Boat Electrical Questions

This indicates that the alternator is not producing a charge. Ensure that the ignition is switched to the "run" position, check the drive belt. Possibly, the alternator is faulty.

This is often an indication that the alternator is developing a fault.

This is often a sign that the batteries are failing. Battery banks should be replaced as a whole as a poor battery will act to suck power from a good battery if you replace only those units that have failed and connect new ones to old ones. Kingfisher can supply and fit new batteries for you and properly dispose of the old ones. Before buying new ones though, double check that there's nothing on the boat that is being left on and discharging the batteries.

This is probably a faulty connection, blown fuse or broken battery isolator switch.

This could simply be flat batteries. A fully charged 12v battery should produce 13.7v or thereabouts. 12v is considered to be nominal and 11v is flat. Many fridges and heaters systems won't work below 10.8v but lights and pumps will just suck the power until the battery can't give any more which results in the dimming. Worse though is that flattening a battery like this (especially if it's a standard lead-acid battery) is that it does the battery no favours at all and your engine will struggle to charge it. You'll probably have to charge it using a mains charger.

This is a common complaint with many possible causes and solutions. Firstly, if you or anyone else has recently adjusted any of the electrical system (added new electrical items perhaps?) begin there. This may be a case of failing batteries (which you need special tools to properly test), a failing alternator, broken cable or connection, failing charging relay or splitter and so much more. The first thing to check is the security of all connections. Kingfisher would be happy to trace the faults for you and can supply and fit new components (batteries, alternators, cable, etc) to overcome the problems.

There are many regulations that are often ignored with mains power on a boat. After 14 years of the Boat Safety Scheme, only now is it beginning to pay any particular attention to 240v mains systems, but we anticipate that inspection and subsequent failure notices will become common in the next few years. When this happens, the most common of installation mistakes are likely to cause great expense to the boat owner, so, please get it right from the start or have a BMEA-certified Marine Electrical Technician carry out the work for you. The regulations and safety information is quite involved and outside of the scope of a Q&A here, but ensure that you do not use solid core cable, do not bunch 12v and 240v cables together, ensure there's a RCD consumer unit and a proper earth. Plus so much more. Remember, get this wrong and you're playing with 240v mains AC power which has the instant ability to kill.

This depends on what you're installing. If you have a proper marine diesel generator, it may be relatively simple as these are often encased in their own sound-muffling housing which only needs to be mounted and have fuel, exhaust and power lines run to it. If we're talking about a low-cost petrol generator that's meant more for land-based work; stop right now. Honestly, this is not a job for a DIY boat owner without any real experience.

This is a great idea but a bit out of the scope of a Q&A. You'll need to work out how much charging you'll want to achieve in order to select suitable panels and a suitable charge controller. Consider this in conjunction with the length of time you're often away from the boat, the size of the battery bank(s) that you're charging (in amp hours). Never install solar panels without a suitable charge controller or you may damage your batteries and/or other sensitive equipment on the boat. If you're looking to permanently fix the panels to the roof, ensure that you properly seal all the fixings and holes from the rain using a suitable marine grade sealant/silicon to prevent water ingress. Connect your charging lines to the switched side of the battery isolators to comply with safety regulations.

Absolutely normal. Three way fridges are frowned up on boats these days. You're no longer permitted to install them under Boat Safety Scheme regulations. The system works in the same way for all three power methods; basically, you're applying heat to the external elements of the cooling system so that it draws heat from the chiller cabinet. The heating elements draw a fantastic amount of power from batteries which makes the system quite unsustainable in terms of maintaining charge. We would thoroughly recommend upgrading to a modern marine refrigerator.

Boat Lighting

Many boats were never designed to have the kind of lighting flexibility that you have at home. The fixed ceiling lights are often inadequate for task work but too bight for just lazy lounging. Changing lighting is often a long winded process as it's often the light fittings themselves that need attention and that means moving or replacing them which will leave mounting holes and other marks. So, perhaps then you need to look at designing new lighting as part of a minor refit where ceiling and other panels are replaced as part of the job.

In some cases, it can be as simple as changing an old incandescent bulb for a LED one with the same fitting. We can supply a range of bulbs to deal with this. If you have fluorescent fittings with long tubes, these can have replacement bulbs too, but the cost of these is very high and, if possible, you'd be better to replace the fittings. Many boats have 2D fluorescent light fittings (the square ones) and we can retrofit these light fittings with LED arrays.
The principal benefit is massively reduced power consumption. On board, ensuring that you have enough power is always a concern and reducing your consumption is always on a boat owner's mind. LED lighting saves a huge amount of power over incandescent, fluorescent and halogen bulbs. Some people don't like the colour cast from LED, but you will soon get used to it and, remember, there are various colour options anyway.
Not necessarily. In general, it is the type of LED that determines brightness rather than quantity. It's reasonable to suggest that for most LED bulbs, if you have more LEDs in a light, they are there because, individually, each one isn't that bright, but collectively they work well. The most accurate indicator of the brightness of any LED bulb is it's Lux or Lumens figure but don't confuse these two figures either; they are different things. Lux is a measure of how bright the light will be on a surface at a specific distance whilst Lumens if the amount of light the bulb can emit. This is further confused by the simple fact that these two measurements have never been used on other bulb technology which makes comparison particularly difficult. This, however, may not be a particular issue on your boat where the space to be lit is much smaller than a house with higher ceilings and so on.

Let Us Help

Kingfisher Boat Services has a wealth of experience in dealing boat electrical matters. We have BMET certificated personnel who can make sure that your electrics are safe and up to standard

Many people believe that 12v electrics aren't dangerous. Please be assured that the danger of fire is ever present if something goes wrong. You may not be thrown across the room if you come into contact with 12v DC, but that's no indication that it's "safe".

Boat electrics are often viewed as a simple DIY area. But, if your true knowledge of electricity starts and ends with replacing the batteries on the TV remote, please don't adopt a Jeremy Clarkson attitude of "how hard can it be" and attack your boat's wiring.


Please use the information on our Frequently Asked Questions pages as you see fit but at your own risk. We have a wealth of experience in these matters and are happy to offer this information free of charge, but by using any of details given on this page or other pages within this web site, you agree that you are doing so at your own risk. Kingfisher Boat Services cannot be responsible for any losses caused as a result of following any information given here.