply lines at the junction point of the extended cables. Any capacitance between 220uF to 1000uF will do the trick, with appropriate working voltage - a low ESR (Equivalent Series Resistance) capacitor will be more effective. You should be able to get one from the usual outlets (Maplin, Farnell etc) regards, Richard Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted May 29, 2009 Share Posted May 29, 2009 Too long battery wires will kill controller over time, voltage spikes will be higher than battery voltage, bad for components and will give noise interference, input caps will get hot and will explode.Battery wire inductance is the main problem here, and to a much lesser extent, wire resistance. ALL ESC manufacturers say the same: extend motor wires, not battery wires. If you cannot but extend battery wires: solutions, rules of thumb, ESCmanufacturer statements, installation, diy & commercial solutions, tech background info:: http://www.rcgroups.com/forums/showthread.php?t=952523&highlight=kill @Richard Low ESR-type caps are a must, must, tandard el-caps will get hot due to I²R losses in caps. High spikey currents in there. Prettig weekend RonEdited By Ron van Sommeren on 29/05/2009 18:48:20 Quote Link to comment Share on other sites More sharing options...
Erfolg Posted June 1, 2009 Author Share Posted June 1, 2009 Ron Thanks for the information. What is particularly useful is theat the motor wires should be extended not the battery wires. I made a poor decession, by making assuming that I would get more spikes from the motor and was and to a large extent ignorant of what really matters. I will now extend the motor leads by about 50mm max. Andy & Sparks Although the maths is very easy, what is not easy for people like me, is what the answer means or implies. If known to you, a value range which is deemed acceptable, above which increases concern, would enable people such as myselt with little practical electrical experience to make a value judgement. Perhaps a short contribution to a magazine, an essay on the "technical requirements for sucessfull installation of electric flight packages" completewith the formulas for inductance etc, a few simple typical calcs and the meaning and implications of the values obtained. Would be useful. It could put the "E" back into RCM&E! Erfolg Quote Link to comment Share on other sites More sharing options...
Ron van Sommeren Posted June 1, 2009 Share Posted June 1, 2009 Motor current is rather smooth because on the motor side of the controller, the (motor)induction actually does a good job at removing spikes/pulses.There induction is something good. See this graph: http://www.consult-g2.com/course.html -> www.consult-g2.com -> chapter 9: electronic controllers -> fig 9.2 PWM representation Vriendelijke groeten Ron Quote Link to comment Share on other sites More sharing options...
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