# Mechanical Wire Lugs



## PTCruisin (Nov 19, 2009)

Just wondering if anyone has used mechanical wire lugs in lieu of crimped connectors in their EV wiring.

We recently had a Horiba dynamometer installed here at the school and all the high current/voltage connections are made with mechanical wire lugs, with 3/0 and 2/0 wiring.

It seems to me that proper termination of the fine-stranded wires (wrap them with a thin copper shim) would prevent the splaying of the wires are they are being compressed in the mechanical lug. It also seems to make sense to use wire glands when passing wires through a bulkhead or junction box wall, and then securing the wires with a mechanical lug.

I believe that Netgain Controls uses this scheme in their controllers but I can't confirm since I don't own one.

Any thoughts or comments?


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## dragonsgate (May 19, 2012)

You will not get as tight a fit on the wires as a good crimp plus you will have two threaded connections that can loosen up from heating and cooling. Also extra crannies for dirt and corrosion to get into.


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## Zappo (Sep 1, 2011)

Yeah, these are fine for regular THHN wire but I wouldn't use them with welding cable even with the copper shim.


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## DIYguy (Sep 18, 2008)

They work just fine. They are used on all high power electrical systems. The difference is that the wire in these cases use less strands. (because they don't need to flex) As u mentioned, wrap the finer conductors with copper. The other thing is to observe the mating surface. . . I've seen some that are not machined smooth. This is more of an issue with lower voltage I think. The disadvantage is that they are bulky, awkward shape. The advantage is that you can remove them. 
Also make sure the conductor is of adequate size for the lug. If it's too small, the dome set screw goes too deep, loosing much of it's threaded connection.


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## major (Apr 4, 2008)

In a lot of cases you're adding a dissimilar metal into an already troublesome assembly. I've used these in the lab. They can be convenient. But I try to avoid them on permanent or competition installations.


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## DIYguy (Sep 18, 2008)

major said:


> In a lot of cases you're adding a dissimilar metal into an already troublesome assembly. I've used these in the lab. They can be convenient. But I try to avoid them on permanent or competition installations.


Hey Major. You mean the dissimilar metal being Aluminum? The same aluminum you connect to on the top of the batteries?? 


Edit; PS, I don't usually use them either....


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## major (Apr 4, 2008)

DIYguy said:


> Hey Major. You mean the dissimilar metal being Aluminum? The same aluminum you connect to on the top of the batteries??


You note I said "in a lot of cases". You're right; sometimes you do connect Cu to Al. But I think the other cell terminal is Cu. And motor terminals and controller terminals and fuses and such are not Al in most cases.


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## DIYguy (Sep 18, 2008)

major said:


> You note I said "in a lot of cases". You're right; sometimes you do connect Cu to Al. But I think the other cell terminal is Cu. And motor terminals and controller terminals and fuses and such are not Al in most cases.


Ya, I hear you. That said, if you look in the industrial world of panel building for automation (a gazillion panels in a gazillion factories around the world.) You will find these or similar. . connecting copper wire to terminations points. Way way way more than anything else. That said, I don't use them typically either. I just wanted to clear up the "they won't work" thing. Most industrial breakers, fuse holders etc, also use a built in version of this same idea.


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## PTCruisin (Nov 19, 2009)

DIYguy said:


> They work just fine. They are used on all high power electrical systems. The difference is that the wire in these cases use less strands. (because they don't need to flex) As u mentioned, wrap the finer conductors with copper. The other thing is to observe the mating surface. . . I've seen some that are not machined smooth. This is more of an issue with lower voltage I think. The disadvantage is that they are bulky, awkward shape. The advantage is that you can remove them.
> Also make sure the conductor is of adequate size for the lug. If it's too small, the dome set screw goes too deep, loosing much of it's threaded connection.


Thanks for validating what I suspected. I figured if they are being used in industrial applications they had some merit. I am considering using them in a design that would enclose 2 contractors, fuse, and hall effect current sensor in a box with input and output ports using wire glands to pass the stripped conductors through to mechanical lugs attached to buss bar. 

