Boat Batteries: Everything a Boat Owner Must Know

Marine batteries for boats might be one of the most often discussed topics on boating forums. I used to have two marine batteries on my boat but after one started giving me issues, I realized I needed 3 boat batteries and a different setup. I did a ton of research on marine batteries and found a lot of questions that people had. As a result, I decided to put together this FAQ style guide to boat batteries and some of the most often asked questions. You've got questions, I've got answers! Marine Boat Battery FAQ: Should I leave my boat battery charger on all the time?How often should you charge a boat battery?Should I disconnect my boat battery? (when not using the boat)Does a boat battery charge while running?How do I know if my boat battery is bad?How often should boat batteries be replaced?Can you overcharge a marine battery? Can you recharge a dead marine battery?How long should I charge my boat battery?Can you use car battery for boat?Is there a difference between deep cycle and marine battery?What is a Marine Dual Purpose Battery?How do I winterize my boat battery?How much do boat batteries cost?Popular Marine Batteries Should I leave my boat battery charger on all the time? The answer to this very important question depends on what kind of charger you own for your boat batteries. 3 Stage and 4 Stage Battery Chargers If you have what is considered a “smart charger” then you have a piece of equipment that has some computer technology that will actually check and see what kind of charge is available in the battery and it will power off when the battery has reached the fully charged level that you are looking for. These are known as 3 stage and 4 stage chargers. Adakiit 6/12V 4A Smart Battery Charger/Maintainer Fully Automatic 8-Stages Trickle Charger for Automotive Car Motorcycle Lawn Mower Marine Boat RV ATV Sealed Lead Acid Battery 【MULTI-PURPOSES BATTERY CHARGER】6V and 12V Pb/SLA/VRLA/GEL/AGM lead acid battery charger tender, operated with vulcanization function, Adakiit battery maintainer charger is a great choice for lawn mower, boat, car, motorcycle, ATV, scooter, snowmobile, trucks (small), electric vehicle, electric tools, etc.( 4-120Ah)Used as Trickle Battery Charger as well.UPGRADED WITH 50A FUSE ONTO RING CONNECTORS8-STAGE SMART CHARGING - FULLY AUTOMATIC BATTERY CHARGER】8-stages automatic charging process [ Diagnosis - Desulfation - SoftStart - BulkCharge - Absorbtion - TestMode - Recondition - Float] by MCU controller,25%/50%/75%/100% to indicate quantity of electricity and monitor the whole charging progress.Stop automatically when the battery is fully charged.Perfect for year-round battery maintenance or long-term storage for improved performance and longevity.【INTUITIVE LCD SCREEN &INTELLIGENT DETECTION】The battery charger maintainer provides you status of the charging directly and diagnostic information, even when in maintenance mode.LCD screen displays charging voltage/current, charging mode, battery type and percentage of power remaining. When the charger is turned on, it restores the last settings used, making your life easier. It also automatically detects sulfated batteries and attempts to repair them if possible【MULTI SAFETY PROTECTIONS - BATTERY RESCUE & RECOVER】This battery charger offers multi protection against Reverse Polarity, Short Circuit, Over Voltage/Current, Over Charge/Discharge, Overload, Overheat; features Constant Pulse Current Maintenance function to avoid overcharge and discharge; Full-loaded and burn-in test prove its high reliable efficiency, stable performance【QUALIRY ENSURANCE Battery Maintainer】- Updated with battery condition diagnose to detect the defective battery before charge and 72-hour safety features, just get portable 6v 12v trickle charger for car batteries with confidence; Adakiit smart battery charger offer 2-Year quality assurance & 12-Month refund & timely after-sale services. $34.95 Buy on Amazon 1 Stage or 2 Stage Battery Chargers If you have a 1 or 2 stage charger, you have a more delicate piece of equipment that should not be left in the “on” condition for long periods of time. UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-Stage With Alligator Clips) For use with sealed lead acid batteries6V/12V switchable single stage chargerAlligator clips6V/12V Switchable Single-Stage with Alligator ClipsUPG D1724 Sealed Lead Acid Battery Charger $11.23 Buy on Amazon If you have one of these chargers, you should plug your battery in and charge it completely. Once that has been accomplished, you need to unplug the charger. The day before planning a trip, you’ll want to plug everything back in and charge up the battery again. If you leave your battery charger plugged in and it doesn’t have the recognition to turn itself off automatically, you may be causing some problems with the battery. It could dry up the cells found inside the battery which could actually overheat the battery and in some cases may even lead to a fire. Another instance where you probably do not need to leave your charger plugged in all the time is if you keep your boat stored on the dry land. Since there is no usage, it doesn’t really make sense to keep your battery and charger plugged in all of the time. On the flip side, if you keep your boat stored in the water, you’ll probably want to have access to your charger readily available because you will need the bilge pumps on your boat working. If you do store your boat in water, it would make a ton of sense to opt-in for a nicer boat battery charger that will make things more convenient for you. The smart