Cruising essentials, part 2, DC electricity

As I’ve said earlier, a major difference between weekend sailing and setting off to cruise the wide blue yonder is the requirement for self sufficiency. You’ll need to look at your systems and gear in a different light when faced with a lack of ready access to shore side facilities.

In particular you’ll need to carefully consider fresh water supply, electricity generation, maintenance and repair, sun protection, anchoring systems and safety gear.

DC electrical system: The considerations here are exactly the same as for your fresh water system – storage and supply; battery capacity and charging capability.

The biggest single user of electricity on a small cruising boat is refrigeration. If you have no desire for cold beer and crisp veggies you can get by with limited battery capacity supported by the standard alternator on your engine. Running an hour every couple of days should keep your electronics and lighting going nicely. Add a couple of solar panels and you’ll be truly independent.

If you intend to cruise in a warm climate and want to take with you a modicum of luxury – ice, cold drinks, fresh veg, butter and the like, you’ll need to beef up your power generation and storage systems. Throw in a water maker and extensive electronic navigation and communication systems and you’ll need to get really serious about making and storing amps.

So, calculate your daily consumption realistically and provide yourself with deep cycle battery capacity of at least four times this figure. Batteries should not be discharged on a regular basis to more than half their rated capacity, and you’ll want to give yourself a two day cushion so four times consumption isn’t excessive.

A typical small cruiser with a fridge would need around 100 amp-hours per day, half of that for refrigeration, so a 400 amp hour battery bank would be appropriate. A larger boat with water maker, fridge and freezer and extensive electronics will want considerably more, typically 600 to 800 amp hours.

Many boats have a separate engine starting battery and this is not a bad thing if you remember to keep it charged and you can spare the space. Having fuel in the tank and flat batteries is a frustrating situation. On Adriana I had no engine starting battery preferring two 200 amp hour banks for everything. On occasion I ran both banks almost flat but, fortunately, my Yanmar diesel would, with the decompression levers operated, rotate fast enough on the few residual amps to fire up and save the day. Had it failed to do so I might well have invested in a dedicated starting battery.

Having sufficient storage capacity is one thing, now you have to keep it topped up and a diversified charging capability has great merit. Most boats will have a means of converting fossil fuel to amps – some use their engine, larger boats tend to use a diesel generator properly plumbed-in and sound proofed; smaller boats might carry a petrol generator. If you mainly use the engine as your charging source, as we did for three years on Adriana, you’ll want to consider a high capacity alternator and a smart charger to make the process more efficient and minimise running time. Having to run the engine for a couple of hours a day can become quite intrusive.

Most sailors also take advantage of wind and sun – solar panels and wind generators, and occasionally water generators. Solar panels need careful thought regarding location and mounting methods (tilt-ability is good) but can provide noiseless, pollution free charging at practical rates. Wind generators can be cumbersome and noisy to neighbouring boats but in a good breeze can get the amps pouring into those battery banks. I’ve no experience with water generators – they are more useful to boats that are constantly underway rather than to my own stop and start nomadic lifestyle so I’ve never been tempted to try one.

I once saw a pedal powered generator, perhaps an option for the fitness fanatics among us.

Technology will continue to provide us with better and better DC systems for our boats because we have the same problems as do electric cars – power storage and replenishment. Lighter more powerful batteries and rapid charging systems are what we need. Fuel cells are already with us; their price will fall as demand increases. More efficient and more durable solar panels will become available and will, I suspect, increasingly replace wind generators as the preferred green choice for charging.