I am using crimped lugs now and have no issues but I want to experiment with these mechanical lugs.


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## Zappo (Sep 1, 2011)

DIYguy said:


> Ya, I hear you. That said, if you look in the industrial world of panel building for automation (a gazillion panels in a gazillion factories around the world.) You will find these or similar. . connecting copper wire to terminations points. Way way way more than anything else. That said, I don't use them typically either. I just wanted to clear up the "they won't work" thing. Most industrial breakers, fuse holders etc, also use a built in version of this same idea.


Actually, no one said they won't work. They just won't work as well. I am an industrial maintenance manager. Before that, I was an electrical supervisor. In the last 30 years I think I've personally used about a gazillion of these myself. The only way I've seen it work well with fine wire (like welding cable) is to crimp a barrel on it first. Wrapping with a copper sheet works, but not well. We have many of our panels checked annually with a FLIR thermographic camera. The few terminations we have that are done that way with fine wire cable are always running hotter and need tightening more often.


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## Ziggythewiz (May 16, 2010)

Not to mention most industrial applications are likely stationary.


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## Sunking (Aug 10, 2009)

I can tell you from 30+ years of working with Telecom battery plants, *NEVER EVER USE* any mechanical lugs for anything. In my industry it would get you banned for life if you did. You are just begging for a failure and fire.

We only allow UL listed irreversible 2-hole compression terminals using 15 ton hydraulic crimping tools. or exothermic welding for all grounding and bus bar terminations.


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## PTCruisin (Nov 19, 2009)

Sunking said:


> I can tell you from 30+ years of working with Telecom battery plants, *NEVER EVER USE* any mechanical lugs for anything. In my industry it would get you banned for life if you did. You are just begging for a failure and fire.
> 
> We only allow UL listed irreversible 2-hole compression terminals using 15 ton hydraulic crimping tools. or exothermic welding for all grounding and bus bar terminations.


OK. Point well made. But please explain the failure mechanism.


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## Zappo (Sep 1, 2011)

PTCruisin said:


> OK. Point well made. But please explain the failure mechanism.


I think Dragonsgate summed it up pretty well in post #2 to you. Mainly, these just won't bite into and capture the finer wire very well. Wrapping them helps but is kinda like a band aid.


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## Sunking (Aug 10, 2009)

PTCruisin said:


> OK. Point well made. But please explain the failure mechanism.


OK but I thought that was obvious. 

A fully encircled compression termianl fuses the wire strands together with the compression terminal making it a homogenous mass that has lower resistance vs soldering and far superior lower resistance than a mechanical pressure connector. It also makes invulnerable to vibration failure. 

When used with a conductive oxygen inhibitor like NO-OX-ID Special makes it immune to corrosion by sealing out all air, moisture, and contaminants. 

The bond is so strong, a wire or cable will fail from tension test and real life before the termination will fail. You cannot pull the terminal off the wire or cable it is terminated too.

Point to be made here is when you use exra-flexible wires (finer Strand) you have to use compression terminals made for them. They have longer barrels and require an extra crimp or two.


LONG BARREL 1/0 AWG for Flex Cable


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## EVfun (Mar 14, 2010)

I gotta agree with him here. I use quality lugs designed to be double crimped. I can attach the terminal to a rafter by the bolt hole and hang all my weight on the 2/0 cable. It holds me securely. I cut the terminal apart in the crimp and could see the tiny individual copper strands where no longer round from being compressed together.


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## swoozle (Nov 13, 2011)

I ask because there is some difference here I'm not catching:
Why are these high-current industrial connectors ok? They have set screw compression and foil shims to wrap around the cable and the marketing specifically mentions welding applications.







http://www.leviton.com/OA_HTML/SectionDisplay.jsp?section=40474&minisite=10251
"Leviton Single Pole Cam-Type Devices are designed to provide superior service and durability, even under the most severe operating conditions. Our 18 Series Single Pole Ball Nose Cam-Type Devices are rated to 400 Amps, and are typically used in the broadcasting and welding industries."

