Boat Appliances and Lithium Battery Loads

An appliance affects a boat electrical system in two different ways: instantaneous current determines whether the inverter, BMS and cabling can support it, while operating time determines daily energy use. Both must be calculated.

Build a load record

Measure typical watts, startup or compressor surge, hours per day and whether the load runs through an inverter. For cycling equipment such as refrigeration, record real duty cycle in the expected ambient temperature. For discretionary loads, record when they can be scheduled during strong solar or engine operation.

Start with the daily power-use guide, then use the runtime calculator and inverter current calculator.

Continuous and cycling loads

Refrigeration, Starlink and navigation electronics can run for long periods. Small errors in watts or duty cycle compound across a day. Measure these loads before sizing around comfort appliances.

Short, high-power loads

Induction cooking, washing machines and some watermakers may use manageable daily energy but demand high current while operating. Check simultaneous loads and DC voltage drop, not only appliance wattage.

Air conditioning and reserve

Marine air conditioning can dominate both peak power and overnight energy. Model compressor cycling in the real cabin and climate. Preserve an essential-services reserve before allocating energy to cooling, cooking or entertainment.

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