chargers are not that expensive for the relative convenience they will add to your life. ProMariner ProSport 12 Gen 3 Heavy Duty Recreational Series On-Board Marine Battery Charger - 12 Amp - 2 Bank consumer electronics Increased Power & Performance...Heavy Duty Recreational Series On-Board Marine Battery Charger. Compact and rugged extruded aluminum design, dual in-line DC safety fuses for trolling motor and house battery banks. Built-in over-voltage, overload, over-temperature, reverse polarity and ignition protection.ProSport incorporates Distributed-On-Demand Charging technology, taking 100% of the available charging amps and distributing them to any one or combination of all batteries as needed for faster charging.ProSport is 100% waterproof and shockproof, weighing 40% lighter than older technology epoxy filled chargers providing cooler operation and greater reliability. Each ProSport model has 4 digitally selectable charge profiles including a once-a-month storage reconditioning mode for extending battery life.Advanced technology eliminates time consuming troubleshooting by clearly indicating system and battery connections are OK or if a fault is present on a specific battery bank.Fully charge and extend the life of your batteries. Automatically charges, conditions and safely maintains all batteries on board for maximum time on the water. Buy on Amazon Do you disconnect your battery before charging it with a Battery Tender? This is a simple question that has a complex answer. It is not necessary to disconnect your battery before charging it with a Battery Tender. However, these batteries perform similar to any other batteries that you may have in some of your devices. Basically, what that means is that it may not be the best decision to keep a Battery Tender hooked up to your boat battery to try and keep it at 100% all the time. As we know, batteries experience a lot of power loss when they are constantly being charged. This same situation applies here. If you try to keep things plugged in all of the time, you may see a loss of performance down the road that certainly would not be ideal. One good thing is that you should really not have to worry about any kind of instant damage or anything like that. The Battery Tender is designed to work well whether your battery needs a full re-charge or even if it is already completely full – you should not be damaging your boat if that is the case. When using the Battery Tender, you will find that it is considered to be a “smart charger”. That means that the Battery Tender will not cause any kind of damage once a battery is fully charged; it will simply send less power to the battery and it actually changes its “state” meaning that it will stop trying to power up the battery. It uses a combination of sensors and microchips to determine the batteries’ power so you never have to be concerned with anything dangerous. However, as mentioned, leaving the Battery Tender on for weeks at a time, for example, would be a great way to start to drain the life of your battery. How often should you charge a boat battery? Many people get concerned that they may not be using their boat battery enough, especially in off-seasons. There are some boat owners around the world who only may get the chance to use their boats for a few months out of the calendar year when the weather is nice – so when should they charge their boat batteries when they aren’t using their boats Generally speaking, you will want to leave your boat battery “fully charged” if possible. That means that you should not come off of a long boating trip and leave a “dead” battery in your garage for the entire winter. That would be considered mistreating your battery and really isn’t great for the life of your battery. You should charge your boat battery that you aren’t using about once a month. You could time it with some other task that you do once a month to make sure you don’t forget, like paying a certain bill. This regular timeframe will help to fight off any loss in battery life that may naturally occur over time. Another reason that you need to charge your battery in this kind of regular timeframe is that you will actually lose battery life over time, even when the battery isn’t hooked up to anything. This may seem like a kind of dark magic, but it is completely natural and you should not worry about the fact that your battery needs regular charge sessions even though you are not using it. Another tip for charging your boat battery would be to consider getting a smart battery charger. These smart battery chargers can help you by allowing your battery to stay plugged in. They will monitor your battery’s power and only charge it when necessary, meaning that you would lessen your involvement in the entire charging process. Should I disconnect my boat battery? (when not using the boat) Many boat owners try to figure out when the best time is for leaving their battery connected to their boat and when they should disconnect the boat battery completely. It’s a tricky question that will depend on your exact situation. The general answer is that you should disconnect your boat battery when you are not using the boat. However, you should only disconnect the battery if you store your boat on dry land. To me, that is what “not using the boat” really means. If you are someone who stores their boat in the water, you should not disconnect your boat battery from the boat. The important thing to know about a boat in the water is that the motor is not the only thing that the battery powers. There are other functions of your boat like the radio, bilge