Choosing the right hybrid power system

It is possible to run a boat using only electric motors powered by a battery bank. The battery bank can be charged by solar panels or by a shore charger. However if longer journeys are planned then a hybrid system should be considered.

Put simply, hybrid power is the combination of different technologies to produce power. In our case, these are an electric motor working in combination with a petrol or diesel motor that in turn runs a generator. There are 2 systems detailed below. Within these systems there are choices to make such as the size of generator and battery bank. Choice can be confusing but please don’t be put off – it’s really just a question of imagining your life on board and how you would use your boat.

In the serial system, a battery bank powers a large electric motor that turns the propeller through a direct shaft. The battery bank itself is charged by either the generator, shore power or solar panels. It is a very simple system and can be tailored to suit individual needs very easily. For instance, if you are planning long journeys it would suit to have a large generator. On the other hand if the boat was only going to be used at weekends, charging using the solar panels with a small generator backup would offer a low cost and more environmentally friendly option.

A parallel hybrid option uses a conventional diesel motor to turn the propeller via a direct shaft. An electric motor which doubles as a generator is connected in parallel to the prop shaft. When motoring at low speeds, excess power from the diesel motor is picked up by the electric motor which, acting as a generator, tops up the battery bank. Turn the diesel motor off and the electric motor can be used to drive the prop shaft. Batteries can also be charged via solar panels or shore power.

This system is slightly more complicated than the serial system and requires more maintenance however it suits owners that require a lot of power, for instance, those operating in tidal rivers for long periods of time.