I first saw these on EVTV. I'm using one as a maintenance disconnect and don't plan on changing it. But I am curious how it reconciles with the industrial practices you folks describe.

Thanks


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## major (Apr 4, 2008)

swoozle said:


> Why are these high-current industrial connectors ok?


ok? Yep, there are different types of connectors which are ok. Those are very nice. Perhaps some of the best non-crimp units available. Compared to the crimp style, they would be more expensive, larger and, to some degree, less reliable. But they would likely work perfectly well for you.

Not everybody has the 15 ton hydraulic crimp tool. I have an 8 ton unit. With the proper dies and lugs and 2 crimps per lug, it does the job. I do a lot of cable assemblies. This is the best solution for me. You need to find a solution which fits you situation. If you rely on a mechanically secured lug, then you had better check it regularly.

Regards,

major


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## dragonsgate (May 19, 2012)

PTCruisin said:


> Just wondering if anyone has used mechanical wire lugs in lieu of crimped connectors in their EV wiring.
> 
> We recently had a Horiba dynamometer installed here at the school and all the high current/voltage connections are made with mechanical wire lugs, with 3/0 and 2/0 wiring.
> 
> ...


The wires running from my house to the meter fit into a hole and crimped down with a set screw very much like the set screw shown in your picture. The wires in that cable are fewer and much thicker than the strands in welding cable. About 10 years after I built my house I had some electrical problems in the form of getting readings of 135 volts on my 110 outlets. I found out that the setscrew connections at the meter had loosened up over the years. There was no vibration or flexing. It was simply resistance caused by expansion and contraction from heat and cold loosening the connection. You will not get that from a good crimp. I did my cable crimps on a hydraulic hose crimping machine. My NAPA store builds hoses for farm tractors and the like and he had the right fitting to do the job. I think it was for ¾ hose. I was lucky that we are good friends and he let me do them myself. Even if he charge a couple dollars a crimp it would be worth it for the neat tight fit. Sometimes the shot cut winds up being the longest and thus the cheapest the most expensive.


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## Sunking (Aug 10, 2009)

major said:


> Not everybody has the 15 ton hydraulic crimp tool. I have an 8 ton unit.


8-ton lever units are good up to 2/0 AWG. However most electrical supply houses rent crimpers, or you can take them to a cable shop for termination. 

Proper wire termination is one of the most critical factors for both performance and more important life safety. Poor terminations start fires period.


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## PTCruisin (Nov 19, 2009)

Sunking said:


> OK but I thought that was obvious.
> 
> A fully encircled compression termianl fuses the wire strands together with the compression terminal making it a homogenous mass that has lower resistance vs soldering and far superior lower resistance than a mechanical pressure connector. It also makes invulnerable to vibration failure.
> 
> ...


Thanks. You have convinced me to back away from using the mechanical lugs.

When I built my first EV, I went to great pains to get reliable crimps on all my cables and they have performed as expected. I guess I was looking for a less labor intensive, more modular solution as I plan my second conversion.

I used a local mine equipment repair shop with a large hydraulic crimper on the first conversion so I am going to take the new cables to them.


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## ruckus (Apr 15, 2009)

Zappo said:


> ...We have many of our panels checked annually with a FLIR thermographic camera. The few terminations we have that are done that way with fine wire cable are always running hotter and need tightening more often.


Good post. Thermal camera does not lie. That is proof that crimp connections are superior. 

I have a good quality mechanical crimper that is like a giant bolt-cutter with dies that spin in the head. Any opinions from the pros as to whether these are substandard to the hydro crimpers? I double-crimped the 4/0 wire with noalox. Looked really super dooper...

p.s. where is the best/cheapest supply of those long-barrel lugs?


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## Zappo (Sep 1, 2011)

ruckus said:


> Good post. Thermal camera does not lie. That is proof that crimp connections are superior.
> 
> I have a good quality mechanical crimper that is like a giant bolt-cutter with dies that spin in the head. Any opinions from the pros as to whether these are substandard to the hydro crimpers? I double-crimped the 4/0 wire with noalox. Looked really super dooper...
> 
> p.s. where is the best/cheapest supply of those long-barrel lugs?