pumps, or various electronics like clocks that will be powered by this main battery. That may be hard to remember, but it’s similar to a regular vehicle in that sense. If you leave your battery plugged in, your boat will be draining your battery over time by the regular use of these items, albeit fairly slowly. If your boat lives in the water, you absolutely do not want to disconnect the battery. You’ll want to make sure that the boat has power in case it needs to use the bilge pumps when water rises inside the bilge. An ideal situation for a boat in the water is to use a smart charger that helps it stay powered all the time. If your boat is going to be out of the water for a few weeks, it is a smart move to take the battery out and make sure it is completely charged up. It would also be smart to give your battery a full charge the day before you are planning on using your boat again after a long hiatus. Does a boat battery charge while running? This depends on what kind of boat battery you have. Generally speaking, a boat battery does not work the same way as a car’s battery would, with some exceptions. Car batteries work as a “starting battery”, which may also be known as a cranking battery. Basically what that means is that car batteries are not used much once the engine is moving. Once your vehicle is traveling down the road, everything gets powered by the main engine. Most boat batteries do not operate like that. Most boat batteries are known as dual purpose batteries because they still help to power some of the things on board as they are in operation. However, these batteries also work as “starting batteries” which is why they are given the name “dual-purpose”, simply because they start the boat’s motor, but they also power different electronics after the motor is already running. In that sense, your boat battery will actually continue to be used as you are running your boat. This is the opposite of what most people expect from their car battery. The boat battery is really quite special because it is able to start your boat’s motor with a big boost of energy, but it also is able to deliver a consistent supply of energy to the boat’s electronics on board to keep those active as well. You’ll need to take proper care of your boat’s battery in between trips to make sure that you are getting the most out of your battery when you take your boat out on the water. You should charge your battery about once a month if you are never using it, and do not rely on your boat’s motor to start charging your battery once you are up and running. How do I know if my boat battery is bad? There are three main ways to know if your boat battery is bad and needs replaced. The first step that you should do is take a look at your boat battery. That seems obvious to some, but you are looking for a few things here. Any obvious signs of damage to the terminal may indicate that you have a bad battery including cracks or bumps in the plastic. If you see any kind of excessive leak or discoloring of the battery, these would also be signs of some kind of damage. If something looks really off, you may want to consider handling your battery with care as some of these signs may be a dangerous situation. The next way to figure out if your boat battery is bad is by taking a voltage reading. Generally speaking, you will want a voltage reading of over 12 to ensure that your battery is actually operating correctly. If you have a reading of 0, that would be a great indicator that you have a short circuit somewhere in the battery. If your battery seems to be fully charged but the voltage is still under 12, then you are probably dealing with a dead cell in your battery. You can also do a “load test” for your battery, although this is a more complicated method that most users won’t really benefit from. It’s important to take regular care of your battery just like any part of your boat, because you don’t want to have any unexpected problems when you are getting your gear together. You can also use a smart charger to help keep your boat battery at 100% all of the time so you can use it right away when you need it most. How often should boat batteries be replaced? Boat batteries can last a long time, especially if your are performing excellent maintenance checks and you have a high-quality battery from a reputable provider. In situations where boat batteries are well taken care of, then can last up to 7 years. This is the high end range of a boat batteries’ life, and it is not uncommon to see a boat battery last just a couple of years. There is no good way to predict how many charges or how many years one individual battery will last as there are so many factors involved in trying to make a calculation like that. One great way to keep track of your battery life would be to use a monitoring system. These monitoring systems can really help you to prolong your boat battery’s life and keep it running for years into the future. While you may not be able to have any control over the cost of a battery, you do have control over how you use it and what kind of beating you put on the battery. Batteries are a complex item that can be managed better than what most people put them through, which is why a system like Simarine can help you manage your boat batteries. If your boat battery has already died, you should take a few precautions when disposing of your battery. For one, you should not get rid of your old battery in the trash. It is best to recycle your old battery because it reduces harmful chemicals in waste and it lessens the impact of the creation of new batteries when your