crimp vs solder in miliohm

[conquistador]

Today I ran a test crimp vs solder.
I used 4mm² copper which translates to 10AWG and cheap brass lugs. The cheap crimping tool is from Aliexpress.

To measure the resistance, I feed 1A through the wire via a bench power supply, limited at 1A. Then I measure in the 200mV setting on the Multimeter. This translates to 1mV= 1miliohm, so basically the Voltmeter shows in miliohm in the 200mV setting.
Here are the results:

crimped only in the 4-6mm² slot of the tool:
1.0 and 0.8 mOhm

crimped in the 4-6mm² slot and then in the 2.5mm² slot
1.7 and 3 mOhm !!

These ones i re-crimped in the 4-6mm² slot and got
0.7 and 0.8 mOhm after recrimp

After measuring, I soldered all of them with a 100W iron and 40/60 tin, rosin flux:

the recrimped: 0.5 and 0.6 mOhm
the crimped in the 4-6mm² slot and soldered: 0.5 and 0.5 mOhm

While I acknowledge that my tool and my lugs are crap, soldering after crimping seems to improve resistance significantly.

 

[kpw]

interesting, I would love to see this experiment done with larger wire size like 2/0

 

[HRTKD]

Is it possible that the solder covered for a bad crimp? I don't know, just throwing that out.

 

[John Frum]

I used 4mm² copper which translates to 10AWG and cheap brass lugs.

4 millimeters squared is roughly equivalent to 12 awg.
Brass is not nearly as good a conductor as copper.

Electrical Conductivity of Materials - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

https://muellergroup.net/wp-content/uploads/2016/04/MM2-AWG-Conversions.pdf

 

[brb58]

If you actually did a proper crimp, no solder would penetrate the crimp since it does a cold weld of the joint. Basically, your test proves that you need to buy a better crimping tool.

 

[conquistador]

If you actually did a proper crimp, no solder would penetrate the crimp since it does a cold weld of the joint. Basically, your test proves that you need to buy a better crimping tool.

Is it possible that the solder covered for a bad crimp? I don't know, just throwing that out.

Even if I love my Aliexpress crimping tools, I have to agree with you guys here. Per definition, the crimping is something like wire wrap in the old days, which should leave a gas tight connection. Apparently it is not in my case.
Are there any good crimping tools out there for small lugs like the ones in the pictures?

 

[efficientPV]

You didn't show how that test was made. There can be a lot of error even in a four wire connection. I have one of these, a HYPATIA 309 which can test and automatically calculate the ohms at any current. At over 100A max it will melt alligator clips.

 

[brb58]

Even if I love my Aliexpress crimping tools, I have to agree with you guys here. Per definition, the crimping is something like wire wrap in the old days, which should leave a gas tight connection. Apparently it is not in my case.
Are there any good crimping tools out there for small lugs like the ones in the pictures?

I bought mine trough Rod Collins on the Marine How To site. Unfortuantely Rod had a stroke so his store is down. For 22AWG through 10AWG, they are the best crimpers out there and that's saying something since I am an EE in a production environment.

This is what they looked like:

Purchase a Pro-HST - Heat Shrink Crimp Tool by Compass Marine How To

pbase.com

They also aren't cheap...around $140

This is them also but for much more:

Heat Shrink, Solder Sleeve Ratchet Crimp Tool - 24-10 Gauge

This ratchet crimp tool is specifically designed for crimping 24-10 gauge heat shrink, nylon and vinyl insulated terminals. The ratchet release prevents insulation damage on your terminals.

www.delcity.net

Rod's how to site is still up. This is the best I have ever seen about crimping.

Marine Wire Termination - Marine How To

Marine Wire Termination - Tools of the Trade MHT Recommended Tools: The products below are our top picks for crimp tools. RecommendationsI include; PRO GRADE, MARINE GRADE, & PENNY SAVER GRADE. Every tool recommended BELOW, we have tested here.

marinehowto.com

 

[toms]

I use these for small terminals.

Iwiss 3220M