Thank you Ruckus. Although I don't believe that any mechanical crimpers are quite as good as hydraulic, they can do a perfectly acceptable job. I used a set of T&B ratcheting crimpers (with the interchangeable dies an LONG handles) for mine and feel they are just fine. 

We have a relatively cheap FLIR camera at work. If it ever stops raining, I want to take some shots of my batteries and cable after running hard for a while. I've ran an IR temp gun around the pack and never found any hot spots. I'm just curious the pictures with the FLIR will look like.


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## Sunking (Aug 10, 2009)

dragonsgate said:


> About 10 years after I built my house I had some electrical problems in the form of getting readings of 135 volts on my 110 outlets.


Common problem and it is caused by loose connection on the neutral aka grounded service conductor. It did not cause all your outlets to go to 135 volts, just half of them. The other half were were low around 100 to 105 volts.


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## Sunking (Aug 10, 2009)

Zappo said:


> Although I don't believe that any mechanical crimpers are quite as good as hydraulic, they can do a perfectly acceptable job.


Almost true but not entirely accurate. The 6 and 8 ton mechanical levers are just as good, but on the smaller gauges up to about 1/0 with 6 ton units, and 2/0 on 8 ton units. 

With most of the 6 and 8 ton units it takes two crimps to equal 1 full crimp because they are 1/2 sized dies. The hydralic 14 and 15 ton units take any where from 1 to 4 crimps depending on the size of the conductor and length of the barrel. 

TBM 6








TBM 8








TBM 14 Hydraulic


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## Nabla_Operator (Aug 5, 2011)

*Re: Mechanical Wire Lugs (some theory)*

The failure mechanism that you asked for, PTCruisin, is called PRE-TENSION. 



In fact: Lack of pre-tension in the threaded connection of the (industrial) mechanical lug. 

Pre-tension is needed more in cars than in industrial application because of thermal expansion (temperature range of -20 to +90 degrees Celsius) and micro vibrations that make the many fine strands displace over each other, after a while. 



The strands have to be clamped together with a spring-loaded item. 














I hope these sketches are helpful



paul-


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## dragonsgate (May 19, 2012)

Sunking said:


> Common problem and it is caused by loose connection on the neutral aka grounded service conductor. It did not cause all your outlets to go to 135 volts, just half of them. The other half were were low around 100 to 105 volts.


Yes you are right. I just didn’t want to get too wordy. I realized the problem after my car charger burned out. 
Luckily nothing else got wrecked.


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## dragonsgate (May 19, 2012)

*Re: Mechanical Wire Lugs (some theory)*



Nabla_Operator said:


> I hope these sketches are helpful
> paul-


I found the drawing very informative. Thanks


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## PTCruisin (Nov 19, 2009)

*Re: Mechanical Wire Lugs (some theory)*



Nabla_Operator said:


> The failure mechanism that you asked for, PTCruisin, is called PRE-TENSION.
> 
> 
> In fact: Lack of pre-tension in the threaded connection of the (industrial) mechanical lug.
> ...


Excellent post. Thanks Paul.


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## ruckus (Apr 15, 2009)

Those sketches are great!


This can be summed up as: "Yo bro, that sheet needs to be teeight!"


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## DIYguy (Sep 18, 2008)

swoozle said:


> I ask because there is some difference here I'm not catching:
> Why are these high-current industrial connectors ok? They have set screw compression and foil shims to wrap around the cable and the marketing specifically mentions welding applications.
> View attachment 14958
> 
> ...


OK, everyone is entitled to their own opinion and u can use any connectors u want. So far two issues have been raised, one is the dissimilar metals issue, the other is the means by which mechanical force is applied and maintained. 

So, you will get dissimilar metal issue regardless what you use unless u use both aluminum and copper connectors. I haven't seen issues regarding this in my experiences anyways.

As for the crimp/force mechanism, it doesn't matter much what method is used as long as it is adequate and maintained. The lug doesn't know if it was a "hammer on", hand crimp or hydraulic crimp or dome set screw. 

