Battery bus bars

I'd like to know more about whether any steel core ones are even out there. Still sounds weird to me.

 

I looked and could not find any. (Hardly proof that they don't exist though!) There were some with somewhat ambiguous descriptions, where in places the metal used in the nuts seemed to be for the bus bars, but later on it said they were copper alloy. Like this one:

(Darn! Every time the URL is placed here it is converted to an invisible MEDIA link. Search for B07XNNZ95Q on Amazon.com and look at the entry for $39.87 near the top.)

No surprise that the nuts which do not have flat bottoms have much higher resistance that do flat flange nuts. By eye it looks like the contact area would be reduced by about a factor of 20, and that's a best case, if the ridges on the bottom are all exactly the same height.

I would expect that in a comparison of the various copper based bars the ones which are flattest would have the lowest resistance, regardless of the exact alloy used. Bare copper would also have an advantage because it is softer than the nickel plate and would squish a little for maximum contact. (Ie, like the crush washers on the oil plug on a car.) Poorly made nickel plate could have a rough surface, and that would turn into a bunch of points contacting the bottom of a flat nut, rather than flat to flat.

 

Gotta be devious. If you make it a link yourself, the forum software leaves it alone then.

 

I would think the after market serrated lock nuts would prevent the nut from making a gas tight seal. When air gets in between the nut and bus bar the connection will oxidize, which increases resistance. Higher resistance makes heat, which will speed up the oxidation rate causing more resistance, and more heat ...

 

Yeah, I was too cheap to get new "good" nuts, & the old ones were too corroded to reuse. Didn't like the look of those serrations so I used a fine file to make the bottom face of the nuts mostly smooth. Seems to have worked.

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Yeah, I suppose that $0.88 per nut adds up, if you're buying 76 of them. (Though I guess for the lithium one, you'd only need about half as many?)

That said, I could still see myself paying it rather than sitting cross-legged with 76 nuts and a fine file. Ewww.

 

I was digging around quite a while trying to find replacements for the OEM nuts during my higher quantity building days. One I thought was interesting (and bought a box of 500) was a large flange nut that had a 10mm hex head instead of 8mm. The flange diameter was a near exact match for the diameter of the module stud base. The only problem was the 10mm head size created problems with the black plastic shields that install over the connections. I ended up buying a box of 1000 stainless nuts from a UK manufacturer that were fairly close to the oem, just slightly smaller diameter on the flange. I could never find the exact OEM nut anywhere except from Toyota. The best thing about building Gen 2 batteries using low mile Gen 4 batteries is that the nuts are normally in great condition and reusable.

 

I just happened to pick up some free spinning washer nuts and compared them to OEM. Auveco 16883

Height OEM 5mm vs 7mm
Washer diam 12mm vs 10mm
OEM washer is flatter 16883 has a concave profile, more tension when torqued?
Auveco Auveco Catalog 139

Belmetric version has a 12mm washer
Spin Nut Class 8 Steel Special - BelMetric

McMaster Carr version closest to OEM profile height 5.3 vs OEM 5mm
Nonmarring Locknuts with Spring-Lock Washer, Zinc-Plated Steel, M5 x 0.8 mm Thread | McMaster-Carr

 

How 'bout the crimp that keeps the washer on the nut? Does that kind of protrude?

Am I seeing that the Toyota nut made more of an effort to recess that crimp up into the washer, so it's not in the way when the nut is torqued down?

 

Crimp doesn't protrude.

 

But the Auveco washer is domed, right? How about when it's torqued down flat? Photo kind of makes the crimp look more possibly protruding, to my eye. But maybe the difference in washer diameter is playing tricks on my sense of scale.

 

Yes it is domed, the crimp is flat with the washer, when the nut is torqued and washer flattens the crimp is still flat with the washer. I think the McMaster Carr is the closest to OEM.

 

Or maybe TMR has already ordered and checked out the posted spin nuts. Also how does one order modules from TMR.

Replating the zinc coating on OEM nuts?

Electroplating System Tin Zinc - Tin Electroplating System Kit - Zinc Plating Polish (eastwood.com)

 

At the time I thought of it as a zen exercise (ohmmmm, stroke). Something to do while watching youtube and waiting for the modules to finish a discharge - charge cycle.

Plus I was too lazy to look up different replacements. Probably do it differently "next time", if there is one.

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Interesting feedback on the Auveco nuts. I can tighten the oem nuts by hand, then only takes a quarter turn of the torque wrench 48 in/lbs, with the Auveco its 1-2 turns of the torque wrench. Not keen on using those nuts, the washer is quite concave, the oem is nearly flat.

 

A devil's-advocate position might be that the deeper-domed Auveco washer, once tightened down flat, might exert a more consistent spring pressure over time.

I'm not sure what measurable difference it might make either way, but it might be something a person with a micro-ohmmeter could compare for the fun of it.

 

Ordered a 100 pack bus bar washer nuts from McMaster-Carr. $13 for 100 pack

https://www.mcmaster.com/91270A320/

Very close dome profile to OEM bus bar lock nuts. Washer diameter 12mm also.

 

I'd venture to say the OEM appears more flat because it's been torqued already. The new ones will also flatten out when installed and torqued. The Gen 3 and 4 get away from these style nuts and just go to flange nuts. Exact matches to the flange nuts used in the Gen 3 and 4 batteries seem to be impossible to find, (other than thru Toyota $$$$) but I've purchased a pack of 500 stainless steel flange nuts that have so far done a satisfactory job. The OEM flange diameter is slightly larger. I've also experimented with flange nuts that have a significantly larger diameter (slightly larger than the diameter of the terminal flange on the module, but they use a 10mm hex instead of 8mm, which causes problems with the black plastic shields. Since most batteries I build use Gen 4 modules, I'm typically able to use the Gen 4 fasteners since they're usually in excellent condition.

OEM Gen 1 and Gen 2: Washer is ~11.92 mm, expanded and flat
Gen 3 and Gen 4 flange nut is ~12.81 mm
The stainless nuts I've used are ~ 10.97 mm
The oversize nuts have flanges that are 14.7mm
The module terminal flange is ~13.5 mm

 

Glad this thread came back up... I just put a big pile of dirty OEM bus bars in the rock tumbler this afternoon and checked it just now and in there were some aftermarket bus bars made by Reflex Concepts, which is no longer in business. But I think when I bought them they might of been solid nickel, but may of been just nickel plated?

Anyways I got those out so now it's just solid copper tumbling, and the nickel bars look tarnished but no signs of different metal underneath unless the plating was stripped off entirely? Suspicious that they're plated and not solid nickel. How can I figure this out? A way to test them?