Marine batteries are specially designed for use on board, with a heavy steel plate and strong construction to withstand the vibrations and shocks that can occur in any powered boat. For this reason, marine batteries are generally more expensive than car batteries, which may tempt some boat owners to buy car batteries instead of marine batteries. Don’t make that bad decision. Marine deep cycle batteries last longer and perform more reliably than car batteries on board.
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Marine battery type
There are three basic types of marine batteries:
- The Ocean Start battery provides a quick but powerful injection of energy for a short period for starting the engine and is quickly recharged via the engine alternator. Starter batteries cannot be used for traction motors or electrical power appliances.
- Marine deep cycle batteries are designed to discharge slowly over long periods and withstand hundreds of charge-discharge cycles. Deep cycle batteries are the right choice to drive electric tug motors and other battery-powered accessories such as audio systems, windlasses, echo sounders, fish locators, and other equipment. Deep cycle batteries are not a substitute for starter batteries.
- Combining the performance of a start-up and deep cycle battery, the dual-purpose marine battery is a great option when you’re small and don’t have room for two batteries. While they can perform the tasks of starting batteries and deep-cycling batteries, they are not as efficient as individual batteries.
Deep Cycling vs. Crank Drive
You will need a separate deep-cycle RV battery if you have an electric towing motor, thruster, windlass, or other battery-powered accessories that can draw more current. Deep cycle batteries are only suitable for applications where high discharge and recharge rates occur frequently. Deep cycle batteries are constructed differently than crank batteries, with thicker, heavier plates. For example, the longer the time required for the towing motor and the windlass, the higher the amperage, which will heat and deform the thin plate of a common starter battery.
The crank battery has thinner plates to give a quick voltage spike to the engine but is not intended to maintain high power output for a long time. Yes, a deep-cycle battery can start your engine in a pinch. Still, a two or three-battery system is highly recommended to separate the engine battery from the accessory (indoor) battery.
The best way to ensure your battery is still good is to do a “load test.” Most auto parts or battery stores will test your battery for free and tell you if it still works. Just because it dies once or twice doesn’t necessarily mean it’s bad. Your other appliances and charging system may also need attention, as the battery may cause the problem.
Replacing the battery on your boat
When replacing your boat battery, consult your boat owner’s manual or your marine dealer, and be sure to buy a new AGM RV battery that matches your boat. Marine battery-rated ampere-hours, reverse capacity, and marine starting amps. When shopping for a deep cycle battery, you’ll want to pay the most attention to the amp-hour rating and reserve capacity. For starter batteries, the focus is on marine starter amplifiers. When searching for dual-purpose batteries, look at all three rankings.
Suppose you add electronic accessories to your boat. In that case, you may need to upgrade to a battery with a higher current rating, especially if you spend a lot of time running the engine at low speed (which will result in less power to charge the generator) or when you You’ll spend a lot of time at the beach or the anchor while using accessories like audio systems.
Charging marine batteries
When we buy a new or used boat, most of us know that the battery on offer doesn’t have to be top-notch. We don’t give them too much thought if they seem to be up to the job. But in warmer climates, daily heat is the main enemy of batteries and can drastically shorten their lifespan. In regions that force us to store our boats for the winter, maintaining the batteries during this time is also critical to prolonging life.
It’s best to put the battery on a regular trickle charger and keep it charged when not used. A battery that is not charging (or has been charging) can freeze at low temperatures, likely rupturing the battery case. Batteries are like many things in life – use them or lose them! Car batteries usually last longer than yacht batteries because the car is used a lot and the battery stays charged. Speaking of boats, there is an old saying that the battery life is two years, which is quite apt.
When it’s about to give up on you, you’ll usually get a warning that one morning the battery is “dead” or a bit slower to boot than you’re used to. You plug in the charger, the battery miraculously rejuvenates, and you’re ready to start your trip. You might think that a light was on or that the radio memory had dropped the voltage. The reality may be that the battery is sulfating, the negative is distorted, and it’s not charging like it used to.
Tips for Avoiding Battery Problems
- Use a good battery tray to hold the 12v lithium battery. The tray should have a base screwed or bolted to the boat and a rigid bracket or locking strap to secure it to the base. You don’t want your battery banging in choppy water.
- Check battery terminal connections frequently to ensure they are comfortable and corrosion-free. Replace the wing nuts typically found on marine batteries with nylon lock nuts, making them less likely to come loose.
- If you don’t use the boat often, use a maintenance battery charger to keep the battery fully charged between outings.
- Before off-season storage, fully charge the battery and disconnect the terminals so nothing can pull the battery off. If your storage location has electricity, keep your batteries on a battery maintainer/charger during the off-season. Otherwise, remove the batteries from the boat and store them where they can be connected to a maintenance charger.
- Install a cap or “boot” on top of the battery’s positive battery if it’s not a boatman installed, even if the battery is in a box with a lid. The start protects against sparks and arcs and possible explosions if, for example, a tool is dropped on the terminal.
Keep your batteries fully charged, keep your terminal clean, get out as much as possible, and “work out” your solar powered generator system as much as possible!
