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To crimp or solder.....


16bitSprite

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Seems that there is many different opinions online about this topic. To some degree it has been covered in recent posts. With the recent connection failures in the gotway models, it seems like it may need a bit more in depth discussion. Feel free to add to this below because I am in no way an expert and the following is only my opinion after some basic googling. 

Originaly after reading about the failures I addressed the problem straight away with what I have been used to. Soldering has always been a hobby of mine so I was fairly confident in my abilities. I decided to bypass a connector all together as it's just one more  place a failure can occur. After doing more research both here and online, I got a little concerned that a lot of people shy away from solder as it is prone to failure from cold solder joints. From what I understand age, temperature change and high power levels can be a contributor to this. Not wanting to be a test dummy, I opted to change my original fix and have gone with crimps (butt joined, no connectors).I read that they can be more effective than solder if done properly as the crimp will create a gas tight weld. After pulling very firmly on the wires, I concluded that the crimps were a good strong solution. I don't think they will be giving out any time soon. So far I have just under 100km with no failures. 

What I found a little concerning is that some people recommend against soldering and crimping the same join claiming that the rigidity of a crimp can be compromised by the solder. This is precisely what gotway are doing with new wheels. Is this right? Is there cause for concern with this new fix? What is your recommendation for the strongest connection and why? Crimps, solder or both? 

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I say crimp is fine and will hold if properly done. 

If you want an extra comfort and security use solder as well.

To crimp a solderd connection and then soldering again is bad in my opinion.

Whe crimping you press agains the material (copper and solder) if you then melt that solder the pressure of the crimp is decreased when you melt the solder so I bet if you heat that connection again with a soldering iron you can pull the wire out of that crimp.

If you must solder and crimp then you should crimp against the pure copper of that cable then solder to secure.

My 2 cents.

 

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5 hours ago, Xima Lhotz said:

I say crimp is fine and will hold if properly done. 

If you want an extra comfort and security use solder as well.

To crimp a solderd connection and then soldering again is bad in my opinion.

Whe crimping you press agains the material (copper and solder) if you then melt that solder the pressure of the crimp is decreased when you melt the solder so I bet if you heat that connection again with a soldering iron you can pull the wire out of that crimp.

If you must solder and crimp then you should crimp against the pure copper of that cable then solder to secure.

My 2 cents.

This is my opinion also, if crimping, do it before soldering (don't even pre-tin the wires). The crimp should hold the wire in place alone, adding solder should lower the resistance at the crimp. Proper crimping tool helps with getting the crimps done better, but they're usually connector-specific, and depending on connectors, can cost a pretty penny, getting something like $100+ crimping pliers for specific connectors to do just a few connectors is probably not worth it... Just looking at TME's crimping tool options, the price range is from about 10€ to over 1000€ for the tool alone  :o

Downside of crimping seems to be that the crimp-connection usually has (at least slightly) higher resistance than soldered connection (and if done badly, very much higher, not to mention that it can become loose), downside of soldering is the risk of cold solder joint and/or the wire moving while the solder cools down, in which case there might be (non-visible) micro-fractures in the joint which might cause it to break over time and the connection isn't as good. Also with large connectors requiring lots of heating the wire can "wick" solder inside the sheath for some length, which will make it rigid.

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I was told by the installers of my two electric car charging points, two seperate firms six months apart, that soldered joints are not acceptable for any high power electrical connection as the temperature can rise high enough to soften the solder and that is why crimped joints are specified by all the regulations.

This also applies to the ferrules they crimp onto the flexible braided charging cables before inserting them into the clamping screws.

 

 

 

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  • 4 weeks later...

Also Crimping is not trivial. If you crimp too hard, you basically just cut the wire and it will fail. 

Crimp should be done with the exact force described by the connector manufacturer so you make good contact and also so you do not break the wire.

If you do not have the special tool, I would recommend do some test crimps by hand and pull very hard to see if you can pull the cable out. Also do a test crimp were you do it very hard and see how badly the cable is cut during crimping.

Then once you understand you can take the risk and crimp by hand.

 I agree that pre-soldered wires should not be used on high watt applications.

Use clean wires and crimp properly.

I believe adding solder after crimp helps contact resistance and I think it should not affect the crimp but I have to do some digging and see if I find some papers on that.

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2 hours ago, OliverH said:

Crimping is a wide definition. Real crimping where the teeth go inside the wiring is good.

 

2 hours ago, Carlos E Rodriguez said:

Also Crimping is not trivial. If you crimp too hard, you basically just cut the wire and it will fail. 

Crimp should be done with the exact force described by the connector manufacturer so you make good contact and also so you do not break the wire.

If you do not have the special tool, I would recommend do some test crimps by hand and pull very hard to see if you can pull the cable out. Also do a test crimp were you do it very hard and see how badly the cable is cut during crimping.

Then once you understand you can take the risk and crimp by hand.

 I agree that pre-soldered wires should not be used on high watt applications.

Use clean wires and crimp properly.

I believe adding solder after crimp helps contact resistance and I think it should not affect the crimp but I have to do some digging and see if I find some papers on that.