old one gets recycled. At the end of the day, you should take the best care possible to make sure your battery lasts for a few years and you get the value of a good purchase. Can you overcharge a marine battery? Yes, there are situations where you can overcharge a marine battery. If you use a traditional battery charger; you should take great caution to make sure that you are not over-charging your battery. For starters, any kind of improper use could cause you to see a lot of performance loss that will lead to worse battery function over time. However, there is a bigger concern when it comes to over-charging your battery which is that you may be damaging your battery. If your battery gets too much “charge”, it could overheat which causes problems with the acid inside of the battery. At an extreme level, it may even cause your battery to crack or explode, which would be as bad as you think it would be. However, there are some exceptions where this is not the case. If you are using a smart battery charger which will be labeled as a stage 3 or stage 4 battery charger; you probably do not have to worry about over-charging. These chargers are designed to “switch” stages when your battery is completely charged. That is great news because you don’t have to really put any kind of thought into how long you leave your battery charged. Even if you are not using your battery, it would not be considered over-charging to charge your boat battery on a regular schedule like once a month. Boat batteries can lose charge over time, which means that you should actually get them plugged in and charging regularly so you are not losing any life, or at a bare minimum so that you don’t try to start up a dead battery when you finally get around to using your boat. With these tips, you can keep your battery healthy and functioning for years into its life. Can you recharge a dead marine battery? Generally speaking, you may be able to use a battery saver to try to recharge a dead marine battery. There are a few situations where this will not work. If your battery has a short circuit or an open cell, you are not going to be able to do anything other than repairing that situation to fix your battery. These are unique cases, and require a completely different solution. However, for marine batteries that are simply dead, you may have a few recovery options. In this case, we will assume that you are referring to a dead battery as one that won’t seem to hold a charge. Obviously, you can re-charge a battery that has good battery life and has simply died with the normal charger that the manufacturer recommends that you use. If you are referring to a boat battery that has completely died, you may want to consider a battery saver product. There are a few of these on the marketplace, and they work by plugging in your battery for some different amounts of time. Some of them may even take days to work depending on the poor condition of your battery. You may also have problems because you are using a smart charger which may not recognize the true condition of your battery. Based on price, you may also consider buying a new boat battery if possible to get one of the best-functioning batteries that will give you a good sense of reliability. Regardless of what path you choose, you should make sure to take great care of the new battery by charging it regularly once a month and making sure that you use the best technology available. Smart chargers and battery maintenance programs are a great way to ensure that you are giving your boat battery the best chance possible at a long life. How long should I charge my boat battery? How long your boat battery should be charged for will depend on a variety of factors. For one, the time of charge will be impacted by how much life the battery has. Most boat batteries typically take a few hours to charge; although you should reference your manufacturer instructions to see exactly how long they recommend. If you have a battery that has been dead for a long time or has been sitting for a tremendous time; you should probably add in some extra charge time. One thing that should be noted is that if you feel that the battery is hot to the touch, you need to stop charging it. A battery should not be overheated or else there can be significant damage. One of the best ways that you can always know that your battery is being charged correctly is to use a smart charger. These chargers can be great for people who don’t use their boat regularly or may use their boat on an irregular schedule. If that sounds like you, you will probably want to use one of these smart chargers because you won’t have to worry about how long you need to charge your battery. One of the things that can decrease your charge time is taking care of your battery and making sure that you give it regular charges. It is best to give your battery regular charges to keep it performing at the best of its abilities. If you neglect your battery, it won’t last as long when using it individually and it also won’t last for as many years as it wears down from misuse. Always make sure to read the manufacturer instructions for your particular battery and follow their guidelines so you can maximize your battery’s life! Can you use car battery for boat? There are a lot of similarities and differences when it comes to boat batteries and car batteries. Car batteries are mainly used as cranking batteries. They are responsible for starting your car engine, and that’s about it. Once the car is operating and you are driving down the road at full speed, your car battery doesn’t really get used for anything. A