Nylon lock nuts on battery cells?

[michaelplogue]

Would it be a good or bad idea to use lock nuts with nylon inserts on BMI\PSI\Lifebatt type cells? I'd like something that I was sure would not come loose from vibrations. Would I be better off using regular nuts and spring/locking washers?

.

 

[oofnik]

I would say metal nuts with lock washers would be best. You'll get more surface area for current flow and reduce the chances of heating at the terminals.

 

[Malcolm]

I'd also be interested to hear if anyone reckons this is not a good idea, as I've used nylock nuts on my lifebatt cells. There are also copper washers and bronze spring washers underneath each nut. There's nowt like belt and braces...

The nuts do put a fair amount of torque on the studs as you tighten them, but it's not excessive.

I did have one nut seize on one of the aluminium studs as I was undoing it, but I think that may have been my fault for using a used nylock nut. The nylon liner may have been damaged.

 

[AndyH]

Would it be a good or bad idea to use lock nuts with nylon inserts on BMI\PSI\Lifebatt type cells? I'd like something that I was sure would not come loose from vibrations. Would I be better off using regular nuts and spring/locking washers?

.

Michael, I would think it would depend on how much torque is required to spin the nut on the stud. It might make it challenging to measure the proper torque when tightening - especially on the aluminum terminal. PSI recommends 6.9 in lb or .78nm for the nuts. The stud is square inside the cell's end cap, so you're not going to spin the stud.

If you have a batch of nuts that have very high locking force, you could spin them onto a standard 6M1 bolt first to loosen them a bit. There will still be plenty of locking action if the nuts are spun on a few times.

I don't believe surface area is an issue since the nylon lock is an 'add-on' to the nut - the area of the threaded portion and the area of the nut face should be similar when comparing a standard nut with a nylock.

If you're going to use nylocks, you don't need the lock washers.

 

[scoot]

What do the BMI studs appear to be made of? I'm guessing Aluminum at this point... Perhaps I read that somewhere else around here. If it is Aluminum then I would think most nylon material is softer, unless it is a glass filled nylon in which case it would be very abrasive/gripping towards even steel. I don''t know what they put in most nylock nuts. Maybe the clean torque setting standard approach with previously known materials would be the most tried and proven here... not an expert... just raising the possibility. If you would like i could ask Slakinater Dann about it?

 

[boostjuice]

What do the BMI studs appear to be made of? I'm guessing Aluminum at this point... Perhaps I read that somewhere else around here. If it is Aluminum then I would think most nylon material is softer, unless it is a glass filled nylon in which case it would be very abrasive/gripping towards even steel. I don''t know what they put in most nylock nuts. Maybe the clean torque setting standard approach with previously known materials would be the most tried and proven here... not an expert... just raising the possibility. If you would like i could ask Slakinater Dann about it?

The M6 Anode stud is made of alluminium and is more prone to snapping than the nickel coated steel cathode stud. They would be much stronger if they werent centrally drilled and tapped for internal jelly roll nickel/alluminium tab attachment, but thats just the way the design is.

Andy is right about nylocks being suitable as an alternative to a spring washer configuration. You can 'wear-in' nylock nuts by threading them onto a spare M6 bolt which cuts/compresses the nylon segment to a slightly looser fit of the bolt thread. This means the torque needed to thread them onto the cell studs is certainly less than the max torque spec and wont risk snapping the studs.

Images courtesy of AndyH;

http://www.endless-sphere.com/forums/download/file.php?id=23516&mode=view

 

[Toorbough ULL-Zeveigh]

i think your nuts should be castellated.

 

[michaelplogue]

i think your nuts should be castellated.

What if I still want to have children some day......?

 

[scoot]

hee hee, yep I had had to look it up... and then realized it was for real.

But on a serious note, I have used these slotted lock nuts on steel threads before and they worked great for that. When new, they really grip hard onto the threads (much tighter than nylock nuts) which gives me pause when considering using them on aluminum studs. I am pretty sure, actually quite sure that they would damage the aluminum threads.

Please let us know how you eventually decide to go Michael. I may end up going with the BMI cells as well and would very much like to know the best way to go about it. So far, based on the feedback here it seems like the nylocks are the way to go.

 

[Malcolm]

Still not sure if Turbo was serious or not, but I'd definitely advise against using castellated nuts on the aluminium studs. Castellating your nuts would be irreversible.

 

[Toorbough ULL-Zeveigh]

Castellating your nuts would be irreversible.

so michaelplogue, freez em now if yoos gots em!
oh, i guess that second sentence relates to the first, not simply a general observation?

it's been a long while since i've worked with slot nuts so my memory could be hazy with time.
but for the smaller gauge bolts i don't recall them being remarkably tighter than a nyloc.
could be there's a variety in tolerance between different manufacturers?
an initial 'wear-in' on a steel bolt might work on these too.
definitely would want to try one out for myself tho.

every battery produces heat to some degree, so i would tend to favour an all metal fastener.
one that wouldn't soften, deform or perhaps eventually melt with periodic exposure to higher temps the way nylon might.
just thought i'd throw another hat in the ring.

