Short stainless studs with an allen key head are not expensive. The problem with stainless machine screws is that they can allow damp into the terminal between aluminium and stainless although Ox-gard would be good there too. Loctite prevents that damp getting in. The allen key head means you can hold the stud steady with a key when tightening nuts. Those aluminium taps don't take a lot of use by the look of them and would be easy to strip so Loctite stabilises it. Sorry there is just the aluminium terminal rather than a second layer but if there is a washer needed in the stack then an aluminium washer would be good too.
I also used several layers of liquid insulation on the base of my aluminium cased cells (they are +vely charged). Every place the cells touch the case (and between them) there is a sheet of 0.5mm epoxy fibreglass. All blue wrapping (which is easily nicked exposing a hot aluminium case) has a covering of nylon mesh tape which binds the cells but also allows any heat to escape. And all electronic boards have several layers of Plastik-70 conformal coating.
Seems like a lifetime ago that I started this thread and got helpful advice like this.
It’s getting real now and so I am asking for some final suggestions before I buy my studs and get everything assembled.
Some updates on my end: my battery environment has a dirt floor which occassionally gets muddy during the rainy season, so not Marine, no salt, but worse than the typical basement or garage.
My main concern is avoiding any corrosion on the exposed threads of my grub screws. I’ll be locking them into place using either Loctite or JB Weld (more on that below) so I want to minimize the possibility of corrosion either between the exposed threads and the zinc-plated copper busbars and/or lugs, as well as any direct corrosion of the exposed threads from moist ambient air (such as white rust on zinc-plating).
I found these yellow-zinc-plated 6M grub screws and am thinking of going that route unless I need to worry about white rust:
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This would translate to sealed yellow-zinc-to-Aluminum within the terminal (Loctite or JB Weld) followed by yellow-zinc-coated-steel to grey-zinc-plated-copper at the busbars/lugs with some exposed yellow-zinc-coated steel and grey-zinc-plated copper in the ambient air.
Reading about ‘white rust’ of zinc is the primary concern causing me pause on this solution, but that seems to be mainly caused by salt and I am miles from the nearest salt water.
So I’d appreciate any inputs as to whether this yellow-zinc-plated grubscrew solution should work well in my sometimes-moist environment or whether there are issues I am overlooking.
I’ve also tracked down some slotted aluminum grub screws but they are slotted rather than hex, likely pricey, and I’m concerned corrosion of the exposed aluminum threads may be at least as great as concern of corrosion of exposed zinc-plated steel threads (though I’d appreciate any comments).
And finally, while I steered away from stainless due to increased concerns of galvanic corrosion, between eliminating concerns of galvanic corrosion within the stud by sealing with Loctite or JB Weld and now being equally or more concerned about environmental corrosion (rust) of the exposed threads in my sometimes-moist environment, the stainless threads should be best for preventing any environmental corrosion, so I’d appreciate opinions as to whether stainless may actually be the best option for my sealed-stud in a sometimes-moist application...
A quick update on what has changed on my end since I first started this thread:
Loctite versus JB Weld: the upper 3 threads of all of my cells are worn after merely three gently by-hand (w/ screwdriver) insertions and removals of the bundled stainless steel bolts.
In addition, I used a newly-purchased torque-wrench to tighten 8 cells to 4Nm / 35inch-lbs and stripped the upper 3 threads from one terminal.
The bundled 6M bolts appear to be slightly undersized and I can thread a separately-purchased M6 bolt into pretty much the full 5 threads of to thus ‘stripped’ terminals (4-3/4).
The lower 2 threads of all 16 of my cells are pristine / untouched, including the stripped terminal.
So I’m hopeful that I will be able to get an M6 grubscrew threaded into the stripped terminal in a way that will hold and because of the wear on the upper 3 threads of all terminals, I’m considering to use JB Weld to permanently-install grub screws into all terminals.
If the only advantage to Loctite over JB Weld is that the grub screw can be removed if needed, I’m leaning towards deciding I want these grub screws to be permanently mounted, especially if JB Weld results in a stronger attachment than Loctite and/or if it provides a better environmental seal as far as preventing against the possibility of galvanic corrosion and/or ‘rust’ within the terminal.
Finally, I’m ready to seal my battery within an environmentally-controlled container (temperature control, pumping through dry cooling air from outside when needed) if that is the only way to operate without concern in my sometimes-moist environment.
For those of you with experience in harsher environments than mine and who understand all of the metallurgical issues of operating in a (fresh / non-salty) sometimes-moist environment, I greatly appreciate any inputs on what you would choose to do facing my particular situation...
