What electrical setup do I need for camping aboard a boat?

For weekend camping aboard, start with a separate 12V house battery, LED lighting, fused USB charging points and a way to recharge without draining the engine starter battery. A 100 to 120Ah lead-acid house battery usually covers modest overnight use without refrigeration; a fridge or several nights at anchor calls for more capacity and dependable charging.

Check wiring and calculate consumption

Identify the batteries, check their condition and establish which circuits each supplies. A large battery offers little comfort if the cabin lights can flatten the engine-starting supply. On older boats, check battery terminals, main switches, fuse holders and cable joints for corrosion, loose connections and heat damage before adding equipment.

Calculate consumption in amp-hours: divide watts by 12, then multiply by hours of use. A simple overnight budget might be:

• Three 3W LED cabin lights for four hours: 3Ah.
• A 3W LED anchor light for ten hours: 2.5Ah.
• Two phone charges, allowing for conversion losses: about 3 to 5Ah.
• Freshwater pump and occasional small loads: 1 to 3Ah.

That totals roughly 10 to 14Ah. Allow around 15 to 20Ah daily for comfortable basic camping, then add navigation instruments, fans and other equipment separately. A small compressor fridge commonly adds 20 to 40Ah per day, sometimes considerably more in hot weather. A thermoelectric coolbox can consume much more because it may run continuously.

Replace power-hungry incandescent cabin bulbs with LEDs early. For navigation lights, use an approved LED fitting or a replacement specifically suitable for the existing lantern.

Size batteries and protect starting power

Keep the starter battery dedicated to engine starting, with a separate house bank supplying camping equipment. An existing pair of healthy 75Ah house batteries provides 150Ah nominal capacity. To preserve lead-acid battery life, plan to use only about 75Ah routinely.

• Basic overnight camping: 100 to 120Ah deep-cycle lead-acid is a sensible starting point.
• A weekend with a fridge: consider 180 to 220Ah lead-acid or approximately 100Ah lithium iron phosphate, then check against your actual consumption.
• Several days away: size the bank for the longest likely gap between useful charging opportunities.

A 100Ah lithium battery typically provides around 80 to 90Ah of planned usable capacity. It requires compatible charging, a battery management system and protection against charging below its permitted temperature. It is not automatically a direct replacement for lead-acid.

For compatible lead-acid banks, a voltage-sensitive relay can connect them during charging and separate them afterwards. Lithium installations commonly need a suitably rated DC-to-DC charger to control alternator loading. Fit a battery monitor with a shunt, such as a Victron SmartShunt, to track consumption. Voltage alone is a poor fuel gauge under load.