To be more specific, a "good" crimp done with proper tools is more often called "cold soldered" or "cold weld" (don't know if that's the correct term in English, but that's what it's called in Finnish). Here's one picture that Google image search for that brings up:

TEST%20CRIMP%2010-12%2006MAR15_zps2jo3zi

Unlike "cold [solder] joint", a "cold weld" is a good thing. Look at the last picture in the image above; in "cold weld", the conductors within the wire have become pretty much solid mass pressed against the connector (inner) surface: that's more or less a "perfect joint". But, this kind of joints are mostly possible only with the proper tools, and as I stated above, the tools can be connector-specific and fairly costly (but not always), so getting such for a few connectors may not be (financially) worth it (ie. how much sense it makes to buy a, say, $500 tool + connectors to make a three connectors for motor phases for your own personal use? ;)). Of course, I'd prefer that the manufacturers use such tools and connectors in the first place, for mass production it should not be that big of an investment to get a bunch of tools and good connectors for each wheel for the production line to make sure the connections are good... The pneumatic hammer seen in some Gotway video (or was it Kingsong? Anyway, about their new connector procedure...) probably does the job, ie. compress the single conductors in the wire into a (more or less) solid mass?

Basically, in this context, a "cold weld" seems to mean that the conductors "weld" together without actual welding (heating).

For a proper "cold weld", soldering (or trying to, heating that lump of metal may not be easy ;)) it afterwards won't probably do much (ie. neither make it better or worse), the connection's pretty much solid all the way already :P

 

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I've studied electronics design for extreme conditions for use in satellites and have certificates for soldering highpressure pipes. Soldering with fluss ensures oxygen is kept out of the bond. I would solder with generous amounts of fluss to consolidate the joint and prevent corrosion. I've taken apart my wheel and repaired it so many times (harsh roadconditions) that I know you can't just melt rubbersement over the boards and wires... What you need is heavy duty insulation on the wires that go between the battery, the control board, the motorwindinds and the charging circuit. Those wires can be clamped down with high-quality strips or metal clamps and reinforced sparsely with rubbercement where needed. The rest of the electronics and wires will corrode over time or short out from the inevitable failure of any moistureseal. You can prevent this by affixing cooling ducts to components that produce heat and covering all but the cooling ducts in wax. Carefully wax with future maintenance in mind. If done with care and maintained this leaves your EUC able to ride in any weather and any temperature. Maybe a better option for the wax (but still with re-inforced main leads) is to take your system completely apart at least once a week for a thorough cleaning of especially the wires and circuitboards and replacing anything that is measured to be outside the specified tolerance for that specific component

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Done some repairs on electrical systems on heavy trailers aswell. Industry standard was to solder. Both on repairs and in assembly. School standard was to crimp, but the wise and experienced in the trade said "Crimp if you want to repair it after a while. Do a bad job and you'll hear it. Solder if you want to know your work won't cause a failure. It's nice to have the returning client greet you with a smile. The client knows if you crimped.".
Crimping works in a school setting where you set the components on a bench and they stay there. In this setting there is alot of vibration, moisture, dirt, fluctutating temperature etc. The connection needs to be consolidated properly so no gunk gets into the wire or the joint. Crimping creates a weak link, allows movement beyond the joint, dirt and oxygen into the wire if you make the tiniest of errors. Soldered joints are quick and easy to make strong joints that last as long as the insulation on the wires can withstand crackling

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6 hours ago, Cryptonitor said:

I've studied electronics design for extreme conditions for use in satellites and have certificates for soldering highpressure pipes. Soldering with fluss ensures oxygen is kept out of the bond. I would solder with generous amounts of fluss to consolidate the joint and prevent corrosion. 

Fluss = flux?

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19 hours ago, Cryptonitor said:

I've taken apart my wheel and repaired it so many times (harsh roadconditions) that I know you can't just ...  

heavyduty insulation on the wires that go between the battery, the control board, the motor and the charging circuit ...

You can prevent this by affixing cooling ducts to components that produce heat and covering all but the cooling ducts in wax.

Pictures? I like what you are thinking and curious if you've ever taken pictures when you did the cleaning.  

 

Also I think fluss must be flux; otherwise I don't know what that is haha.

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22 hours ago, Cryptonitor said:

Done some repairs on electrical systems on heavy trailers aswell. Industry standard was to solder. Both on repairs and in assembly. School standard was to crimp, but the wise and experienced in the trade said "Crimp if you want to repair it after a while. Do a bad job and you'll hear it. Solder if you want to know your work won't cause a failure. It's nice to have the returning client greet you with a smile. The client knows if you crimped.".
Crimping works in a school setting where you set the components on a bench and they stay there. In this setting there is alot of vibration, moisture, dirt, fluctutating temperature etc. The connection needs to be consolidated properly so no gunk gets into the wire or the joint. Crimping creates a weak link, allows movement beyond the joint, dirt and oxygen into the wire if you make the tiniest of errors. Soldered joints are quick and easy to make strong joints that last as long as the insulation on the wires can withstand crackling

I think you are totally wrong. If solder wicks up a wire that is exposed to vibrations it will eventually fracture at the point the wicked solder stops. Meaning you have a stiff wire and a frlexible wire strand at which junction it will focus all the flexión and eventually fracture. On a proper crimp the wire supported at the wire insulation because the wire insulation is also crimped by a separate collar that bites on the wire insulation. This protects the wire from flexing at the crimp and the wire retains is flexibility through the entire wire length with no stiff point that would develop a fracture. 

That being said when it fractures is a matter of how long and how strong the vibrations are. But given the two methods, the wire that has wiked solder up under the insulation will fail before the crimp only wire. 

If it has not failed in your experience is because there is not enough vibration and time to develop it but it will happen eventually. 

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