Dielectric grease on cable lugs? Lets test!

[AntronX]

Inspired by this thread I decided to test it myself. I happened to have this big toroidal transformer core sitting on my desk that happens to be an excellent source of 400 Amps AC as high as my clamp meter will go. So I crimped two #4 lugs on 4 AWG welding cable, looped it through the core and bolted the lugs together torqued as high as I can do with two 12" socket wrenches in both hands. First Test is without grease I got 16mV drop across cable lugs at 349A = 0.0458mOhm of lug+contact resistance. Second test with grease applied I got same 16mV at 352A = 0.0455mOhm which is 0.9% less resistance than without grease. I think I tightened it a bit harder on that second try which could explain slightly better result. Grease use was CRC technical grade dialectric grease. Verdict: Applying grease has no effect on lug contact resistance.

EDIT: I forgot about the bolt providing additional continuity without grease on the lug > bolt > nut > lug interface. I will re-test using insulation washer. Here is Test 2 with nylon washer.

 

[#40Fan]

How about applying some "Project Farm" advanced weathering juice and retest after a couple of weeks.

YouTube Project Farm if you're not familiar with him.

 

[AntronX]

How about applying some "Project Farm" advanced weathering juice and retest after a couple of weeks.

Sure If someone will send me a sample i can do it.

 

[JRH]

How about applying some "Project Farm" advanced weathering juice and retest after a couple of weeks.

YouTube Project Farm if you're not familiar with him.

Project Farm guy is funny to watch… got more energy than 3 grey squirrels barkin at a cat.….he’s got good valid info on his tests too…His channel is definitely worthy of mention..

 

[Bluedog225]

Good info. I would be curious about the results a month or so after a salt water spray.

 

[Quattrohead]

Project Farm guy is funny to watch… got more energy than 3 grey squirrels barkin at a cat.….he’s got good valid info on his tests too…His channel is definitely worthy of mention..

This comment cracked me the fuck up oh my God lol

 

[Rednecktek]

How about applying some "Project Farm" advanced weathering juice and retest after a couple of weeks.

YouTube Project Farm if you're not familiar with him.

And then check the current difference on a winch when pulling the Farmabego out of the swamp. ?

 

[JRH]

Good info. I would be curious about the results a month or so after a salt water spray.

Didn’t say he was perfect , but haveing used much of what he tests for along time , he does some pretty good stuff and his results mirror much what I have found through the years on tools and different liquids.. especially about rust preventative..and fancy lubes…
some stuff we disagree on …. But not a lot… plus he doesn’t drop F bombs every 15 seconds trying to be a modern day talker … compared to most of utube the boy is pretty solid..

 

[JRH]

Good info. I would be curious about the results a month or so after a salt water spray.

He he be.. you’re right about rust… it is a beast to deal with … a true beast…

 

[webbbn]

Not exactly related, but the discussion of electricity and liquids reminded me of a somewhat odd method that we used back in the day to break in new brushes in new small electric motors (in this case used by RC racecars). Connect two wires, dip them in a cup of water, and hook them up to a battery.

The water provided the resistance and kept the motor cool, and also washed out the metal particles the would inevitably wear off. Just had to dry off the motor afterwards and put a few drops of oil on the newly broken-in brushes.

IMO, the more testing the better, so bravo!

 

[AntronX]

Here is second test with nylon washer to prevent any current from flowing through the bolt. First up is dry contact without grease. Got 16 mV at 335.5 A = 47.7 uOhm resistance. Next test with grease applied got 15 mV at 340 A at same exact setting on the Variac transformer. So I bumped up the voltage until I got 16 mV reading and got 367.4 A = 43.55 uOhm resistance which is 8.7% lower than without grease. This could be due to voltage error in my setup or clamping force difference but it's clear again that dielectric grease does not increase lug contact resistance.

 

[hwy17]

Awesome testing. Can you do one loosely bolted. Like just snugged. I'm curious about less tight connections (without dielectric), regarding DIY packs and the fear of snapping studs.

 

[AntronX]

Can you do one loosely bolted. Like just snugged.

Sure! Here is finger tightened and second one is barely holding. Not too different! 20 mV and 24 mV at similar currents.

 

[hwy17]

Sure! Here is finger tightened and second one is barely holding. Not too different! 20 mV and 24 mV at similar currents.

Thank you!

 

[rodrick]

Great info thanks for your efforts to bring us real world data

 

[Hedges]

First up is dry contact without grease. Got 16 mV at 335.5 A = 47.7 uOhm resistance. Next test with grease applied got 15 mV at 340 A at same exact setting on the Variac transformer. So I bumped up the voltage until I got 16 mV reading and got 367.4 A = 43.55 uOhm resistance which is 8.7% lower than without grease. This could be due to voltage error in my setup or clamping force difference but it's clear again that dielectric grease does not increase lug contact resistance.

At 16mV reading, I think the accuracy is +/-2.3mV, so about 14mV to 18mV

https://assets.fluke.com/manuals/77iv____umeng0000.pdf

You're near the limits what that meter can tell you.

Oh, and the clamp meter has plenty of digits, but looks like 2.8% accuracy. Swamped out by the counts of the voltage measurement.

https://assets.southwire.com/ImConvServlet/imconv/b1279be523eab6735b1d6918fc5748c45cf9da35/origin?assetDescr=21050T%20Spec%20Sheet

Those accuracy numbers are probably over environment and time, so should be better for short-term comparison.

 

[glandpuck]

I apply dielectric grease on all of my outdoor MC4 solar connectors.

On FLA battery terminals where corrosion can occur and battery acid build up, I apply Kopr Kote.

 

[AntronX]

At 16mV reading, I think the accuracy is +/-2.3mV, so about 14mV to 18mV

You're near the limits what that meter can tell you.

That's why I dialed the Variac until I got same 16mV at different tests. I guess the meter may not be absolutely accurate but relative accuracy between tests should be good enough.

 

[JRH]

This comment cracked me the fuck up oh my God lol

Yep…..They are funny little critters…?

 

[zcskywire2]

With this showing up on my feed at the right time I thought I would repeat the testing here with some more accurate gear that I have at the office

Setup consists of the following
B&K 9115 DC PSU set at 30V 30A
Keysight 34465A bench multimeter
TE 1.5kw 1ohm resistor


I measured across a set of 1/4in 2awg lugs bolted together hand tight. The multimeter was set to the maximum read time for the highest precision. Results were the average of at least 50 readings. First readings were done with out grease. The second set was done after applying a healthy amount of DeoxIT L260CP copper particle grease. Hardware was allowed to cool off fully between readings.


I saw an drop of 7.580mV average without any grease applied with a note able amount of variance across the readings.



Moving to the greased set we saw both much lower variance and average resistance also dropped to 0.987mV an over 7.5x reduction in resistance


As a slight follow up I confirmed the original no grease run by degreasing the connections and running them again