I might well be fighting a losing battle, but for the price of 4 holes in a strip of material it has been a great education. Tonight I tested the different alloys of Al idea.
Last time, 0.02 x 1.75 in strip of roof flashing aluminum: ~120 F temperature rise in ~15 seconds, cross sectional area 0.036 in^2 Tonight: 0.1 in diameter aluminum welding filler rod ~30 F temperature rise in ~90 seconds, cross sectional area 0.016 in^2 I was rather impressed that < 1/2 the area had ~1/4 the temperature rise! My guess is the welding rod is a more conductive Al alloy than the roof flashing is the big difference. Sent: Sunday, September 21, 2014 at 11:03 AM From: "Chris Tromley" <ctrom...@gmail.com> To: evdragra...@email.com, "Electric Vehicle Discussion List" <ev@lists.evdl.org> Subject: Re: [EVDL] Dissimilar metals on Headyways? I think you're fighting a losing battle. Different alloys have an influence, but not enough to overcome the fact that copper has roughly twice the conductivity (both electrical and thermal) of aluminum. You'll need twice the cross-sectional area in aluminum as you would need with copper to achieve similar performance. Your 1.75 inch test shows a lack of proportionality, but that's likely due to short straps and how the current flows locally from the bolted joint. I'm thinking your best bet is to use copper conductors and be very sure all connections are thoroughly greased (Noalox, Vaseline, whatever) to ensure all moisture is excluded from the joint. And I would re-grease them once a year. Chris On Sun, Sep 21, 2014 at 2:54 AM, via EV <ev@lists.evdl.org> wrote:I thought folks would like to hear the results of some of my testing. 1/2 inch smashed copper pipe, 200 Amps for a 2S2P pack of 8 Ahr "P" (for Power") Headway cells: Things stayed cool. 1/2 inch by 0.02 inch braided strap with smashed copper pipe at connections: 5 F rise in 90 seconds at 200 A 1/2 inch by 0.01 inch Al: 200A, 80F to 200F in about 15 seconds! This was done in the oxidized state. 1/2 inch by 0.01 inch Al: 200A, 80F to 200F in about 15 seconds! This was done with sanding and immediate Noalox. 1.75 inch by 0.02 inch Al: 200A, 80F to 160F in about 30 seconds. The Al performed way worse than theory predicted, then I think I figured it out. Al roof flashing from Home Depot is apparently not a very conductive alloy of Al. I'd guess better Al would perform much closer to Cu. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub[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[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)
