Selecting A Marine Battery

4th Mar 2020

Selecting A Marine Battery

If you are all set on finding a new hobby, how about looking into getting a boat? Once you’ve got your vessel all set, you will be able to head out onto the water and enjoy a peaceful time bobbing over the waves. Don’t worry if simply relaxing on deck sounds too boring - you could also spend your time out on the water fishing or diving. Once you find a boat that’s right for you, you should find that there are various pastimes you can enjoy offshore.

When you are looking for a boat, you will have to find a battery to go with it. There are many reasons why you might need plenty of electricity on board your boat, not least of all to power it, so it’s worth looking for a battery that can provide you with all the power you will need.

Find the right boat battery, and your trips out to sea will go like a dream. However, if you get the wrong kind of battery, you might be limited to what you can do on board and it might not always be plain sailing. To help you figure out which is the best kind of boat batter for you, have a read through this blog post. We’ll cover all of the points that you need to think about.


Starting Batteries

You will need a starting battery to get your boat going. You’ll find that they generally provide between 75-400 amperes for 5-15 seconds and will then be continually recharged by your boat’s alternator. These are lead-acid batteries and often have more thinner plates than the other types of batteries. This allows them to create high bursts of current when you need it most.

There are some negative points about starting batteries, though, including the fact that they are quite fragile. This makes them unsuitable in environments were they are likely to suffer high impacts. Deep discharges will also reduce their lifespan.

Deep-Cycle Batteries 

The deep-cycle battery is often thought of as the boat’s house power bank as it powers all of the electrical loads when there is no other charge source available. These are often used as a backup and it’s often highly recommended that all boat owners invest in a reliable one.

These don’t generate high bursts of power, instead they can fully recover after being discharged over long periods of time. This is all thanks to their thicker plates. Overnight usage often uses 50-70% of the total charge - recharging the battery will add all of this back into the bank. It’s always best to find a deep-cycle battery that can store 3-4 times the expected amount of power needed for a boat.

Dual-Purpose Batteries

Dual-purpose batteries are another type that also have thick plates and are a good compromise between the two types of batteries above. They can handle deep discharges that would tend to damage a starter battery. They are ideal for the following situations:

  • Small boats that use a single battery.
  • Sailboats that use two identical batteries.
  • Boats that have one battery that does a double duty as they will last longer and are cheaper to run than other battery options.

Battery Chemistry

The majority of all batteries will come in four different chemical types. Generally speaking, you will need to choose the chemical type depending on the application of your battery. There are other factors that might influence your choice too, including your budget and the expected lifespan of your battery. These are the four to choose from:

  1. Thin Plate Pure Lead And Lithium
  2. Thin plate pure lead batteries (TPPL) are very advanced AGM batteries. The lead in them is extremely pure and rolled into plates rather than cast. Thanks to this, they are able to take high charges, more so than the average AGM battery. They charge incredibly quickly and are able to discharge to 80%. Many boat users who go on long-distance trips opt to use TPPL batteries as they can easily run a diesel engine for up to six hours.

    Lithium batteries weigh less than the lead ones and can discharge up to 800 times at 100%. They are super quick to recharge, and this usually only takes an hour. If you need a high-performing battery, then this could be your best bet.

  3. Flooded Batteries
  4. Liquid sulfuric acid is stored inside flooded batteries. When the battery is charged, this produces hydrogen and oxygen. This gas is then able to escape through vented wet cells and it then escapes into the atmosphere. If the batter box isn’t correctly vented then there is a risk of explosion as hydrogen is a very volatile gas.

    If you do decide to go with a flooded battery, you will need to carry out regular inspections and to always top up the water levels when they start to get low. One of the main benefits of these kinds of batteries is that you can overcharge them without worrying about damaging them. They do discharge at a higher rate, though, so you will need to carry out some off-season charging. Overall, flooded batteries are a very affordable option and as long as they are maintained correctly, they will last a fairly long time.

