Okay, let's break down the wiring requirements for Enphase IQ Battery 5P systems and why you CANNOT reduce wire size in a daisy-chain fashion like #4 -> #6 -> #8 -> #10.

Understanding the Fundamental Principle: Ampacity and Overcurrent Protection

The core principle of electrical wiring is that the conductors (wires) must have sufficient ampacity to safely carry the expected current, and that the circuit must be protected by an overcurrent device (like a circuit breaker) that will trip before the wire's ampacity is exceeded.

Why you CANNOT Reduce Wire Size Like That



Overcurrent Protection

The 80A breaker is designed to protect the entire circuit from overcurrents. If you reduce the wire size along the circuit, the smaller wires will be the weakest link. The 80A breaker is sized for the #4 wire and will not trip until 80 amps is flowing, which is likely more current than the #6, #8, and #10 wire can safely handle. This creates a significant fire hazard.

Current Distribution

Even if the total current never exceeds the ampacity of the smallest wire, there's no guarantee that the current will distribute evenly across all the batteries and wire segments. Small variations in resistance can cause one segment to carry more current than intended, potentially overloading it.

Code Compliance

The National Electrical Code (NEC) and local codes require that conductors are sized according to the load they are expected to carry and that they are protected by an overcurrent device sized appropriately for the conductor's ampacity. What you are suggesting violates those codes.

Enphase Requirements

Enphase installation manuals will explicitly specify the wire size required for their battery systems. You must follow their instructions for safe and compliant installation.

What the Enphase Installation Manual Says (Generally)

The Enphase IQ Battery 5P Installation Manual requires a dedicated conductor for each battery from the overcurrent protection device (OCPD). It also requires wire sizes to be consistent, so all wires running to all batteries need to be the same size.

The Correct Way to Wire the Batteries

With an 80A breaker and 4 batteries, the general guidance is as follows:1.

Dedicated Runs

Run a separate wire from the 80A breaker to each of the four batteries. This is called a "home run" or a "star" configuration.2.

Wire Size

Size each of these wires based on the maximum current the battery can draw. The Enphase IQ Battery 5P has a maximum continuous output current of 25A. Considering derating requirements for temperature and conduit fill, and voltage drop, #4 AWG Copper is usually selected.3.

Terminate properly

Ensure all connections are made using properly rated connectors and torqued to the manufacturer's specifications.

Important Considerations



Enphase Documentation is Key

Always consult the official Enphase IQ Battery 5P Installation Manual for the specific wiring diagrams, allowed wire types, conductor sizes, overcurrent protection requirements, grounding requirements, and any other specific instructions for your region and application.

In Summary:

You must run separate wires from the breaker to each battery, and you must use the correct wire size based on the breaker size and the current rating of the battery, following all Enphase requirements. Do not* reduce the wire size in a series or daisy-chain arrangement. That is a dangerous and code-violating practice. Flag for review