Lee, Those metals are elastic up to a point, and all behave according to Young's Modulus. If you don't exceed the yield strength, then they DO NOT experience permanent deformation.
There is no lead involved with the large and small format Li cells that I have seen and the aluminum and copper will not cold flow unless the bolts are tightened too much, the bulk metal won't compress then, but the threads will strip. Regarding lead, it also behaves by Young's Modulus, but has a very low yield strength. If you don't exceed the yield strength it will be as good as steel. However the clamping force may be too low. Temperature does not significantly effect elasticity of metals, as long as you don't melt them. You do have account for differences in thermal expansion when the joint has huge changes in temperature. Then you need a higher torque. Bottom line - use the right fasteners, clean surfaces, no rubber or plastic washers, torque them correctly, and there will be no loss of clamping force. I agree copper directly onto aluminum is a bad choice. Proper plating is how to get by. You don't get a galvanic couple when you plate. For example good chrome on steel is a three layer process steel, polished, is plated with copper to provide a barrier and good surface for adhesion of the nickel layer and then chrome on top. Corrosion couples require moisture. If you put them together dry you can get away with a lot, but dry is really hard to maintain, with overnight changes of 30F degrees in humid conditions you get condensation. The other factor is large differences in electronegativity (galvanic potential) of the jointed touching metals. If they are far apart in galvanic potential you have more trouble. Copper and zinc, copper and nickel, copper and tin not so bad. Copper and aluminum sucks. SS in aluminum is not too bad. I expect no problems from that. Aluminum is kind an odd beast because it is not really what we see on the surface but instead the oxide of aluminum. Here is a chart: http://www.roymech.co.uk/Useful_Tables/Corrosion/Cor_bi_met.html I like the format but the info is hazy. Is brass a copper or zinc alloy? Here it is for all elements sorted by electronegativity: http://www.lenntech.com/periodic-chart-elements/electronegativity.htm Anyway a flat, tight, dry joint will stay that way and not corrode. I can see where a grease would come in handy to keep moisture away. I don't think this has much to do with torquing however. On Mon, Jan 6, 2014 at 1:35 PM, Lee Hart <leeah...@earthlink.net> wrote: > Mark Hanson wrote: > >> ... I found a few other battery terminal bolts not tight after 20k >> >> miles (even with sealing paint on terminal bolts CALB 130). >> So it's best to tighten terminal bolts on lithiums every 10k miles it >> seems. I used to tighten terminal bolts on old lead GC batteries >> >> every 500 miles but didn't think it was necessary with lithiums but >> apparently they need it as well just less often. >> > > Soft metals like lead, aluminum, and copper can "cold flow" due to > pressure. Temperature cycling and vibration also play a part. > > Unfortunately, these factors are common in electrical connections. These > soft metals are used for their high electrical conductivity. High currents > make the temperature extremes worse due to self-heating. > > Dis-similar metals are another factor. These create corrosion couples, > that corrode if the joint isn't absolutely air tight. They expand at > different rates with temperature, leading to large pressure changes in the > joint. Inexperienced or cheapskate designers seem to have a total disregard > for the metals used in their electrical contacts. They ignore 100 years of > experience and use whatever metals are handy. > > My guess is that if (for example) you bolt a copper strip to an aluminum > stud with a stainless steel screw, it's hopeless to expect a reliable > connection. > -- > "Obsolete" means nothing more than "the salesmen would prefer you buy > something else." -- Dave McGuire > -- > Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.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) > > -- 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. 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