Stop Killing the Batteries

Your charter boat is essentially a large 12V battery bank. If you don't manage your power draw, you will destroy the batteries, spoil your food, and wake up to a low-voltage alarm at 3 AM.

The Power Hierarchy

12V DC System: Runs directly off the battery bank. Powers the fridge, freezer, lights, water pump, toilets, and navigation electronics. It is always on.
The Inverter (110V/220V): Converts 12V DC battery power into household AC power. Used for laptops, blenders, and small chargers. It is highly inefficient and drains the battery rapidly. Turn it OFF when not in use.
The Generator: Runs on diesel. Powers heavy AC loads: Air Conditioning, Watermaker, and the battery charger. You must run the generator to recharge the batteries if solar isn't enough.

The Fridge Crisis

The fridge and freezer are the largest constant 12V draw on the boat. If you open the fridge door constantly, the compressor runs continuously. The battery bank will drop below 12.0V by morning, triggering alarms.

Recharging Strategy

Run the generator (or main engines) twice a day: once in the morning to replace overnight draw, and once in the evening to cool down the cabins (AC) and top up the batteries before nightfall. Do not run the batteries below 50% capacity (roughly 12.2V on lead-acid AGM banks).

Inverter Load Estimator

See how fast a household appliance drains your 12V bank via the inverter.

Appliance

Usage Time (Minutes)

JavaScript required.

Fallback: A 1500W hair dryer pulls roughly 125 Amps from the 12V battery bank. This will crush a standard charter boat battery bank in minutes. Use the generator.

Common Mistakes

Mistake	The Reality
Running AC on the inverter	Unless you have a massive lithium upgrade, you cannot run Air Conditioning off the batteries. You must start the generator.
Leaving the inverter on 24/7	An inverter draws 2-3 amps just being turned on, even with nothing plugged in. Turn it off at the panel.