Michael, Indeed, NoAlOx or plain petroleum Jelly from the Pharmacy, it does not make much difference and that is why I went with the latter since it is cheaper. Solid metal is many thousands times more conductive than even the best "conductive" grease, since the grease is essentially an isolator with some fragments of zinc or similar metal sprinkled in. The reason they are marketed as conductive grease is that they help avoid corrosion of the metal they are appied on, due to the sacrificial nature of zinc, keeping the oxidation away from the metal that the zinc is contacting. This is the same purpose that your water heater has a zinc electrode in the water which is slowly consumed.
Please note that there is a difference between heat transfer and current transfer. For heat transfer you need intimate (compliant) contact and a heat transferring grease will help in the improvement of the transfer because air has a very bad heat transfer capability. For electric current transfer, grease makes no immediate difference and the contact may be pressure (cold) welded but battery connections need to be removable, so it can only be clamped on. The result is that of the surface, only the "tops" are touching while the "valleys" are not in contact and filled with grease to avoid oxidation. Grease is squeezed out with compression of the clamp until you reach the max compression force, thereby forcing the tops of the material into the opposing surface if the material is hard enough. That is why Alu *needs* a hard material as partner to make good contact: too soft material will not penetrate the Alu Oxide layer and therefor the contact is bad. It is virtual impossible to avoid AlOx to form when working in free air. Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Michael Ross Sent: Tuesday, January 14, 2014 9:41 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Dissimilar Metal Contact on LiFePO4 Battery Posts No, I'm not surprised and the leaching and tracking it around won't do much either. I have been sloppy saying grease and paste. A silver paste will do more. Not a grease at all. But really clamping force is the hot tip. So NoAlOx doesn't do much to improve conductivity. Or is that a misinterpretation? I can use some back up here. In electronics and elsewhere sometimes the silicon grease is a problem, it is bad around low voltage switch contacts for example; then the other conductive heat transfer pastes are good. Even here it is good clamping that is important, the layers of material is very thin and changes little. Really good clamping comes from smashing a transistor or IC between to pieces of metal, not using the little bolt hole and a screw. It is more important that the heat transfer material is compliant and touches a lot of surface on both sides. So you get conduction through something more substantial than air and tiny asperities. Maybe even peanut butter is better than nothing. I never found anything about how to use NoAlOx at the Ideal Industries website - can you direct me to that info? If you really really want to put two round conductors together a gas tight crimp is the way to go, It deforms the material and fuses it around any oxides. Don't they crimp those service wiring applications? Screw clamps like Polaris have always bothered me because you can stop short of getting the best connection. A high quality crimper is what you really need. I have my doubts about smearing anything on aluminum is going to stop oxidation. On Tue, Jan 14, 2014 at 12:22 PM, EVDL Administrator <[email protected]>wrote: > On 13 Jan 2014 at 21:06, Michael Ross wrote: > > > Why would anyone want to put an insulating paste in an electrical > > connection when a conductive material could be used instead? > > If you're talking about Noalox and its ilk, try sticking the probes of your > ohmmeter in a glob of that "conductive material" and see what you get. I > think you'll be surprised. > > Same deal, BTW, with computer processor heat and Artic Silver and its > imitators. > > I know, it seems intuitive - add highly heat-conductive metal to the > heatsink grease, and it should conduct heat faster, right? But when you > actually test it, as a computer hobbyist website did years ago, you find > that plain white silicone grease works just about as well, at a fraction of > the price. > > I wish I'd bookmarked that website; now I can't find it. > <tinfoil_hat>Maybe > that's because one of their advertisers suggested that such reports aren't > good for business.</tinfoil_hat> > > FInally, note how you're supposed to use Noalox and similar glop. You coat > the AL wire with it, WIREBRUSH THE WIRE, and then complete the connection. > The idea is that the abrasion removes aluminum oxide, and the Noalox > excludes air so new oxide won't form on the wire inside the connection. > > AL is very often used in electrical service entrance cable, and probably > millions of house main electrical panels have been installed that way with > no problems that I know of. > > David Roden - Akron, Ohio, USA > EVDL Administrator > > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > EVDL Information: http://www.evdl.org/help/ > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Note: mail sent to "evpost" and "etpost" addresses will not > reach me. To send a private message, please obtain my > email address from the webpage http://www.evdl.org/help/ . > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. 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