So we have : battery terminals are from aluminum , over them we have laser welded STEEL stub with the nut from steel and we connect zinc covered copper bus bars .
The possible poor connection I have seen is between bus bar and very small size of the stub from the battery that is 1mm wide .
can we use a special conductive paste the ensure better conductivity and 10 years of corrosion free for the contact ? I don’t think WD40 is designed for this, it is too liquid and evaporate.
what are your thoughts about this ?
Your concerns are quite legitimate, in my experience.
WD40 is definitely not approprate to improve conductivity. It is good a good lubricant for cutting and tapping aluminum, but not as a coating between conductors.
My cells, at my request, came with the 6mm threaded terminal holes. After much consideration, and minor struggles with two (out of 48) terminal threads being loose, I now affix all of the studs into the threads with epoxy adhesive. I am pleased with the performance of that solution.
Subsequently, over several months, I had minor trouble with “high” resistance connections between terminals and bus bars. In most applications this “high“ resistance would not be discernible, but because we monitor cell voltage to 1 mv of resolution with the BMS, we can easily detect it as "cell" voltage deviation. I eliminated those variations by carefully cleaning contact surfaces with a Scotch-Brite pad, wiping with acetone, and applying a super-thin coating of MG Chemicals “Silver Conductive Paste” to the terminal contact surface. The silver paste looks expensive for a tiny tube, but that tiny tube will last me a LONG time. Only a fly spec amount, spread with a rubber-gloved finger, is needed for each terminal, and it is working great!
Others will suggest here that the silver paste is foolishly expensive, but I doubt if they have tried it. Personally. I do not at all like No-Alox, or other “conductive grease” for this application. One great thing about being a DIY-er is that you can pick your own preferred solution.
BTW, the bus bars are tin plated, rather than zinc plated.