Crimp Quality…?

[JRH]

Does anyone know or is there a way to test the quality of your crimp…?
i have about 70 to do this week for the wiring up my system, 4 ga to 4/0.
im using good quality everything , have practiced it a lot and have cut about 20 of the practice lugs in half to check the cold weld status .. I am trying to do it as good as possible ,but after you do them ,how do you really know, ( unless it’s an obvious screw up) ..I do a pull test , they look fine, but how do you know.?

is there a way to use a multi meter to evaluate resistance ( ( OHMS) before and after of the wire and lugs and whatever difference may exist before joining and after joining…

or is that even a meaningful test…

so much could show up as so many things with just one bad crimp being the culprit…

this ain’t cool…
there has to be a way to know more than just hoping it’s a good crimp..
But maybe I’m wrong…
thx ….Jim

 

[timselectric]

Do a sacrificial crimp and cut it in half. If you can see gaps, or the individual strands. It's not good enough.

 

[MrThisIsME]

I will put my flame suit on, but following this path for years.

If I was super concerned about quality on larger crimps (say 0 gauge and larger). I would first ensure I am using a trusted hydraulic crimper with AWG dies (not mm). Than crimp it. I leave about 3/8" of the copper wire exposed from the lug. Than fill the remaining portion of the lug with solder. Clean up the lug and use good (right sized) shrink wrap with adhesive in it.

 

[JRH]

Do a sacrificial crimp and cut it in half. If you can see gaps, or the individual strands. It's not good enough.

Thank you Tim , I have done 20 test cuts ,as I said ,they are looking pretty good consistently now . I even bought some pre made big wire online 1/0 to 4/0 to cut theirs into( ouch$$ ) mine were as good or better
it seems ..and that in itself is why I’m not buying them pre cut..

from my test some are perfect and the next two are not as good…none appear bad now but this is like voodoo stuff. You can’t know unless you cut it , but if you cut it you cant use it…
I hate unknown stuff…

i cannot not be alone in this question…

Jim.

 

[toms]

Accurately measure (with a micrometer) the distance across the flats of the crimp.

For any given cable / crimp combination there is a specification for crimp measurement.

You need to get the measurements from the supplier of your cable and crimp.

You can cut one to have a look, but that is only an indicator of your method - the next one might not be as good.

It’s not rocket science, measuring across the crimp is all you need to do.

 

[JRH]

I will put my flame suit on, but following this path for years.

If I was super concerned about quality on larger crimps (say 0 gauge and larger). I would first ensure I am using a trusted hydraulic crimper with AWG dies (not mm). Than crimp it. I leave about 3/8" of the copper wire exposed from the lug. Than fill the remaining portion of the lug with solder. Clean up the lug and use good (right sized) shrink wrap with adhesive in it.

Thank you for taking the time to answer…anyone who has a flame suit must be a busy camper…wish I had one…
this is the next step in my build and it seems to be the most unverifiable of all the challenges…
I hate unquantifiable stuff…
I will consider what you say…
thank you jim.

 

[OzSolar]

No you are not alone. A simple ohm test with a standard DVM will only be a pass/fail so not that helpful. Meggers only test the insulation strength (I believe) so they aren't that helpful either.

For me the test is to make all of the connections, take the the system up to 100% of it rating, hold it there then meticulously test the voltage drop across each connection. Anything that seems out of line needs to be addressed. EG. .3 v x 100 amps = 30 watts. That may not be a big deal across the entire system but across one breaker or connection... eeh.

 

[JRH]

Accurately measure (with a micrometer) the distance across the flats of the crimp.

For any given cable / crimp combination there is a specification for crimp measurement.

You need to get the measurements from the supplier of your cable and crimp.

You can cut one to have a look, but that is only an indicator of your method - the next one might not be as good.

It’s not rocket science, measuring across the crimp is all you need to do.

Interesting … haven’t heard of that…I will investigate. hmmmm
thank you toms…
Jim.

 

[JRH]

No you are not alone. A simple ohm test with a standard DVM will only be a pass/fail so not that helpful. Meggers only test the insulation strength (I believe) so they aren't that helpful either.

