wire question

Ruen

Hi guys,
I'm building an off-grid solar system.12 V DC .My question is about the type of the wire between the batteries and the load- solid or stranded?

BB.

Re: wire question

Really does not matter for DC.

For AC loads (like an inverter), if your wire gauge is larger than 0000 (4 ought), then you should use stranded.

In reality, you will probably be using stranded anyway as solid wire is very difficult to bend and move around when connecting.

I would only use very fine stranded cable (like welding cable) if you need really flexible wire and/or there is a lot of vibration or movement in the wiring. Fine wire is less susceptible to work hardening vs thicker strands/solid copper cable.

Very find welding cable stranded cables are usually more difficult to properly terminate. Crimp connections and wire binding posts tend not to hold well on fine strand cable.

If you are interested, read about the Skin Effect for AC circuits.

-Bill

RCinFLA

Re: wire question

The best welding cable is Excelene. It has heat resistance insulation that is great for soldering on connector.

Welding cables and soldered on connector are not UL approved. NEC recommendations generally require idiot resistant methods and since soldering requires some amount of skill it is not approved for attaching connectors.

I have a crimper but prefer soldering on connectors.

BB.

Re: wire question

NEC is written to ensure that mechanical connections remain if there is overheating/other failures.

Solder is a high resistance (relative to copper) material and will focus energy of high currents at the solder joint--In extreme situations (like lightning strike), even blowing the solder right out of the joints.

There are other secondary issues with soldering and stranded cable--the end of the solder joint provides a fulcrum for bending--causing the cable to fail from flexing much sooner than a pure "properly designed and made crimp joint"...

I also have a bit of an issue with corrosion from solder/flux (even rosin core) wicking up the cable strands--but I grew up on the coast and salt air would get into everything, causing electrical problems).

In the end, if you solder a connection (and we all do at times)--Have the cable fully supported (no bending at the solder joint) and ensure that the cable does not cause more problems in the solder melts and the cable were to slip out of the connector (and possibly short to a bus bar / battery terminal).

-Bill

Ruen

Re: wire question

Thanks for the reply!