Practical Sailor · video

What this video covers

Connecting a lithium house battery bank directly to a boat's alternator risks catastrophic electrical failure due to two primary issues: sudden BMS-triggered shutdowns and alternator overheating. Lithium batteries feature a Battery Management System (BMS) that acts as a panic switch, disconnecting the battery if it detects overcharging or low voltage.2:09 If this occurs while the engine is running, the sudden loss of load causes the alternator's voltage to spike, potentially exceeding 100 volts DC and destroying sensitive electronics or the alternator's internal diodes.2:34 Furthermore, lithium batteries accept high-amperage charging currents until full, forcing the alternator to operate at maximum output for extended periods.3:44 Because alternators rely on internal fans driven by engine RPM for cooling, low-RPM cruising often leads to overheating and failure.3:55 To mitigate these risks, maintain a lead-acid start battery connected directly to the engine to provide a stable load and install a DC-to-DC charger to manage the charging profile for the lithium bank.5:03

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