Electrical systems on a boat

Marine electrical systems are very complex and availability of power is a key challenge on a boat. Power can be harnessed from a number of sources and MV Destiny is capable of using them all, depending on what is available at the time. Laying at anchor is different from being moored in a marina. Being in a large modern marina is different from being in a small port. Underway, the challenges are again different.

Shore power is available at marinas but has a number of challenges as the supply is not the same across the world. MV Destiny is configured to run on European standards of 230V at 50hZ. Some countries, notably the USA, run on 110V at 60hZ, so we can’t plug in to the marina power supply. Generators offer the most reliable source of supply as they are configured to suit the specific boat and are always available. However, the noise and fuel consumption makes them a less attractive solution on a permanent basis. A boat of this size runs mainly on AC power so when neither shore power or generators are available, we operate on high capacity inverters. An inverter converts DC battery power to AC mains power. Of course, those batteries still need to be charged up frequently (daily), so power has to come from somewhere.

Marine electronics and many other marine devices operate on DC power directly from the batteries. The battery bank is therefore the most critical part of the system and MV Destiny is equipped with an 800 Ah Winston LiFePO4 (lithium) battery bank, running at 24V. Batteries can be charged from AC power when available – from the generators or shore power. However, we also make use of sustainable energy by harnessing as much as possible from solar power and from excess power produced by the engine when we are running. We have installed an additional Balmar alternator on the engine which has higher capacity than the standard.

The electrical systems are managed and controlled by Victron Energy – the main control is from 2 x Quattro 8000 charger/inverters. These smart units will automatically switch between power sources when available and ensure that maximum power is available to the ship. Victron works together with REC BMS (battery management system) to manage the charging of the lithium battery bank in the most efficient way.

Lithium batteries have a lot of benefits over traditional AGM or gel batteries. Their expected life is much longer and they take up a fraction of the space and weight. In terms of charging, they can take whatever is thrown at them – and there is no need to be concerned about float charge and completing a charge cycle to preserve the life of the cells. The capacity of the lithium battery can also be used to a much lower level – they don’t gradually fade away as other batteries do. They are either working or dead – nothing in between! However, there are very strict rules about not over-charging them or allowing them to discharge too low. The bank is made up of 16 individual 3 volt cells, linked together to create an 800Ah bank at 24 volts. Each cell must be balanced so they are all synchronised – this is the job of the battery management system. The BMS also determines when charging is switched on and off to preserve the safe operating parameters of the bank.

The Victron Energy system also needs specialist MPPT chargers for the solar panels and a supplementary Skylla-i charger to boost charging capacity on AC power. The hub of the system is a Venus-GX control module which outputs data to any of our display screens via the video matrix. At any time, we can see the state of charge of the batteries, the consumption of the ship, the available AC power and any information we wish about any of the system components.

MV Destiny has two Northern Lights generators on board. The large capacity 26kW generator doubles as a get-home system (back-up engine) and is designed for heavy power demand peaks. The smaller 10kW generator is for the general day-to-day usage. The Victron Quattro will automatically start the 26kW generator when power demand requires it and shut it down when the peak subsides.

The electrical system comes together at a large breaker panel in the pilot house. The panel is floor to ceiling height and has:

  • 67 x 24V DC fused breakers and switches
  • 30 x 12V DC fused breakers and switches
  • 74 x 230V AC fused breakers and switches
  • 2 x Blue Sea selector switches to enable multiple power sources to be used for maximum efficiency
  • Safety panel with the main cut-off switches for all circuits
  • Various gauges and status panels to monitor the circuits

We designed and specified the breaker panel as well as the entire electrical system configuration. We also sourced most of the components in Europe and shipped them to the factory in China. This project consumed a huge amount of time to research and design, taking the different sources and outputs into consideration. The full details of this process and the rationale for the choices we made will be available soon as a full technical article.

The electrical systems also covers lighting and power outlets throughout the boat. We had to think about the locations for each mains power socket in the boat taking into consideration that there are a lot of constraints. The interior walls of a boat are sheets of wood – so you cannot install sockets in the locations you may want to. This project also took up a lot of time and discussion back and forth with the electrical foreman in the factory. In the end we have sockets in every conceivable location! These were also sourced by us in Europe from Vimar and shipped to the factory in China.

The lighting circuits were one of the few things on board which were not changed! We kept the standard location of all lights – there are a number of different types which will be covered in a detailed article shortly. Lighting includes not only the ceiling and atmospheric interior lighting but also under-water lights, deck flood-lights, navigation lights and exterior lighting.