What battery is best for Marine House Power in Power or Sailing Vessels?

The 12-volt DC system in a cruising powerboat is powered by a separate bank of ‘House’ batteries, which will be deep-cycled. The house batteries power GPS, electronics, radios, cabin and navigation lights, water, head and bilge pumps, and other dual power (AC/DC) appliances like refrigeration. The AC system is powered by ‘Shore Power’ or the on-board generator and supports items like electric stoves and ovens, TVs, cabin heaters and HVAC units. Dual power AC/DC refrigeration and straight AC loads like the microwave and TVs can also be powered by the inverter-charger.

The alternator charges house batteries after the starter batteries have been charged. When the boat is plugged into shore power or the generator is running, excess AC power is automatically shared with the inverter-charger, and the 12-volt house battery system is recharged. House batteries need to support the surge current of the inverter during load startup. State of Charge (SOC) monitoring will be advantageous.

The starting batteries must deliver high Cold Cranking Amps (CCA) consistently, operate at high and low temps and withstand vibration. With the engine off, High-Cycle Reserve Capacity (RC) is required to support special equipment such as winches, thrusters, etc. The engine alternator is the sole charging source for the starting batteries unless an independent shore-powered battery charger is installed. House batteries can often be connected to the engine to provide emergency starting. Maintenance-free spill-proof batteries are highly desirable in marine applications.

Deep-cycle battery specifications

Amp-hours (Ah); the current a battery can deliver for 20 hours at a constant discharge rate before the voltage drops to 10.5 volts. Cycle Life; Cycles represent the repeated charging and discharging of a full battery at 27°C / 80°F until the voltage drops to 10.5 volts and the battery fails to hold half its rated capacity. This ability to cycle repeatedly differentiates deep-cycle batteries from starting batteries or dual-purpose batteries, which can't withstand more than a few deep discharges beyond what they were designed for before their capacity degrade. Starting batteries are designed for maximum repeated discharges of 1-3% Depth of Discharge (DoD). Dual-purpose and high cycle batteries are designed for maximum repeated discharges of 17.5 – 30%Depth of Discharge (DoD). Depending upon technology, deep-cycle batteries are designed to withstand repeated depths of discharge of up to 50% to 80% Depth of Discharge (DoD).

Lead-acid battery failure is most commonly caused by acid stratification, extreme temperatures and destructive vibration. Acid stratification naturally occurs in flooded lead-acid batteries and leads to a decline in capacity and charge acceptance. AGM and acid mixing technology for flooded lead-acid starting batteries will mitigate acid stratification. AGM technology, or equalization charging by the inverter-charger for flooded lead-acid deep-cycle house batteries, will mitigate acid stratification.