Multisource charging

Alternative energy for the offshore yacht

- BILL MORRIS

If there is one thing we all seek when we slip the dock lines and set out for an offshore cruise, it is independence. For today’s cruiser, that means having all the modern comforts of life available at all times, wherever we go. Essential to our freedom is a robust, multisource charging network for our house and starter batteries operating while under sail or at anchor 24 hours a day.

Before running to your chandler and spending your cruising kitty on an ambitious list of charging devices, first determine what your battery charging needs will be, based on their rated capacity in amp-hours. A typical flooded 8D battery has a capacity ranging from about 200 to 450 amp-hours, with gel cell and AGM batteries lying somewhere in between. These large-capacity battery banks are charged one at a time to ensure adequate charging current, which is important to the health and lifespan of the battery.

The high-capacity 6-volt battery manufactured by Trojan — along with a number of lesser-known brands — is popular among offshore sailors, who connect two of the batteries in series to produce one 12-volt bank. A pair of Trojan T-125 6-volt batteries has a combined power rating of 480 amps while offering more installation flexibility than a single 8D bank.

Once you have established your amperage needs, you must design a charging system capable of keeping up with the demands of all your navigation and communications devices, along with lighting, entertainment, perhaps an electric windlass and — of course — the obligatory fridge. If you poke around a cruising marina these days, you will see that today’s fully equipped yacht draws power from solar panels, a wind generator, a hydro generator and an arrangement of controls to keep the battery banks topped off around the clock.