bundling cables together that carry current in different directions

So I’m bundling together a dozen or so wires to hook up the front end accessories…

I’ve got headlights, indicators, rad fan, fan switch, horn and alternator… (+ve, charging light, and ign live)

I’ve currently gone with a fairly loose concentric twist for neatness, using the alternator cable as a “core”, and have wrapped all the other cables around it, and covered with heat shrink, but I’m concerned that this isn’t best practice…

As the current coming from the alternator will be travelling in the opposite direction to the current in all the other cables, should the alternator cable be wrapped separate to the other cables, rather than how I’ve done it?

Is this nothing to worry about, or should I unwrap it all, separate the alternator cable, twist all the remaining cables together, heat shrink them both separately, then use cable ties to tie both sections together for neatness… or will having them separately bundled and heat shrinked be enough, and then I can add another layer of heat shrink over both of them?

I’m not sure what problem I’m looking to overcome, as I’m unsure on the science behind it, but I guess I’m looking to avoid some sort of interference, or maybe some unintentional heat build up???

If I’ve got 60amps coming from the alternator heading in one direction, and say 20amps going to the rad fan in the other direction, while they’re twisted together, will this cause any problems???

All the cables are correctly sized for their use accounting for voltage drop over their length etc etc

Look forward to hearing your options!

Many thanks!

Pierce

I put power and ground together in a cable all the time. By definition, the current is flowing the opposite direction. I would not worry about what you have described. Neither the Fan or the Alternator will be affected.

Steady state, or near steady state currents are fine, especially when there aren't signal/data carrying wires near them..

The problem is when there are changes in the currents with sensor wires close to them. Sudden changes in current causes the magnetic fields around them to change suddenly, and that change in magnetic field induces a voltage in nearby wires. Those will usually have negligible affect, but some sensors use milli-volt, or milli-amp variations for sending their data to the ECU, and the induced voltages can throw them off.

That’s great news, thank you David and Gord for taking the time to help.

When it comes to the ecu wiring, I’ll be sure to keep things like the crank sensor etc shielded and separate, for reasons I now understand.

Much appreciated.

Pierce