For me the test is to make all of the connections, take the the system up to 100% of it rating, hold it there then meticulously test the voltage drop across each connection. Anything that seems out of line needs to be addressed. EG. .3 v x 100 amps = 30 watts. That may not be a big deal across the entire system but across one breaker or connection... eeh.

Yea.. I keep seeing .2 ohms show up in all of the pseudo testing I have done on the joints I have done and tested tonite…
I’m using a pretty decent meter( Klein CL900) and im testing the wire before I crimp and then the whole assembly afterwards … I’m finding the same number. .2 …..

in my world of a non- electrical guy, that means I’m either doing OK or I am missing somthing big time..

I am going the whole 9 yards in initial prep of all the component parts and joints and cutting no corners , but it’s weird for the end product to be so unknown Until after your done building it..

but thank you…
Jim.

 

[JRH]

I thank all of you guys for your advice ..I’m Gona have a few drinks ,a steak and lay down and think about it all.
J.

 

[RVLiFe]

I understand your plight. I am currently in the process of remaking all my connections. Not because they are necessarily bad but simply because of the fact that I know more now then I did when I made them and I have a hard time sleeping at night without questioning my perfection (or lack there of). Between your Ohm tests and throwing a infrared thermometer on it, your probably just fine but please don’t let that stop you from retightening everything down every so often just to be sure. Surprising how loose connections can get after a few months of just sitting there. Also, one thing I always do now is to go one wire size larger then what the project calls for. This will also help compensate for a poorly made connection or resistance that you didn’t know you had.

 

[MrThisIsME]

I thank all of you guys for your advice ..I’m Gona have a few drinks ,a steak and lay down and think about it all.
J.

And listen to "Pink isn't well he's back in the hotel?"

 

[JRH]

And listen to "Pink isn't well he's back in the hotel?"

Haaa

 

[JRH]

I understand your plight. I am currently in the process of remaking all my connections. Not because they are necessarily bad but simply because of the fact that I know more now then I did when I made them and I have a hard time sleeping at night without questioning my perfection (or lack there of). Between your Ohm tests and throwing a infrared thermometer on it, your probably just fine but please don’t let that stop you from retightening everything down every so often just to be sure. Surprising how loose connections can get after a few months of just sitting there. Also, one thing I always do now is to go one wire size larger then what the project calls for. This will also help compensate for a poorly made connection or resistance that you didn’t know you had.

Yes I understand the Vulcan mindset… I do have a thermal thermometer but it’s only good after it’s done and current is flowing .. I will consider that the .02 ohms is at least a benchmark to shoot for . If a connection reads more then I must have somthing amiss Unless it’s very long… Don’t worry about wire gauge , About 90% of the wire I bought is 3 to 4 times the size of what’s required .. I have a thing for overkill in everything …
Thanks you for your thoughts…
Jim.

 

[OzSolar]

Yea.. I keep seeing .2 ohms show up in all of the pseudo testing I have done on the joints I have done and tested tonite…
I’m using a pretty decent meter( Klein CL900) and im testing the wire before I crimp and then the whole assembly afterwards … I’m finding the same number. .2 …..

in my world of a non- electrical guy, that means I’m either doing OK or I am missing somthing big time..

I am going the whole 9 yards in initial prep of all the component parts and joints and cutting no corners , but it’s weird for the end product to be so unknown Until after your done building it..

but thank you…
Jim.

You're welcome. Nothing is going to replace testing the system at full load when it's all installed so if it was me that's where I would spend my time and money testing things. Enjoy your steak.

 

[John Frum]

Does anyone know or is there a way to test the quality of your crimp…?
i have about 70 to do this week for the wiring up my system, 4 ga to 4/0.
im using good quality everything , have practiced it a lot and have cut about 20 of the practice lugs in half to check the cold weld status .. I am trying to do it as good as possible ,but after you do them ,how do you really know, ( unless it’s an obvious screw up) ..I do a pull test , they look fine, but how do you know.?

is there a way to use a multi meter to evaluate resistance ( ( OHMS) before and after of the wire and lugs and whatever difference may exist before joining and after joining…

or is that even a meaningful test…

so much could show up as so many things with just one bad crimp being the culprit…

this ain’t cool…
there has to be a way to know more than just hoping it’s a good crimp..
But maybe I’m wrong…
thx ….Jim

4/0 copper can handle 320 service amps in free air.
That is 400 fault amps.
Instead of bracket racing you are going to learn in the division where parachutes are mandatory.

