Alternator wiring

The alternator output is a rectified 3-phase AC signal. It has peaks and valleys. The battery is a low impedance storage device, that acts somewhat like a huge capacitor. The closer a electrical feed is to the battery, the more filtered and regulated it is. There are parasitic resistances in the system. The resistances result in voltage drops, so while nodes are connected by wires, the voltages will be different, and the differences increase with current flow. A scope may be used to view the voltages, and voltage drop and discover all this.

All this is important if you have electronic ignition, efi ....

Ignition manual for the Mallory Unilite says do not connect ignition suppy to alternator terminal is one example, the other is ECU feeds are supplied from a tap at battery terminal.