Lithium Batteries
What Marine Surveyors Look for in Lithium Battery Installations
Lithium batteries have become the preferred power source for an increasing number of recreational vessels. Lighter, longer-lasting, and capable of deeper discharge cycles than their lead-acid counterparts, lithium iron phosphate (LiFePO4) systems now appear in everything from bass boats to bluewater cruisers. For marine surveyors, this shift brings a new layer of complexity—and ABYC E-13 is the standard that governs it.
What E-13 Actually Covers
ABYC E-13 is an installation and safety standard for lithium-ion battery systems aboard recreational vessels. It does not certify or approve individual battery products; rather, it establishes the requirements that installers, system designers, and boat owners must meet to reduce the risk of thermal events, electrical faults, and other hazards unique to lithium chemistries.
The standard addresses:
Cell and module construction — acceptable chemistries, enclosure materials, and measures to limit thermal propagation between cells
Battery Management System (BMS) requirements — mandatory protections for over-current, over-charge, over-discharge, temperature extremes, cell balancing, and fault reporting
Charging behavior — specified charge profiles, temperature-compensated charging, and compatibility with alternators, shore chargers, and solar controllers
Wiring and fusing — conductor sizing, fuse/breaker placement near the battery positive terminal, connector ratings, torque specs, and routing practices
Marking and documentation — durable labels, capacity and voltage markings, and comprehensive installation documentation (datasheets, wiring diagrams, BMS specifications, environmental limits)
The July 2025 Revision: Key Changes
Version 2 of E-13, effective July 2025, introduced several clarifications that directly affect how surveyors evaluate lithium installations:
1. Remote Switch Requirements (E-13.6.7.1.1)
The revised standard explicitly requires that a remote switch directly interrupt the energizing power for the battery contactor—not merely send a control signal to the BMS. This is a critical distinction.
What to look for:
If the remote switch only provides a low-voltage control signal to a BMS (for example, certain Victron Lynx configurations using pins 10/11), it may not meet the new requirement
Systems using bistable contactors rather than monostable, normally-open contactors can also fall short
Manual mechanical disconnects (such as the Blue Sea ML-RBS knob) remain compliant because they allow direct, fail-safe isolation independent of BMS logic
2. Fusing and AIC Requirements
E-13 guidance leans toward Class-T fuses for lithium installations due to their high Available Interrupting Capacity (AIC). The rule of thumb derived from E-11: 5,000 AIC per 100 Ah.
Battery Capacity
Required AIC
Typical Fuse Choice
100 Ah 5,000 AIC Class-T
300 Ah 15,000 AIC Class-T or certified high-AIC breaker
600 Ah 30,000 AIC Class-T
What to verify:
NRTL marks (cULus, cETLus, TÜV) and vendor traceability on breakers
Fuse placement per the 7-inch rule (distance from battery terminal)
Avoid reliance on MRBFs for primary lithium protection where AIC or failure modes are unclear
3. Parallel Battery Configurations
Connecting lithium banks in parallel with manual switches (1-2-Both or simple on/off at each battery) introduces balancing and fault risks. When batteries at different states of charge are suddenly paralleled, massive equalizing currents can occur.
Acceptable approaches include:
Dedicated BMS systems that orchestrate safe paralleling
Serial backup configurations with isolated AGM or starter banks charged via DC-DC converters
Clear isolation procedures for servicing
Survey Checklist for Lithium Installations
When evaluating a lithium battery system, consider documenting the following:
Documentation Review
Manufacturer datasheets specifying charge/discharge limits and temperature parameters
BMS specification sheet with documented protective behaviors
Wiring diagrams showing fuse placement, conductor sizing, and disconnect locations
Installation instructions from the battery manufacturer
Physical Inspection
Batteries securely restrained with minimal movement
Appropriate fusing (Class-T preferred) within 7 inches of positive terminal
Proper conductor sizing per ABYC A-31
Remote disconnect that directly interrupts contactor energizing circuit
Durable labels with capacity, voltage, and safety markings
Evidence of third-party testing certification (SAE, IEC, or UL)
System Verification
Audible or visual alarm capability for impending BMS shutdown
Compatible charging sources (alternator regulator settings, shore charger profiles)
Backup power source for critical electronics if primary bank fail
Common Deficiencies to Watch For
Based on field experience and the updated E-13 requirements, these issues appear frequently:
Remote switches that rely solely on BMS logic — The switch sends a signal, but the BMS decides whether to disconnect. This creates a single point of failure.
Undersized or improperly rated fuses — Many installers use what they have on hand rather than Class-T fuses with appropriate AIC ratings.
Missing or incomplete documentation — Without manufacturer specifications for BMS parameters and shutdown conditions, compliance cannot be verified.
Improper parallel switching — Manual 1-2-Both switches connecting lithium banks without balancing safeguards.
Uncertified components — Breakers and contactors lacking NRTL marks or marine environmental ratings.
Insurance and Compliance Implications
While ABYC standards are technically voluntary, they carry significant weight:
Many marine insurers reference ABYC standards when underwriting policies and evaluating claims
A lithium installation that does not meet E-13 requirements may complicate coverage or claims
Surveyors documenting non-compliant installations provide valuable information for underwriters assessing risk
When you identify deficiencies, clear documentation of what the standard requires versus what exists on the vessel helps owners, insurers, and yards understand the path to compliance.
Working with Manufacturers and Installers
E-13 compliance is a shared responsibility. Manufacturers must provide the technical documentation that enables compliant installations; installers must follow both E-13 requirements and manufacturer instructions; surveyors verify the result.
When evaluating unfamiliar systems, don't hesitate to request:
Written confirmation from the manufacturer regarding E-13 compliance of their recommended wiring configurations
Specific documentation of how the remote switch interrupts the contactor energizing circuit
Third-party test reports for AIC ratings on breakers
If a vendor cannot provide this information, that itself is a finding worth noting. abycinc.orgbattlebornbatteries.com
Staying Current
ABYC standards are reviewed annually, and lithium technology continues to evolve rapidly. E-13 will likely see further refinement as the industry gains more field experience with these systems.
ABYC membership provides 24/7 access to the current standards—essential for surveyors who need to reference the latest requirements when preparing reports. Professional development through ABYC certification courses and events like SUR/TECH also offer opportunities to deepen the understanding of electrical systems and earn continuing education credits.
The shift to lithium power represents a genuine improvement in marine electrical systems—when done correctly. E-13 provides the framework for safe installation, and surveyors play a critical role in verifying that framework is followed. Understanding the technical requirements, recognizing common deficiencies, and documenting findings clearly serves vessel owners, insurers, and the broader goal of keeping boaters safe on the water.