The electrical system on a new Lombok boat should be boringly reliable: a 12 V or 24 V DC backbone sized from a real load budget, marine-grade tinned cable run high and dry, a distribution panel with proper breakers, batteries in ventilated boxes with charging matched to their chemistry, and solar doing the quiet daytime work that tropical sun gives away free. Most electrical misery on Indonesian boats traces to the same three sins — automotive parts in a salt environment, undersized cable, and no drawings — and all three are design decisions, made before the first wire is pulled.
Start with a load budget, not a parts list
Every sound system begins as a spreadsheet: each consumer, its current draw, and its realistic hours per day. Navigation lights, radio, sounder, bilge pumps, cabin and deck lighting, fridge, freshwater pump, phone charging for crew and guests — the daily amp-hour total falls out, and from it the battery bank, alternator and solar sizing follow arithmetically. A typical 12–15 m day boat lands around 60–120 Ah/day; a small liveaboard with refrigeration triples that. Skip the budget and you are guessing, and guessed systems die at anchor with a flat battery and a full boat.
12 V or 24 V — and when each is right
For day boats and most hulls under about 15 m, 12 V wins on simplicity: every pump, light and instrument in the Indonesian market comes in 12 V, every crew understands it, and single-battery redundancy costs little. Choose 24 V when the boat is longer (cable runs shrink to half the copper for the same power), when loads are heavy (windlass, big inverters, electric galley), or when the vessel will grow into liveaboard service — the class of build covered on the liveaboard build page. Mixed systems with a 24 V backbone and 12 V taps through converters are standard practice on larger hulls; what matters is deciding at design stage, because voltage retrofits are miserable.
The battery installation: where fires start and are prevented
- Separate house and start banks, with a voltage-sensitive relay or charger-splitter so the engine always starts no matter what the fridge did overnight.
- Chemistry chosen honestly: sealed lead-acid/AGM remains the rational default in Lombok — tolerant, available, serviceable island-wide. Lithium (LiFePO4) earns its premium on liveaboards with big daily cycling, but only with a proper BMS, matched charging and a supplier who will still answer in three years.
- Mechanical security: boxed, strapped, ventilated, above bilge water, with insulated terminals. A battery that moves in a seaway becomes a fire-starter with a handle.
- Main fusing at the battery — the one component that saves the boat when something else fails.
Wiring standards that survive salt air
The difference between a five-year system and a five-month system is mostly cable discipline. Tinned multi-strand marine cable, sized for volt-drop (three percent to critical loads), every run supported and chafe-protected, connections crimped with adhesive-lined heat-shrink — not twisted and taped — and everything labelled at both ends against a wiring diagram that lives aboard in plastic. Runs go high along the sheer clamp or deckhead, never through the bilge; the bilge is where automotive wiring goes to die. On desk-supervised builds the electrical installation has its own inspection hold point before linings close the runs, part of the staged checking described on the survey and inspection page.
Solar: the tropics’ free generator, done properly
Ten degrees south of the equator, solar is not an accessory; it is the day-time power plant. A pair of 200 W panels on a hardtop keeps a day boat’s house bank full indefinitely and covers most of a small cruiser’s hotel load. The details that separate real solar from decorative solar: panels mounted with airflow underneath (heat kills output), an MPPT controller rather than the market-stall PWM box, cable sized for the run, and shading thought through — a panel under a boom shadow all day is cargo. Wind and towed generation rarely pay at this scale; spend the money on another panel.
AC power, inverters and shore leads
Keep 230 V AC aboard as small as the mission allows. An inverter sized to the actual AC need — usually a fridge-safe 1,000–2,000 W — beats a big unit idling at a loss. Where generator or shore power exists, AC circuits need their own breakers, RCD protection and physical separation from DC runs, and the installation deserves a professional sign-off: AC mistakes electrocute, DC mistakes merely strand. For dive operations adding compressors, the compressor drive is its own engineering conversation — usually engine-driven or a dedicated genset, not the house inverter — handled in the specification stage of a dive boat build.
Navigation and monitoring: enough, not everything
A sensible Lombok fit: GPS/chartplotter, depth sounder, VHF, nav lights to rule, a battery monitor with a real shunt, and bilge alarms. The battery monitor deserves special praise — it converts electrical health from folklore to a number the crew can read, and it is the instrument that catches a failing charging circuit before the failure chooses its moment. Engine-room and systems instrumentation should mirror what the crew is trained to use during commissioning — the training rhythm described in commissioning weeks: training a crew on their new boat — because an alarm nobody understands is a buzzer, not a safety system.
What it costs and where not to save
Electrical typically runs three to eight percent of a new-build budget — modest against hull and engines, decisive for how the boat lives. The false savings are always the same: automotive cable, unfused circuits, one shared battery, and “we will label it later.” The genuine savings are design-stage choices: right-sizing the inverter, one voltage where one will do, and solar instead of generator hours. Where the whole budget sits by boat type is on the price and quote page; how the electrical stage slots into the wider programme is on the custom boat build page.
Specify the system on paper, inspect it before the panels close, and hand the crew a diagram they can actually follow — that is the whole secret to boat electricity that never makes the news.
Frequently Asked Questions
Should a Lombok boat be wired 12 V or 24 V?
Under about 15 m, 12 V usually wins: every pump, light and instrument in the Indonesian market comes in 12 V and every crew understands it. Choose 24 V for longer hulls where cable runs halve in copper, for heavy loads like windlasses and big inverters, or for boats growing into liveaboard service.
How much solar does a day boat need?
A pair of 200 W panels on a hardtop keeps a typical day boat’s house bank full indefinitely at ten degrees south. The details that matter: airflow under the panels, an MPPT controller rather than a basic PWM unit, properly sized cable and honest shading analysis — a shaded panel is cargo.
What kills boat wiring fastest in the tropics?
Automotive practice in a salt environment: untinned cable, twisted-and-taped joints, runs through the bilge and unfused circuits. The five-year system uses tinned multi-strand marine cable sized for volt-drop, adhesive-lined heat-shrink crimps, supported runs kept high, and labels matching a diagram kept aboard.
Are lithium batteries worth it on a Lombok boat?
On liveaboards with heavy daily cycling, yes — with a proper BMS, matched charging and a supplier who will still answer in three years. For day boats, sealed lead-acid or AGM remains the rational default: tolerant of imperfect charging, available island-wide and serviceable by any crew.