I didn't think we were comparing credentials or job titles however, I worked in a tier1 automotive plant for 26 years as Technologist, Engineer and Engineering Manager. The plant was over 1 million square feet had several hundred manual weld stations and several hundred robotic weld stations. We did thermography also and found the most useful information from it was for distribution bus ducts and roof imaging for breakdown. At any rate, the connector mentioned above is commonly called a cam lock or twist lock. We used thousands of them. The most common ones are made by Tweeco and Dinse (Europe). There are others Bernard for example, which I don't think makes them anymore. Anyways, these are made for and used on the welding cables you all use in your EV's. They are, bar none, the best "removable" connector on the market. They use one or two dome set screws with or without copper foil (the main reason for this is due to the fine strands wanting to spread). Most industrial welders operate at voltages much below that of an EV. If you want to talk about vibration and heat, I can guarantee you some applications in a factory that will put an EV much lower on the scale. So, do they work? Yup. Do they use a dome set screw? yup. 

Don't get me wrong, I use crimp lugs in 99% of applications also. That said, I have several battery boxes with cam lock disconnects and bulk head connectors for several years now. I've never had to re-tighten them. They show no signs of heating with my temp gun. You can have a poor install with set screws that show heat. . . just the same as u can with crimp lugs.

BTW, I've also seen some very thin crimp connectors that I would not use due to thin wall and questionable ability to maintain force, post crimp.

Here's a pic of the receptacle side on one of my boxes. 

Yes, no, maybe so. . . .


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## Zappo (Sep 1, 2011)

DIYguy,

You are absolutely right that the cam-type fittings are a great way to terminate welding cables. The Leviton cam-type are even used for higher voltages than welders. Our 480V 350KVA diesel generator connects to our UPS with these. They work very well. I seriously considered using them as part of a quick connect system for my pack.

You can't possibly be arguing that these:








can be compared to these:








Are you?

They are not made for fine wire. I know a lot of things we do don't follow NEC rules, but this is one we might want to watch out for. The attached pdf file is an article written specifically for solar installations but it fits here too. For those that don't want to read the full article (with pictures of some lug failures even), here is one excerpt:

UL engineers have said that few 
(if any) of the normal screw-type mechanical terminals 
that the PV industry commonly uses have been listed 
for use with ﬁne stranded wires. the terminal must be 
marked or labeled speciﬁcally for use with ﬁne-stranded 
conductors [see NEC 110.3(A) and (B)].
View attachment IAEI-1to2-05.pdf


I'm not trying to argue or tout my "industrial credentials". I'm just trying to supply information so people can make informed decisions. BTW, the article also supports exactly what you were saying about inferior crimp terminals too.


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## swoozle (Nov 13, 2011)

DIYguy said:


> .....I didn't think we were comparing credentials or job titles however, I worked in a tier1 automotive plant for 26 years as Technologist, Engineer and Engineering Manager....


Don't know why you chose to bring that up after quoting my full post, because I certainly didn't whip out the ruler to see who's is longer.

Facts, experience and theory stand on their own without a care for (and sometimes in spite of) the credentials of the speaker. I asked a clarifying question (this ain't my thread) to learn why THIS type of set screw cable termination was generally considered acceptable when THAT one was not. In all of the information being shared it seems to come down to specific subtleties of design and reliability expectations.


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## Zappo (Sep 1, 2011)

Swoozle,

I don't think that comment was aimed at you. Both Sunking and I mentioned our backgrounds in our posts. I'm guessing that came off as insulting to him somehow. I can't speak for Sunking, but I only meant for it to provide perspective. I'm truly sorry if it came off sounding like I'm a "know-it-all". That is so not me. I just feel that everyone has a right to my opinion.


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## DIYguy (Sep 18, 2008)

swoozle said:


> Don't know why you chose to bring that up after quoting my full post, because I certainly didn't whip out the ruler to see who's is longer.
> 
> Facts, experience and theory stand on their own without a care for (and sometimes in spite of) the credentials of the speaker. I asked a clarifying question (this ain't my thread) to learn why THIS type of set screw cable termination was generally considered acceptable when THAT one was not. In all of the information being shared it seems to come down to specific subtleties of design and reliability expectations.


