soldering a battery lead

[mikegold]

soldering

As you should be aware it is not correct to use solid wire aboard due to the posibility of stress fractures, I.E. case hardening due to vibration so why create solid wire connections by soldering?. Crimps done correctly are perfectly acceptable,where as the link wire is purchasable in any motor supplier

 

[Ardenfour]

any number of these links, in all sizes at car scrappies for pennies...

 

[elton]

Is there a qualified metallurgist in the house?

Please can you tell us the answer, to solder or to crimp multi-stranded copper cable to battery terminals, so we can put a rest to all this dogma?

 

[NorthUp]

We haven't touched on modern lead free solder yet, there's a long way to go here.
I crimp, personally, no hot work permit required!

 

[cozzykim]

Nobody has mentioned this so far.

It looks to me like the original joint has failed due to overheating?

The remains of the original solder, which can be seen through the opening in the lug, are bright and not dull as a dry joint would be.

The thread of the bolt where it comes out of the nut is also black, this is where the heat has come from, the resistance in that loose or dirty bolt/battery clamp joint has melted the joint to the lug. (I see this all the time at work, not battery connections admittedly)

I would make a new cable, probably with whichever parts and methods are most readily available, making sure that there is a loop of cable to absorb mechanical stress/vibration.

I don't think there is much to choose between soldering and crimping in this application.
I use both methods for connecting lugs to wires/cables ranging from "16s" to parallelled 120sqmm welding cables carrying 1000s of (H.F.) amps. For high power connections I would prefer crimps as they retain the conductor flexibility and the insulation can be cut right next to the crimp without damage to the cable covering caused by soldering.

For reliability, (and low resistance) absolute cleanliness is necessary whether it be solder or crimps.

In this case absolute cleanliness and correct tightness of the bolt connecting the lug and battery clamp would have prevented the failure.

If you go the crimp route use the correct size/type of crimp lug for the cable and the correct crimp tool.

If you solder use the correct size/type of lug for the cable, a gas torch and a heat sink to protect the cable as previously described.
Get rid of any flux residue afterwards as it will eventually cause corrosion.

Kim

 

[JohnTH]

But once the copper wire and the battery lug have been heated for soldering both have been annealed !

If it were me, I would just clean it all up and solder it all back together.

73s de
Johnth

 

[sarabande]

Cozzykim and everyone - I think that the separation of the cable from the clamp is probably due to my practice of undoing the nuts and removing the unit from the battery terminal each time I leave the boat (I can never tell how long before I'm down for a sail again).

The batteries are underneath a floor member and I have to move them a bit to reach the nut. This means that I have been placing a strain on the cable and 'wiggling ' it a bit each time I undo or do it up.

Looking closely at the clamp, it seems that there is no evidence of solder on the metal on the inside of the clamp; there's a lot of dark flux, through. The cable does have solder in between all the strands, and seems 'solid'. It therefore seems that the cable was placed in the clamp, squeezed quite tight, and then heated and soldered, but not properly (perhaps not heated long enough to bring the clamp up to solder melting temp ?).

I'm pretty convinced that my movement of the two batteries and the connecting cable has placed a (?rotational) strain on the soldered joint causing the cable to separate from the clamp.

My view after all these posts from so many people, (isn't the forum wonderful !) is that since I am not a skilled solderer, I'll get the local car electrical people to make up a short length of cable to new terminal units, and crimp the endings. I'll also leave the + to - connection in place between the two batteries when I leave the boat, and just disconnect the 24v + and 24 - terminals.

I'll get the camera back at lunch time and take some close-ups.

Many thanks to all.

 

[cozzykim]

But once the copper wire and the battery lug have been heated for soldering both have been annealed !

If it were me, I would just clean it all up and solder it all back together.

73s de
Johnth

Except that soft solder melts around 230 - 250C and copper requires around 700C to anneal.


@Sarabande
The inherent weakness in the original link is in the number of unnecessary joints, how about something like these screw type clamps? As long as you use the max size recommended cable for a snug fit, and keep them tight, they would be fine IMHO

Kim

 

[lenseman]

. . . . . a one-time electronics technician qualified to work on RN battleships . . .

That must have been a VERY, VERY long time ago!!

Even when I was in The Andrew, they had been long gone.

 

[elton]

That must have been a VERY, VERY long time ago!!

Even when I was in The Andrew, they had been long gone.

What had been long gone?

 

[lenseman]

What had been long gone?

I can see that Senility DOT com loaded high in your upper memory this morning!

I was talking about Battleships. They had been long gone!

 

[lenseman]

. . . . and whilst I am on this thread, if you are going to use open flame soldering near a vented battery, especially in a confined space below . . . . . !!

Be aware of the hydrogen gasses given off by the batteries which might cause you problems!

 

[cozzykim]

. . . . and whilst I am on this thread, if you are going to use open flame soldering near a vented battery, especially in a confined space below . . . . . !!

Be aware of the hydrogen gasses given off by the batteries which might cause you problems!

Top advice.

Do I also see a flash mark on the unsoldered clamp, from a spanner maybe?

Not a good idea to have uninsulated tools around a big battery, I once had to duck when some berk decided to test for charge in a traction battery by putting a spanner across the terminals, some of the pieces (and acid) ended up 20 yards away!!

 

[elton]

I can see that Senility DOT com loaded high in your upper memory this morning!

I was talking about Battleships. They had been long gone!

Are you drunk?