  5. Gel Batteries
  6. Some boat owners prefer to go with gel batteries over flooded ones as there are a few notable benefits. For instance, they discharge very slowly and can handle a lot more charging cycles. There’s also no maintenance for them and you don’t have to worry about them spilling. What’s more, they can survive being submerged and are completely leak-proof. There’s also a pressure-release valve that will allow them to release excess pressure if required.

    Thanks to the design of gel batteries, there is no risk when installing them in areas where people will be. They are also often manufactured to very high standards, so you know that you are buying a reliable battery.

  7. AGM Batteries
  8. AGM batteries have been mentioned a few times in this blog already, but what exactly are they? These are in fact one of the more common types of boat battery as they are seen to perform better than flooded ones. They are completely sealed and valve-regulated. Whilst charging, precision pressure valves let oxygen flow between the positive and negative plates. It then combines with hydrogen to create water. This, along with the fibers in the glass mats, provide plenty of support and protect against shocks and vibrations.

    AGM batteries with a high density have a low internal resistance and can allow for a greater starting power. They can also accept charges that are up to 45% of the batteries overall capacity. What’s more, they can recharge a lot quicker than most deep-cycle batteries. If you want a battery that will quickly recharge and provides you with a quick starting power, then go for an AGM.

Battery Ratings

As well as the type of battery and chemical makeup, there are also a few ratings that you will need to be aware of when you are choosing a new boat battery. Here are some that you should always look into:

  • Starting Functions
    This regards the power that is needed when cranking a starter. Different batteries will provide different charges.
  • MCA vs CCA
    CCA stands for “cold cranking amps” while MCA stands for “marine cranking amps”. Generally, MCA will be about 25% higher than CCA because the majority of batteries work better at high temperatures.
  • Reserve Minutes
    This rating will show you how long the battery will be able to sustain 25 amps before it will drop down to 10.5 volts. For example, if a battery has a reserve minutes of 150 minutes, then it will be able to keep at 25 amps for two and a half hours. If you are only looking for a starting battery, then this isn’t such a necessary rating to look at as they aren’t used to handle reserves for long periods of time.
  • Size
    What size cranking battery you will need will depend on a few things, including the size of your engine and ambient temperature. If you will be sailing in cold temperatures, you will need a high cranking power. Diesel engines and high compression gas engines will also require quite a sizeable cranking power. You also need to remember to meet the minimum CCA required by the engine manufacturer.
  • Deep Cycle Functions
    Amp-hours (Ah) and reserve minutes are used to express the battery capacity measurements. The former is the amount of energy a battery can deliver for 20 hours at a consistent rate of discharge before finally dropping to 10.5 volts. The latter is the number of minutes it can run before dropping to that voltage.
  • Longevity
    For most battery manufacturers, longevity means the time to discharge a battery at 80 Fahrenheit until it drops to 10.5 volts. This measurement is often called cycle life and it should give you an idea of how many discharges a battery should go through over the course of its lifespan. When you take a look at a few batteries’ longevity rating, it should be a useful way of comparing them to one another.

Improve Your Battery’s Performance

Of course, there are many ways you can improve the overall performance of your battery. You just need to follow these tips:

  1. Never mix old and new batteries in the same bank.
  2. Always stick to one type of chemistry.
  3. Keep boat batteries cool, clean, and dry at all times.
  4. Regularly check all of the terminal connectors to ensure good connectivity.
  5. If using a flooded lead battery, always add distilled water whenever necessary.
  6. Use a paste of water and baking soda to clean any corrosion on the battery.
  7. Make sure the charge voltages are regulated based on battery temperature.

By following these useful tips, you should be able to prolong your boat’s battery substantially.

As you can see, there is certainly a lot that you will need to think about when you are in the market for a new boat battery. As long as you read all of the information above, you should find that figuring out the best battery for your boat isn’t actually all that difficult.

If you do need anymore advice and guidance, then it’s worth checking with the Boater's Outlet team. You can also take a look at all the different boat batteries that we currently have available at the minute. Feel free to give our friendly team a call if you have any more questions about boat batteries as we will always be more than happy to assist you.