The Complete 2026 Boating Guide: New Codes and Standards

Two significant code changes took effect for the 2026 boating season — one from the National Electrical Code covering marina shore power, and one from ABYC covering lithium battery installations onboard. Wesley walks through both in the video above. Here's the breakdown.

Update 1: NEC 555.35 — Marina Ground Fault Protection

What changed: NEC Section 555.35 went into effect January 1, 2026. It requires marinas to install highly sensitive ground fault protection on dock electrical systems, designed to detect and interrupt stray electrical leakage before it enters the water.

Why it exists: Electric Shock Drowning (ESD) is caused by AC current leaking into marina water. When a swimmer enters energized water, current can pass through their body between the source and a ground point. NEC 555.35 mandates the dock-side equipment that catches this leakage before it becomes dangerous.

The unintended consequence: The new dock systems are highly sensitive by design. Minor ground faults on vessels that older systems ignored now trip the shore power breaker repeatedly. If your boat is suddenly tripping shore power breakers and it never did before, the marina may have upgraded to NEC 555.35-compliant equipment and your boat has a minor fault that's now being detected.

The best solution: An onboard isolation transformer fully isolates your boat's AC system from the dock's grounding system. This eliminates the ground fault current path that triggers the marina's sensors, stops nuisance trips, and provides the most thorough protection against ESD on both sides — without requiring an expensive electrical inspection to track down every minor fault.

Update 2: ABYC Supplement 65 — Lithium Battery Installation Standards

ABYC issued Supplement 65 in 2026, updating standards E-11 (AC and DC electrical systems) and E-13 (lithium-ion battery installations). The E-13 revisions are the most consequential for anyone installing or upgrading a lithium battery bank.

System Design and Redundancy (Standard 13.6)

BMS is now mandatory. Every onboard lithium battery bank must have a Battery Management System that automatically disconnects under hazardous conditions — overvoltage, undervoltage, overtemperature, overcurrent.

Plan for critical loads when the BMS trips. Supplement 65 heavily recommends a redundant auxiliary power path for safety-critical systems: navigation lights, bilge pumps, VHF radio. If your main bank's BMS disconnects due to a fault, these systems should not instantly go dark. A small backup battery wired independently to critical loads accomplishes this.

Environmental protections now specified: Operating temperature bounds for the installation location; mechanical shock and vibration mitigation; water ingress prevention; terminal corrosion defense with tinned connections and proper enclosures.

Overcurrent Protection and Class T Fuses (Standard 13.6.6)

Every wire in a lithium battery system must have dedicated overcurrent protection. More significantly, Class T fuses are now a foundational requirement for main lithium battery overcurrent protection. Lithium batteries can deliver extremely high short-circuit current far beyond what standard ANL fuses or circuit breakers can safely interrupt. Class T fuses have a much higher Ampere Interrupting Capacity (AIC) rated for the fault currents lithium banks can produce.

If a bank's potential short-circuit current exceeds the AIC rating of the overcurrent device, the bank must be subdivided into smaller units to keep each segment's fault current within rating.

Manual Battery Isolation Switches (Standard 13.6.7)

Each separate battery bank must have a dedicated manual battery isolation switch — physical, independent of any BMS disconnect or solid-state relay. Requirements: manually operable (not electronically controlled); installed as close to the battery terminals as practical; readily accessible to the operator; and cannot be substituted by the BMS disconnect.

The logic: in an emergency, crew must be able to physically disconnect the battery bank without depending on the BMS to be functional. Electronic systems fail. The manual switch must work regardless.

Multi-Battery Banks and Chemistry Rules (Standard 13.6.8)

Mixing chemistries in series is prohibited. Lithium and lead-acid (AGM, flooded, gel) batteries cannot be wired together in series. Their voltage profiles, charge requirements, and failure modes are incompatible.

Balance before connecting in parallel. Any voltage deviation specified by the manufacturer must be normalized across all units before connecting. Bring batteries to the same state of charge before paralleling.

What This Means If You're Installing or Upgrading

A compliant 2026 lithium installation requires: a BMS on every lithium bank; Class T fuses as primary overcurrent protection; a manual isolation switch for each bank independent of the BMS; a plan for critical loads if the BMS disconnects; environmental protection for the battery compartment; and no mixed chemistries in series.

If you're connecting to marina shore power and experiencing breaker trips, an isolation transformer is the clean fix.

Blue Marine's ABYC-certified team installs to these standards on every build. If you have questions about bringing an existing installation into compliance or want a system designed to meet Supplement 65 from the start, schedule a free consultation.

Related reading:
Stop Your Boat From Corroding: Victron Galvanic Isolator Explained
LiFePO4 vs AGM Marine Battery: Which Should You Buy?
How to Wire Lithium Batteries in Parallel (Safely)