marine battery is much different because they are supposed to start the engine but they will continue to provide energy once the boat is in operation. While both batteries operate on similar technology, it is not wise to try and switch usage between a car battery and a boat battery. First of all, there is no good reason to try and make this switch. Almost immediately, you’ll be voiding any warranties or any protection that you would normally have. This could only make sense if you are just trying to tinker around, and even then you really don’t have much of a beneficial reason to try and make it work. On top of that, you could potentially be putting yourself in a dangerous situation. While batteries can seem harmless, they are significant pieces of technology that can be dangerous to work with between the electrical current and any kind of battery acid that is involved. While it may seem like a good idea to try and save money by using a car battery with your boat, there is a much higher probability that you will end up costing yourself more money by creating some other kind of problem either with the battery you are using or with the boat itself which would come at a much higher cost. Boat batteries are specifically designed to do the job that they are named for, so let them power your boat and stay on the safe side that won’t cause you problems. What's the difference between marine battery and car battery?There are a lot of differences between marine batteries and car batteries. Car batteries are not designed to keep generating power to the engine once they are powered up, so they have much more thin internal plates. A marine battery is used to power the boat’s systems while the boat is in use. The battery gets continuously used, so it has to have thicker internal plates. While it may be surprising, marine batteries are also put under more duress during the lifetime of their usage so they have a lot of thicker design all over the battery to protect it from any kind of vibrations or impact. This makes a lot of sense if you think about it. Many people think about the possible impact of a car crash and harsh that can be, however the ocean is a lot bumpier than a highway and your boat actually takes a lot more of a beating than your car does. While the two batteries have similarities, you should never try to substitute one for the other. This is generally a bad idea that is going to cause a lot of potential problems with the operations of your vehicle. If you take good care of your marine battery, it should last you over the course of a few years which is well worth the price you’ll pay for such a battery. In that sense, they are similar to car batteries because those also last a long time. Marine batteries will need regular charging that cars don’t need because cars are essentially re-charging their batteries while driving down the road. You should charge your marine battery at least once a month to make sure that it is in good condition. Is there a difference between deep cycle and marine battery? There are some differences between traditional marine batteries and deep cycle marine batteries. The regular marine battery is a type of cranking battery which lets a boat start up by sending a lot of power to the engine and activating an ignition switch. The traditional battery sends short and strong blasts of energy to the motor to get it up and running. Cranking batteries have much thinner plates than those found in deep cycle batteries to make them work more effectively. These cranking batteries would be much less effective when trying to work as a deep cycle battery, so they are best when trying to complete their unique tasks. This is why using a deep cycle battery is extremely smart for boat owners. There are a lot of electronics and different things to power when operating a boat, and that’s where deep cycle batteries come into play. Deep cycle power batteries can keep all of your electronics functioning by providing power for them over time. They are more like other kinds of batteries that you see in daily life in that sense, as opposed to a battery that can start an engine. These deep cycle batteries are less likely to overheat than their other counterparts because they are designed to be functioning over long periods of time. You’ll also obviously receive better battery life when using them because you are not trying to rig something up that will be ineffective. It is best to use a marine battery to crank up your engine and get your boat moving, and then use a deep cycle battery to keep everything operating once you’re out on the water. With that combination, you will be getting the best use out of both batteries and you will minimize costs while optimizing the effectiveness of your setup. What is a Marine Dual Purpose Battery? Dual purpose batteries offer another option aside from using a deep cycle and a traditional marine battery to power your boat. Some people think that dual purpose batteries are the obvious choice because you minimize how many batteries you use, and these 2 in 1 options provide a lot of convenience in that sense. However, it is true that performance can be a little bit worse when you use a dual purpose battery as well. Because this dual purpose battery has to split its power between two different kinds of jobs, it may not work quite as efficiently as two separate batteries that are built to do those jobs completely perfectly. This becomes a matter of convenience versus power, and for a lot of consumers the fact that a dual purpose battery can get the job done on your boat will be enough to make sense to