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Choosing A Marine Battery Charger

Choosing A Marine Battery Charger

By: SamComments: 0

Marine electricals can be one of the most complex jobs to carry out on board, and, with the sheer volume of information available nowadays, picking the right product can be tricky. That’s why we’ve created this simple step-by-step guide that will help you find the right marine electrical for your requirements.

What To Consider When Choosing A Marine Battery Charger

Do I need a 12V battery charger or a 24V battery charger?

This is the first question we ask anyone when they are looking to purchase a new battery charger.

As a general rule of thumb, 12V Battery Chargers are more suited to leisure users on smaller boats, where-as 24V boat battery chargers are often used on commercial and industrial vessels. However, on larger leisure boats you will often find 12 and 24V systems, as well as a 240V system that is used when you are connected to shore power.

The effects of voltage drops in 24V systems are minimized thanks to the increased power they offer and lower current in comparison with their 12V counterparts.

What are 12V Battery Chargers used for?

12 volt systems are typically used to power electronics like chartplotters, speakers as well as appliances like phone chargers. You will find that more systems run on 12V in comparison to 24V. See converters for more information on this.

What are 24V Battery Chargers used for?

24V battery chargers are used for appliances that require a little more oomph, for example fridges or air conditioning units.

Series vs Parallel:

Before we get onto Battery Banks, it’s worth taking you through the wiring options first, as this will impact the number of banks you require. In a series connection, batteries with the same voltage and amp hour capacity are connected to increase the voltage of the assembly. In a parallel connection, batteries of the same voltage and capacity are connected to increase the capacity of the assembly. We’ll explain this in the example below.

12V, 100A Battery + 12V, 100A Battery = 24V, 100A Battery Bank.

12V, 100A Battery + 12V, 100A Battery = 12V, 200A Battery Bank.

Do I need a 1 Bank, 2 Bank or 3 Bank Battery Charger?

To answer this question, we’d suggest simply ignoring the word ‘Bank’ and focusing on the number, as this is the amount of batteries that the battery charger will simultaneously charge. So a 1 Bank Charger will only charge one number at a time, whilst a 2 Bank Charger can charge two batteries simultaneously, and so on.

So if you have a 12V system and want to charge 3 batteries simultaneously, you will need a 12V, 3 Bank Battery Charger.

What Does A DC-DC Converter Do?

So you’ve opted for a 24 volt system but have an appliance that runs on 12 volts. Problem? Fear not. DC-DC Converters take the source of the direct current and convert it to another, so you can power 12V appliances from a 24V system. This works the other way too, so if you have a 12V system, the transformer within the converter will up the voltage to 24V – although this will use a lot more energy.


Now you have found the right DC-DC Converter, you’ll be presented with ampage options before going through with the purchase.

If, for example, you have 3 appliances that all use 5 amps – multiply the 3 with the 5 to get the total ampage that they will use. In this case, the total ampage that will be used is 15A, so we’d recommend opting for a 20A converter.

But I am only using 15A, why should I get a 20A converter?

We highly recommend not using the converter to its full capacity as this will increase the energy that it uses as well as the temperature of the unit.

An alternative option is to buy multiple converters with a lower ampage (for example, three 8A converters – however this is rare).

Battery Monitors:

Battery Monitors continuously monitor data including voltage, current, number of amp/hours, state of charge and the time to charge/discharge, making them an essential piece of kit that will enable you to use your marine battery more efficiently. This can enhance the battery’s lifespan and reduce the risk of failure.


An inverter converts DC (direct current) to AC (alternating current), which then powers your devices.

There are two main types of inverter - modified sine wave and pure sine wave.

Modified Sine Wave: 
Modified Sine Wave Inverters are cheaper but are less powerful and may produce some interference. Modified Sine Wave Inverters will not work with many appliances and use around 20% more power - as a result of this, they will be hotter and will not last as long as their Pure counterparts.

Pure Sine Wave:
Pure Sine Wave Inverters can power just about any AC appliance and are extremely useful for powering devices that can suffer from interference, like radios. The power produced by Pure sine wave inverters is cleaner, smoother, quieter and more reliable.

Renewable Energy:

Renewable forms of energy are rapidly growing in popularity, not just on land, but on boats too. When you add them to your boat, you will realise why! There are three main types of renewable energy for boats, we’ll take a look at them below.

Hydro Generators:
Hydro Generators contain an impeller that rotates when dragged through the water behind the boat. This rotation is applied to an alternator that produces AC power, that then produces a DC charge for your batteries. Hydro generators provide more consistent performance in comparison to wind and solar power options as they do not require on the weather, your boat just needs to be on the move.

Solar Chargers:
Solar Panels are the most well-known and popular choice of renewable energy. They are perfect for those sailing in warmer climates where there is regular sunlight. Furthermore, many solar panels can be walked on, enabling you to maximise space on board.

Wind Chargers:
Wind Chargers are perfect for those requiring extra power and provide excellent performance even at low wind speeds. Unlike solar panels, wind chargers do not require sunlight to perform at their peak, which is great if you are sailing in Britain!

About Pirates Cave Chandlery

Allow us to introduce ourselves..

We’re Kent’s largest chandlery, with over 10,000 items in stock at our Rochester store. Our crew of marine specialists have countless years of experience, so if you have any questions regarding battery chargers, or any other marine electrical, you can be sure to receive expert advice.

Our range of marine electricals have been carefully selected from leading brands including Dometic, Mastervolt, Nasa and Victron, so your next investment is the right one. If you have any questions, be sure to get in touch. Call us on 01634 295 233, send us an email or visit our Rochester store.


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