No no, sorry. I just used your post to reference the twist lock connector. My bad.... I can clean that up if u like.


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## DIYguy (Sep 18, 2008)

Zappo said:


> DIYguy,
> The Leviton cam-type are even used for higher voltages than welders.


My point was to indicate how they are used for lower voltages, (which is tougher for voltage drop) not higher voltages. . . that is why I referenced it.



Zappo said:


> You can't possibly be arguing that these:
> View attachment 15026
> 
> 
> ...


Sure. Why is it not? U happened to go and get a double set cam lock. The original one posted was a single. That's ok. The dome set is exactly the same in both, interchangeable. 




Zappo said:


> They are not made for fine wire.


Ok, so help me understand this. They both have a hole for the conductor and both exert force with the same dome set. How is one made for fine wire and the other not? (It's true that this is the respective application most of the time, I agree with that)




Zappo said:


> I know a lot of things we do don't follow NEC rules.


Nuff said. All those gazillion panels/connectors you and I both mentioned were approved by an authority in our respective countries/locals, or you wouldn't be using them.



Zappo said:


> I'm not trying to argue or tout my "industrial credentials".


Why bring it up then?

One of the things I don't like about the smaller aluminum terminals is that you need to put a wrench on them in order to hold them well enough to torque the set. With the cam locks, especially the double set ones, you can actually hold on to them (or step on them ) when setting. 

Anyways, I'm won't bother stretching this out any longer. Additionally, I'm not suggesting set screw lugs are better. . . only to dispel the comments that they will not work. 
BTW, you will notice that the standard "electrical supply crimp lugs" are not well matched in size to the respective welding cable . . very tight fit. The "welding supply" lugs fit much better. Even this has a bearing on crimp quality. 

Here is a small tip that I find helpful regardless of what lug/terminal used, when u don't have copper foil. Rather than check the wire insertion depth, then cut the insulation and fight to get it all in the hole. . . (recall welding cable vs electrical supply lug). . try this. . . Mark the length of the insulation required to be removed . . then cut only about 1/4" max of it off the end. Next make a cut all the way around the mark for full insertion, but don't remove it. Now you are left with a bit of a "collar" of insulation. This collar holds the wire together pretty well. Now you can start the lug without making a mess. Once the lug is started, you can carefully, cut along the length of the loose bit to remove it. . . and push the lug the rest of the way.


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## dragonsgate (May 19, 2012)

I have always wondered about the accepted Anderson connectors with two pieces if metal pressed together by a little bit of pressure from a flat spring. How much resistance occurs there? It makes some of the cam locks look pretty good. As for credentials and who knows the most it is all relevant. 
It is sometimes hard getting ideas across on time delay written form like this much less argue. I only have an associate’s degree in art but if you want to argue Art History I can piss pretty far up the wall. We should all keep or egos in or pockets.


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## DIYguy (Sep 18, 2008)

dragonsgate said:


> I have always wondered about the accepted Anderson connectors with two pieces if metal pressed together by a little bit of pressure from a flat spring. How much resistance occurs there? It makes some of the cam locks look pretty good. As for credentials and who knows the most it is all relevant.
> It is sometimes hard getting ideas across on time delay written form like this much less argue. I only have an associate’s degree in art but if you want to argue Art History I can piss pretty far up the wall. We should all keep or egos in or pockets.


Yes, Andersons are used a lot and u r right, there is no comparison to a cam lock. We had fleet of electric lift trucks at one point and there was a pile (literally) of Anderson connectors in the mechanics bay. That said, they did get unplugged while powered a lot... lol 
I can't piss as far as I once could. . . but I can once-piss as far as I ever could.... lmao


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## major (Apr 4, 2008)

dragonsgate said:


> I have always wondered about the accepted Anderson connectors with two pieces if metal pressed together by a little bit of pressure from a flat spring.


I've been abusing Anderson Power Products connectors for 20 years and continue to be impressed with the functionality and reliability


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