Cable selection

[Breakinit]

This is my first post in this forum, happy to join in. I have been living off grid since the 90's doing all installation myself. I'm beginning another upgrade from lead acid to Lifepo4 and adding a second array. I have been studying and trying to catch up on what is current. Reading in Victron's excellent pub. Wiring Unlimited I came upon this:

"When selecting cables avoid these mistakes: · • Don’t use cables with coarse strands. • Don’t use non-flexible cables. • Don’t use AC cables. "
There is no explanation that I could find for why this is so.

So since the beginning I have used coarse stranded, non-flexible cable that is intended for AC use for all my high current DC connections. I even have 4/0 standard cable from my local electric supplier connecting batteries to inverter, with lugs I made from copper tubing flattened drilled and soldered. It took some effort but doable and a lot less expensive. So my question is, why was/is this a mistake? Thanks for your time.

 

[sunshine_eggo]

soldered. It took some effort but doable and a lot less expensive. So my question is, why was/is this a mistake? Thanks for your time.

This is why you haven't experienced significant issues. If you crimp coarse strand wire into terminals, you don't get good contact.

Crimp-only with find strand wire is the preferred method. It's faster, and it's better for flexibility. Soldered connections can crack and are ultimately higher resistance than a high quality crimp. Quality crimped connections have near 100% copper to copper contact where soldering has a lot of the gap between strands filled with higher resistance lead and tin.

 

[timselectric]

Plot twist.

 

[Breakinit]

Great to know! Thanks. It has worked for 30 years. I wonder what the total lose from resistance in the soldered joints has amounted to over all these years. Current under the bridge.

 

[Partimewages]

Well that does twist things a bit.
However the problem is there are many poor connections no matter how they are made.

 

[Breakinit]

Plot twist.

Very interesting! Soldered connections just got boost. There seems to be some disagreement here?

 

[Partimewages]

JMO solder has its place but mobile connections if done properly probably should be crimp connections due to vibration.