by raysun on Mon Feb 11, 2019 10:34 am
Like a lot of practical electrical engineering on critical limits, the answer has a large component of "it depends".
I assume the guidance in the documentation is to minimize the effect of induced voltage (EMF) and companion induced currents. When current flows through a wire, a magnetic field is created. When the current stops flowing, the magnetic field collapses, creating an EMF (voltage) across the conductor with resulting current flow. How much EMF and current is induced is a function of the strength of the magnetic field and how fast it collapses.
A case might be solar harvest on a day when the sun is high in the sky, and fast moving heavy clouds pass in front of it. The charge controller is feeding high current to the battery in full sun, a sudden change in solar energy caused by a passing cloud would cause a sudden change in current flowing to the battery. The sudden collapse of the magnetic field will induce an EMF and current. A great enough rate of change can induce enough EMF to cause damage in some extreme cases.
A more extreme case might be the charge controller(s) producing high current and then the battery disconnect breaker is opened. This could create enough EMF to arc across the breaker contacts and burn them.
The guidance with keeping the + and - conductors tightly bound is an attempt to limit the induced EMF and current by having the two collapsing magnetic fields cancel each other's inductive effects to the extent possible.
Is your system going to burn to the ground if the conductors don't pass through the same knockout? Not likely unless you are running a good number of panels and controllers.
Will the minor "insults" of induced EMF shorten the service life of the equipment? Perhaps, or perhaps not, but it's safe to say it will not improve the service life.
Personally, it would have been more convenient to ignore this guidance when routing the cables, but yielded to "better safe than sorry" and rerouted them.
Ya pays yer money and takes yer chances.