Woops, It appears that the source I referenced was wrong and the oxide itself *is* an insulator. Conductivity is apparently only not hampered by the fact that there will not be an oxide layer under the place where you clamped the alu solidly enough. Hmm, learn something every day...
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 Cor van de Water Sent: Monday, January 13, 2014 5:52 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Dissimilar Metal Contact on LiFePO4 Battery Posts Manfred, That is what I said: "Passivation layer" means that the material no longer reacts, because the alu metal is covered in non-reacting (passive) oxide. However, it says nothing about the conductivity and indeed, alu oxide is conductive - slightly less than alu but good enough to use the oxide-covered alu as a conductor. Lucily, because all our electric grid hangs together with (oxidized) alu cabling, especially the utility part. But I also discovered a modern microwave transformer wound with alu wire... 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 Manfred Bartz Sent: Monday, January 13, 2014 5:06 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Dissimilar Metal Contact on LiFePO4 Battery Posts Aluminium oxide is an insulator. http://en.wikipedia.org/wiki/Aluminium_oxide "Metallic aluminium is very reactive with atmospheric oxygen, and a thin passivation layer of aluminium oxide (4 nm thickness) forms on any exposed aluminium surface." The benefits of using NoAlOx may be more than just cutting through the thin oxide layer, the Zn particles would also tend to fill small gaps caused by imperfections in the surfaces of the parts being joined. Manfred On 14 January 2014 11:04, Lawrence Harris <[email protected]> wrote: > Just looked up NoAlOx. > > Improves service life of aluminum electrical applications > Reduces galling and seizing on aluminum conduit joints > Suspended zinc particles penetrate and cut aluminum oxide > > Seems it's not so much that the zinc makes it conductive as it helps break through the non conductive aluminium oxide layer and so improves the conductivity. So for aluminium connections it might be both useful and important to use something like this. For other situations (similar metals) just using petroleum jelly on a clean joint may work just as well; if the joint is tight enough the grease should be squeezed out and so does not interfere with conductivity only acts to exclude air and water reducing the potential for corrosion. > > While a dielectric is non conductive it does mean more than that, it's a property of an insulator and some have better dielectric properties than others. > > Lawrence > > On 2014-01-13, at 11:27 AM, Michael Ross wrote: > >> Dielectric essentially means non-conductive. The whole point of NoAlOx is >> to enhance conductivity and it contains zinc powder - some one said (I >> haven't looked into it much). >> >> Theoretically, why would you want to put a non-conductive material between >> two current carrying members, when a conductive grease would do just as >> well at protecting from moisture? I see no reason not to smear dielectric >> all around outside, but it might end up in the current path just the same. >> >> >> On Mon, Jan 13, 2014 at 10:49 AM, Hoegberg <[email protected]> wrote: >> >>> interesting >>> Noalox and Penetrox is not the normal dielectric?, >>> >>> so I would not use it on sensor plugs for example >>> >>> http://ecat.burndy.com/Comergent/burndy/product/PENA134 >>> >>> this seems to be zinc-fume/dust in thick non-petroleum grease and used for >>> joins with alu-alu or alu-copper. >>> >>> /John >>> >>> ---------------------------------------- >>>> From: [email protected] >>>> To: [email protected] >>>> Date: Fri, 10 Jan 2014 10:04:14 -0500 >>>> Subject: [EVDL] Dissimilar Metal Contact on LiFePO4 Battery Posts >>>> >>>> Hi Lee etc:I thought that stainless bolts would be a problem on >>> connections on the Cray-3 supercomputer I worked with Seymour Cray on in >>> Colorado Springs but the actual electrical connection is *not* through the >>> bolt but through the contact surfaces of the terminal top and strap (the >>> power supply was 2000A) - although it was in liquid flourinert - no >>> corrosion. All the LiFePO4 batteries sold T-Sky & CALB batteries have M8 >>> stainless bolts and copper straps supplied which are dissimilar metals with >>> the aluminum threads on the battery terminals. I haven't heard of >>> connection problems from those who actually drive their EV's 10K+ miles per >>> year but first sanding or wire brush them & adding Noalox-probably best or >>> dielectric grease to the contacts elleviates dissimilar metal galvanic >>> corrosion. I noticed that doing nothing in a wet east coast environment >>> leaves some white surface corrosion after 20k miles on the aluminum-copper >>> contact point. I ordered NORD lock washers & Noal >>>> ox from Grainger to redo all my connections with the stainless >>> bolts.Have a renewable energy day,mark in roanoke, VA www.REEVAdiy.org >>> >>> >>> >>>> From: Lee Hart <[email protected]> >>>> To: Electric Vehicle Discussion List <[email protected]> >>>> Subject: Re: [EVDL] Keeping LiFePO4 battery terminals tight every 10k >>>> miles >>>> Message-ID: <[email protected]> >>>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed >>>> >>>> Michael Ross wrote: >>>>> It is necessary to have a properly sized torque wrench, the willingness >>> to >>>>> look up the proper torque setting for the materials involved, and a >>> _______________________________________________ >>> 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. Ross >> (919) 550-2430 Land >> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone >> (919) 631-1451 Cell >> (919) 513-0418 Desk >> >> [email protected] >> <[email protected]> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140113/565e 65aa/attachment.htm> >> _______________________________________________ >> 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) >> > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140113/6f46 b291/attachment.htm> > _______________________________________________ > 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) > _______________________________________________ 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) _______________________________________________ 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) _______________________________________________ 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)