 

[scoot]

These latest comments make a great deal of sense to me. My recent experience with 10 mm "locking" slotted nuts from Mcmaster Carr is that upon initial use they were extremely tight and in that "first use condition" unsutible for the aluminum threads. After removing and refitting them on a steel stud numerous times (perhaps 10 times) they broke in enough such that they behaved very similarly to nylock nuts in regards to tightness. Sounds like this may be good way to go. Should be easy enough to break them in on a steel stud/bolt with a deep socket and drill. And I would guess for this application removing and refitting "broken in nuts" numerous times on the BMI studs could kept to a minumum with enough planning and forthought. I know there is another joke or play on words in there somewhere :lol:

 

[scoot]

BTW, the nuts I am referring to are called "expanding locknuts" and are cadmium plated steel Mcmaster Carr part # 94235A110... they are rather expensive at $1.85 each. Thay also have a stainless version (94560A100) at $3.47 each.

 

[boostjuice]

BTW, the nuts I am referring to are called "expanding locknuts" and are cadmium plated steel Mcmaster Carr part # 94235A110... they are rather expensive at $1.85 each. Thay also have a stainless version (94560A100) at $3.47 each.

I hope you mean Nickel plated steel. Cadmium is toxic $#!T...

 

[scoot]

Ah yes, licking them in not recommended. :lol: Sorry couldn't help myself.

BTW correction on previous post I was using the M6 (10 mm head nuts)... different part number obviously. and that's the BMI stud size I think.

 

[AndyH]

My frame of reference for different lock nuts is primarily from the light aviation world. For an aircraft, you must use solid metal lock nuts, castellated nuts with cotter pins, or drilled and safety-wired fasteners under the cowl. Most small airplanes are pulled thru the air with 4- and 6-cylinder horizontally-opposed air cooled engines that look like they'd be more comfortable in the back of a VW bug. Cylinder head temperatures are about 350 to 400ºF but most of the air under the cowl is cooler.

By comparison, the 40138 cells shouldn't get hotter than 60ºC, about 140ºF in use.

Yes, Scoot - the PSI/BMI/LiFeBatt cells all use 6M1 studs. Aluminum 'positive', steel 'negative'.

I think an 'exercised' nylock would be a great match. An all metal lock nut might be workable on the steel stud, but I would expect it would wear away at the aluminum stud. Maybe they're both fine if the pack is going to be bolted up for final assembly.

 

[scoot]

That sounds very reasonable and logical to me Andy. Thank you for your insight.

 

[AndyH]

A few minutes searching gave a temperature range for Nylocks. The best I found are rated to 220ºC The least capable were 'only' good to 140ºF. I'm thinking we're in pretty good shape here!

These 18-8 stainless nylocks from McMaster-Carr are good to 250ºF and cost $8.80 per 100 pieces.

 

[michaelplogue]

Thanks for all of the input guys! I think I'm going to go with the Nylocks. I figure if my temperature rises enough for them to melt, I'd already be in a whole-heap-of-hurt, and I'd be well beyond worrying about my nuts coming loose.......

 

[BMI]

Yes, Scoot - the PSI/BMI/LiFeBatt cells all use 6M1 studs. Aluminum 'positive', steel 'negative'.

Hi Guys. Just to clear a misconception up. Yes the positive terminal of the 40138F1 cells is aluminium but the negative terminal is definitely not steel! (I guess I am here to clear these things up)
The negative terminal is in fact copper but is nickel plated to prevent oxidation so it looks like it is steel. If you have an old/defective cell cut into the stud with a hacksaw or file it slightly and you will see the copper underneath. This is still the stronger terminal when fastening nuts since the aluminium stud is more likely to break if over tightened. Both studs are hollow and not solid which is why they are quite easy to break off if over tightened.

 

[scoot]

Yes, Scoot - the PSI/BMI/LiFeBatt cells all use 6M1 studs. Aluminum 'positive', steel 'negative'.

Hi Guys. Just to clear a misconception up. Yes the positive terminal of the 40138F1 cells is aluminium but the negative terminal is definitely not steel! (I guess I am here to clear these things up)
The negative terminal is in fact copper but is nickel plated to prevent oxidation so it looks like it is steel. If you have an old/defective cell cut into the stud with a hacksaw or file it slightly and you will see the copper underneath. This is still the stronger terminal when fastening nuts since the aluminium stud is more likely to break if over tightened. Both studs are hollow and not solid which is why they are quite easy to break off if over tightened.

So what would BMI's specifications for nuts/washers be? Do you have any recomendations regarding "lock nuts" of any kind and what torque setting to use with them?

 

[BMI]

Yes, Scoot - the PSI/BMI/LiFeBatt cells all use 6M1 studs. Aluminum 'positive', steel 'negative'.

Hi Guys. Just to clear a misconception up. Yes the positive terminal of the 40138F1 cells is aluminium but the negative terminal is definitely not steel! (I guess I am here to clear these things up)
The negative terminal is in fact copper but is nickel plated to prevent oxidation so it looks like it is steel. If you have an old/defective cell cut into the stud with a hacksaw or file it slightly and you will see the copper underneath. This is still the stronger terminal when fastening nuts since the aluminium stud is more likely to break if over tightened. Both studs are hollow and not solid which is why they are quite easy to break off if over tightened.

So what would BMI's specifications for nuts/washers be? Do you have any recomendations regarding "lock nuts" of any kind and what torque setting to use with them?

AndyH has previously provided the correct information regarding tightening of the cell nuts. The factory simply uses a regular split/spring washer and nut but nylock nuts or similar vibration resistant nuts will be just as suitable.