use them. It is the best practice to use these dual purpose batteries when you are trying to go on shorter trips because they may not hold up as well under conditions as two separate batteries would. Another tip would be to make sure that your dual-purpose battery doesn’t overheat. While not always a problem, they can be prone to overheating if they are in harsh conditions or if they are being overused. Whatever battery setup you decide to go with, you should be certain to always follow the manufacturer instructions to make sure that you are getting the best performance out of your battery. Some people think that they are too knowledgeable to read certain instructions, but there can be different warning signs and different benefits that you may not know about if you skip that reading. If used correctly, a marine dual purpose battery is a great alternative to the traditional options found on the marketplace. How do I winterize my boat battery? Trying to store your batteries for the Winter can be a hard task that you may not be familiar with. If you are a new boat owner or you are trying to squeeze some more life than you normally get out of your boat batteries, these are some of the best practices to follow when it comes to winterizes your boat batteries. To start with, you should always be performing regular maintenance on your boat batteries. If you start to neglect them, you will get worse performance over the life of the battery and it may not even last as long. To help winterize your batteries, you should be regularly watering your battery as well as removing any corrosion that is found on the battery itself. Before Winter comes, you should fully charge your battery. This helps you to start off with a full battery life when the time to use your boat comes back around. It also helps to negate the potential impact of a battery that freezes during the Winter time if you live in an area where that may be a problem. You do not want to check the gravity or voltage of the battery right away. If you need to check each cell of your battery, you should disconnect the negative cable and wait for hours before performing this check. That will help you get an accurate reading. You definitely do not want to leave any terminals connected to your battery that may drain their power over the Winter season. This drain can happen with a lot of different devices even if they are turned off. This is one of the biggest ways that people lose power both in the battery but also over the course of the life of the battery as well. Your batteries should be removed from your boat and you should put them somewhere that is dry and cool. They should also be removed from any kind of condition where they could freeze, so if you are keeping them out in a garage that is not heated, you probably need to keep them on wooden surfaces. As always, you should be regularly charging your batteries at least once a month. That helps them with the battery being drained and really keeps your potential charge a lot higher. How much do boat batteries cost? Obviously, there are a lot of different price points that you can find boat batteries. These prices may vary depending on if you are looking for a traditional marine battery, a deep cycle battery, or a dual purpose battery. Within the different price ranges, you will see marine batteries that cost as little as $100 and some that can cost higher than a thousand dollars. A lot of this depends on your varying needs as well as what kind of boat you are trying to power. Obviously, it wouldn’t make sense to put the same battery in an old small boat as it would in a more expensive and powerful one. You should check with your boat manufacturer instructions to see what size battery you need and what kind of batteries would be appropriate for your boat. The best thing to do if you are worried about the cost of your boat battery is to make sure that whatever brand you buy, you take good care of it. Regular maintenance is extremely important when it comes to boat batteries, so make sure that you store your batteries properly when they are not in use and that you take good care of them by recharging them once every month or so. You can optimize the charging of your boat batteries by using a smart charger. Popular Marine Batteries On Amazon SaleBestseller No. 1 Renogy Deep Cycle AGM Battery 12 Volt 100Ah for RV, Solar Marine and Off-grid Applications, Gray Maintenance Free: Manufactured with thick absorbent glass mat (AGM) separators and advanced valve regulated technology, Renogy Deep Cycle AGM Batteries save you from acid leakage and frequent maintenanceExcellent Discharge Performance: Proprietary quinary alloy plates and specially treated plate grids enable low internal resistance and high discharge currents of up to 10 times the battery rated capacityLong Shelf Life: Made of high purity materials, Renogy Deep Cycle AGM Batteries reduce the monthly self-discharge rate below 3% at 77℉ (25℃), which is 5 times lower than their flooded counterpartsWide Operation Temperature Range: Improved electrolyte formula ensures stable battery capacity and outstanding discharge performance at low temperatures below 32℉ (0℃)NOTE: We highly recommend installing the battery upright. 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Meets all EPA/OSHA marine requirementsAGM Battery, electrolyte suspended in fiberglass mat, specifically designed to be spill and leak proof. Excellent Resistance to vibration and shock, can be mounted in any position with long lasting performance.Dual purpose - works well for both starting and trolling $159.99 Buy on Amazon