How Do I Charge a Lithium House Bank and a Lead Acid Starter Battery With My Alternator?
2 July 2023 · 7 min · 54K views
What this video covers
Lithium battery banks accept high charge rates until full, unlike lead-acid or AGM batteries that taper their intake as they reach capacity.0:48 This constant, high-amperage demand forces alternators to run at maximum output, generating significant heat that can lead to premature failure.1:56 To prevent overheating, boaters should install an external regulator to limit the alternator’s field voltage, effectively capping output at 50% to 70% of its rated capacity.2:41
In a system using a battery isolator to connect a lithium house bank and a lead-acid starter battery, the isolator provides a safety buffer.5:39 If the lithium battery’s Battery Management System (BMS) disconnects due to a full charge, the alternator remains connected to the starter battery, preventing a damaging voltage spike.5:39 However, battery isolators often cause a 0.7-volt drop and force the lithium bank to charge using a standard lead-acid profile.4:58 To verify charging, disconnect all other power sources, run the engine at 1200 to 1600 RPM, and monitor the house bank voltage for an increase.4:11
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