 

[JRH]

4/0 copper can handle 320 service amps in free air.
That is 400 fault amps.
Instead of bracket racing you are going to learn in the division where parachutes are mandatory.

That’s well said… that took thought… when you havent walked this path before each step is a challenge .. gota be cautious.. second time you can jog it.. third time you sprint… I will get there and in good fashion too.

I have watched your comments for a while….there’s a lot of value in them. thanks for your input……

jim.

 

[Vigo]

You can't accurately test any high-current connection with a regular multimeter by measuring ohms.

The reason is that most multimeters, even good ones, will generally only read down to 0.2ohms even when you touch the meter leads directly to each other. You can think of this as the resistance of the leads and internal circuit of the multimeter. Unfortunately this is not a helpful number other than to point out a glaring failure. It doesn't tell you 'how good' a connection is. A good connection for a high current circuit will be in the low hundredths of ohms or in the thousandths of ohms aka milliohms.

It's useful to think about the role of resistance in voltage drop and heat buildup. Voltage drop across a connection is equal to the ohms of the connection X the amps flowing through it. So if for example you DID have a 0.2ohm connection and were flowing 100a across it, it would drop TWENTY volts! Enough to cause your inverter to go into low-voltage shutdown if it were on the battery circuit. 0.02ohms would get you 2 volt drop in that scenario, and that's survivable but not ideal. So you can see how small the ohm number would be for a 'near perfect' connection.

Unwanted resistance in connection converts electrical potential into heat. To quantify that is also pretty simple: it's just watt's law. Watts = Volts X Amps. So our 20v, 100a situation would lead to 2000w of heating at that connection. If it DIDN'T shut down the inverter it would quickly lead to a fire. The 0.02ohm connection which dropped 2 volts would only lead to 2x100=200w of heating, which would still be too hot to touch and might melt the insulation off the wire depending on how large of a piece of material it's occurring in and how quickly it can conduct that heat away from the source. 200w in a connection between two 4ga wires would certainly make smelly smoke eventually, but 200w in a connection on a large bus bar bolted to a wall panel with multiple 4/0 wires connecting off of it might distribute the heat quickly enough to avoid getting stinky, etc. That 200w, if left unnoticed because it never caused discoloration or fire, would be a 200w 'leak' in the system whenever it was operating at 100a. I used 100a as an example but unless you have a very large system it's rare to flow 100a anywhere except in very brief moments, but the system needs to not melt/catch fire at ANY point in its operating envelope, no matter how little time it spends there.

So the good news is any old multimeter CAN determine resistance indirectly by measuring voltage drop and then doing ohm's law to work back to the ohms. If you can measure the current with a dc clamp on the meter, or simply by reading it off the inverter screen/app, and then measure the difference in voltage across the connection (i.e. from before to after), it's just amps X voltage drop = ohms in that connection.

Or just touch it with your hand (<60v dc parts only) when the system is loaded down and see if it's warm. If it's not warm it may not be perfect but it also isn't dangerous. At that point whether you need to know an exact number is up to your personality.

 

[JRH]

Ok …wow… I need to stew on that a bit… thank you for your time
and thoughts… im not sure what to do from here except do what I always did on my boat for years and run it awhile and feel stuff to see if its too warm…
There seems to be many rabbit holes in this hobby-craft…and deep ones…
my head spins at times…
starting tomorrow I’m going to stream everything to the cloud from my I- phone ,so if I blow up the house and yard and propane tank and then the whole block, it will make great video for the survivors to talk about…
hopefully there will be more questions from my corner… ?

seriously thank you…Jim..

 

[koobs]

Seems like you're putting way too much thought into this than necessary.
If you've got a good hydraulic crimper and have cut a few crimps apart and your technique is good, I wouldn't worry further.
Hook it all up and stress test the system to the max amps it will transfer and even higher if you can simulate fault conditions. Check all connections during testing, ideally with a thermal camera if you can.
Pass the stress test then no need to worry further.
For example I just finished crimping a series of 35mm2 connections for a camping battery. Stress tested the system to 200amps continuous for about 10mins to assess for warm connections. No issues, so put system into service. Done.