Paul De Tourtoulon Posted November 20 Share Posted November 20 Hi all, I have just changed another press button switch on my 4s powered geared starter, it is used extensively by me and other members of the club for 15cc to 30cc ic engines, the button contactor on the end of it lasts around 6 months, and then it just solders itself so it won't stop, it feeds the relay on the other end of the starter, is there some magic electronic component like a condenser, Capacitor or one of those shoky things ( rc cars over here use them)that would help to stop the arcing of the switch ?. thanks Paul Quote Link to comment Share on other sites More sharing options...
steve too Posted November 20 Share Posted November 20 The first thing that I would try is a diode in parallel with the relay. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 20 Share Posted November 20 Put a capacitor across the switch it should supress any sparking that causes the contacts to weld. Dont ask me what size etc . Perhaps a sparky on here can suggest ? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 20 Author Share Posted November 20 So would a diode stop the sparks ,, Thanks like you, what capacity ?,,, Thanks I will experiment both of your ideas tomorrow,,, Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted November 20 Share Posted November 20 The push button on mine is of a simple and cheap design, I'll have a think about a solid state switching device. Clearly I would need to always unplug it from the lipo (some very small current drain), but I do that before putting it away at the end of a session anyway. Mine has no relay, just battery, switch and motor on the starter + IMO its the extra current from the Lipo that causes the contact wear, not the arc when the switch is released as the motor is off load by then. Quote Link to comment Share on other sites More sharing options...
steve too Posted November 20 Share Posted November 20 27 minutes ago, Paul De Tourtoulon said: So would a diode stop the sparks https://en.m.wikipedia.org/wiki/Flyback_diode Quote Link to comment Share on other sites More sharing options...
Nigel R Posted November 20 Share Posted November 20 (edited) 1 hour ago, Chris Walby said: extra current from the Lipo that causes the contact wear, not the arc when Unless the current is melting the contacts then I would be fairly sure the wear is from arcing, plus Paul is switching a coil not a motor, different strokes. 100nF or 1uF ought to do for a relay coil. Does depend in the relay though. Just looking for something to damp things down until the Diode takes over and clamps. Diode, nothing fancy, 1n4007 maybe, a standard rectifier type. Put both next to the switch. Edited November 20 by Nigel R Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted November 20 Share Posted November 20 (edited) 1 hour ago, steve too said: https://en.m.wikipedia.org/wiki/Flyback_diode So explain why when the starters are operated from lead acid batteries or 3S lipo the contacts don't weld up but do with 4S lipos. IMO Its not a flyback voltage issue, its the additional applied voltage and lower internal resistance of the lipo that generates higher current that the contacts are not rated for or were designed for. What's the C rating of a lead acid battery compared with a Lipo, a magnitude difference on a near stalled motor? These switches are a couple of bent bits of metal. Edited November 20 by Chris Walby 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted November 20 Share Posted November 20 (edited) Car starters use a different mechanism (solenoid) from either of the above situations, and they absolutely can weld up although it is less likely. Edited November 20 by Nigel R Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted November 20 Share Posted November 20 7 minutes ago, Nigel R said: Car starters use a different mechanism (solenoid) from either of the above situations, and they absolutely can weld up although it is less likely. I am not going to argue with you, as you are just plain wrong. In the last 10 years how many starter motors do you know that have failed with their contacts closed? Anyone ever had a car starter motor solenoid weld its contacts closed? Quote Link to comment Share on other sites More sharing options...
steve too Posted November 20 Share Posted November 20 4 hours ago, Engine Doctor said: Put a capacitor across the switch it should supress any sparking that causes the contacts to weld IIRC, when putting a cap across a switch it should be in series with a small resistor. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 20 Share Posted November 20 Standard practice across contacts switching inductive loads in my BT days. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 21 Share Posted November 21 14 hours ago, Chris Walby said: I am not going to argue with you, as you are just plain wrong. In the last 10 years how many starter motors do you know that have failed with their contacts closed? Anyone ever had a car starter motor solenoid weld its contacts closed? Yes but not when fitted to a car. I was trying to making a battery tab welder using a couple of large capacitors charged ftom a 12v battery then triggered by a foot switch via a starter dolenoid. Worked for short while then welded the solenoid contacts together ? I gave up then and bought a tab welder on line. Quote Link to comment Share on other sites More sharing options...
Dickw Posted November 21 Share Posted November 21 3 minutes ago, Engine Doctor said: Yes but not when fitted to a car. I was trying to making a battery tab welder using a couple of large capacitors charged ftom a 12v battery then triggered by a foot switch via a starter dolenoid. Worked for short while then welded the solenoid contacts together ? I gave up then and bought a tab welder on line. Well you did build it to be a welder 😁 Dick 1 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted November 21 Share Posted November 21 (edited) 18 hours ago, Chris Walby said: IMO Its not a flyback voltage issue, its the additional applied voltage and lower internal resistance of the lipo that generates higher current that the contacts are not rated for or were designed for. Current switched through a motor which is inductive in nature, leads to what exactly, when the switch is closed/opened? Sparking. I am not going to argue with you, as you are just plain wrong. 17 hours ago, Chris Walby said: Anyone ever had a car starter motor solenoid weld its contacts closed? Ford Fiesta, about 20 years ago, needed an occasional whack with the hammer to free up. Car wasn't worth sorting it properly. I guess that doesn't count as it's not within the last 10 years? Edited November 21 by Nigel R Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted November 21 Share Posted November 21 High current contactors require an RC snubber network - you could give one of these a try on the starter https://uk.rs-online.com/web/p/circuit-breaker-accessories/2778526?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_ePMax_Prio1_RSPro-_--_-2778526&matchtype=&&gad_source=1&gclid=Cj0KCQiA0fu5BhDQARIsAMXUBOI1QW8t2NurilhjC6S2v70wfhT_72yHflu74cby2LFgbW_S0ZPt5isaAhfjEALw_wcB&gclsrc=aw.ds Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 21 Author Share Posted November 21 (edited) Thanks for your replies, what about this ?. https://fr.aliexpress.com/item/32944554113.html Or more like this, I only have to find what values to use,,,https://www.mouser.fr/new/cornell-dubilier/cde-qas-film-capacitors/#Bullet-3 Edited November 21 by Paul De Tourtoulon mouser Quote Link to comment Share on other sites More sharing options...
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