BoatHowTo · video

What this video covers

Replacing lead-acid batteries with lithium-ion (LFP) cells does not inherently require larger battery cables, as the existing wiring remains sized for the boat's electrical loads.1:14 However, treating LFP batteries as simple "drop-in" replacements creates significant safety risks, primarily due to the potential for the battery management system (BMS) to disconnect abruptly.2:08 If an internal BMS disconnects while an alternator is charging, the resulting voltage spike can destroy alternator diodes or lead to thermal runaway and fire.2:49

Safe LFP installations require an external BMS that communicates with charging sources, such as a Victron voltage regulator, to throttle charging before a disconnect occurs.3:46 Furthermore, LFP banks produce massive short-circuit currents—potentially exceeding 20,000 amps—that standard fuses cannot interrupt.4:34 Installers must use fuses with high Ampere Interrupting Capacity (AIC) ratings, specifically Class T fuses in the U.S. or NH fuses in Europe.5:52 When paralleling multiple LFP batteries, each individual battery requires its own high-AIC fuse to prevent the combined short-circuit current from overwhelming the system.6:45

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