Here are the ways to charge a battery pack on an electric sailboat.
When under sail, place the throttle in neutral with the keyswitch “on” when the dragging propeller rotates this will regenerate a power charge to the batteries . Hull Speed and Prop Shaft RPM dictate charging amperage. We have reports of 0-6 amp hours Regen at Hull Speeds between 3-7 knots.
We can put you in contact with an Electric Yacht “Family Member” with a similar boat in order to discuss real time Regen experiences.
Solar panels or a wind generator can be added to supplement regeneration and shore power charging. This is especially useful for moored boats. Solar, wind and/or regenerative charging can allow the boat owner to be completely free of the power grid and fossil fuel power.
Wind generator Solar panel
Shore Power Charging:
We highly recommend modern “smart” shore power chargers. Typically, these are microprocessor controlled chargers that sense the charge level of a battery and step down the charging current as full charge is approached. When the batteries are fully charged, they will turn off. This prevents over charging. If AGM or Gel batteries are used, a good quality charger designed for the specific type is a must. If the charger is a smart charger and the batteries require a three stage charge, be sure that the charger is set to bring the batteries up to full charge ASAP. This will include the programing the charger to charge the batteries when the batteries are above the “bulk” stage having not completed the “absorption” phase and moved into the “float/maintenance” phase. Having an AGM stay in a partial state of discharge until the battery is brought down to the bulk stage will walk the AGM battery’s capacity down.
Generators (dc or ac)
dc generators are the cruisers choice for rapid charging. The right size generator will allow the boat to cruise all day at the appropriate cruising speed without discharging the battery pack. Combined with the battery, you have full power at your command. Using an ac generator will require the use of chargers and power supplies to change the ac into dc. There is a loss of power in this conversion.