The short answer: at the start of the season, check the batteries first, then charging, then safety-critical circuits such as bilge pumps and navigation lights, and finally instruments and comforts. Winter damp does most of its damage quietly, so the point is to find problems on the berth rather than on the first sail.
Our winter checklist covers laying the boat up. This one picks up where that left off.
Charge the bank fully and let it rest before judging it. A lead acid bank that was left partly charged all winter may have lost capacity for good; a lithium bank that was stored correctly should come back without fuss. Clean and tighten terminals and check the batteries are still secure in their mounts.
Run the engine and confirm the alternator charges at the expected voltage. Plug in and check the shore charger does the same. If you have solar, look at the controller readings on a bright day. A source that has quietly stopped working is far better found now than halfway through a cruise.
Inspect the lead end to end for cuts, crushed sections and scorched pins. Look inside the boat's inlet for corrosion or discoloration. Test the RCD using its test button once connected. Any sign of heat damage means the lead or inlet needs replacing before further use.
Safety note: shore power is 230V AC. Faults on the inlet, RCD or AC wiring are a genuine shock and fire risk and should be dealt with by a qualified marine electrician.
These come before anything else on the list once batteries are healthy.
Power up the plotter, depth, wind and autopilot and confirm they talk to each other. Networks that worked in autumn can fail after winter damp gets into a connector. Update plotter software and charts while you are alongside with time to spare.
Lift a few panels and look at wiring in the damp parts of the boat: near the bilge, under hatches, behind the chain locker. Green corrosion, damp connectors or chewed insulation are all worth fixing now. A quick sniff of the battery and engine compartments after charging is worthwhile too.
If the list throws up several faults, or anything that smells hot, that is the time for a proper electrical inspection rather than piecemeal fixes.
Before relying on the engine, check the start battery connections, the starter motor cables and the alternator belt tension. Look at the engine wiring loom for chafe where it passes near moving parts or hot surfaces. Warning lights and alarms should come on during the start sequence and go out once running; a lamp that stays dark may hide a fault in the alarm circuit itself.
Run the engine long enough to see the charging voltage settle and to feel for any connection that warms up unexpectedly. A hot joint on a charging cable is far easier to deal with on the berth than at sea.
Jot down the readings you take: resting battery voltage, charging voltage from each source and anything that needed attention. Next spring, those notes let you compare like with like and spot a battery or charger slowly deteriorating over years rather than suddenly failing.
A simple log also helps when the boat is eventually sold. Buyers and surveyors respond well to evidence that the electrics have been checked methodically, and it shortens any pre-purchase survey conversation about the state of the system.
With the safety items done, work through the comfort loads: cabin lighting, water pump, fridge, heater, USB and 12V sockets. A water pump that runs on without a tap open points to a leak or a failing pressure switch. A fridge that takes much longer than usual to cool may simply need its condenser cleaned after a dusty winter ashore. Test the inverter, if fitted, with a modest load rather than the kettle, and confirm its low-voltage cut-off still behaves. Anything that fails this round is rarely urgent, but it is far easier to sort while you are still alongside with tools and parts to hand.
A couple of weeks before you plan to sail, so there is time to fix anything that turns up without losing the start of the season.
Possibly, especially lead acid left partly charged. Test after a full charge and rest before deciding.
Not necessarily every year, but a periodic inspection is sensible, particularly on older boats or after a wet winter.
We can check the electrics before you sail and fix anything winter has left behind. Free assessment, written quote.