# Reasons for using separate sets of wires for the solar controller and the loads to the battery vs using a bus-type configuration

This has been discussed a few times, both here and on other sites, but the justifications given are usually very light. Here are a few examples that say that you should run separate sets of wires to the battery for the charge controller and the loads:

The question is basically about these two configurations:

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

The reasons given are:

1. Any extra voltage drop (due to connectors, etc) on the battery side of the charge controller can confuse it, resulting in undercharged batteries.
2. Additional noise introduced by the charge controller into the voltage seen by the load that would otherwise be remedied by the battery impedance.

Are there any other practical considerations against doing it one way or another?

EDIT: To add a little more detail on why you wouldn't just always go with separate sets of wires, suppose that the battery compartment is only accessible via an 8 feet pipe that's 1 inch in diameter (my exact situation right now). That means you can either run four 4 AWG wires through it or two 2 AWG wires. When the charger and the load are pushing/pulling 30 amps (not at the same time) to/from the battery, the wiring drops 0.12V with the 4 AWG wire, while it only drops 0.075V in the 2 AWG case. When the charger is powering the load directly, the current doesn't have to travel the length at all and there's no drop.

• Those arguments seem a pretty good reason to use a wiring scheme as shown in your first picture. Aug 22, 2017 at 9:59
• All else being equal, I agree with you, but please see my edit. Aug 22, 2017 at 17:24
• Can your charge controller do remote voltage sense? Aug 22, 2017 at 22:31
• @ThreePhaseEel I wish it did, but no - it can't. Aug 22, 2017 at 23:42