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How to Maintain Your Boat or RV Battery Over the Winter

Power - by Bryan Veldboom - updated on 9/29/2020

Boats in storage

For much of the country, Fall marks the end of outdoor activities like camping and boating. As you start making preparations to store your RV or boat for the off-season, it's important to maintain your vehicle battery's charge during the winter months. Otherwise, you might find yourself with a dead battery next spring. Here are our top tips to help maintain your RV or marine battery over the winter.

Breaking Down RV and Marine Batteries

Depending on your power needs, you may have multiple batteries in your RV or boat. Both RVs and boats require starting batteries to turn over their engines. If you use a lot of additional appliances like air conditioners and TVs for your RV or fish locators, depth finders and radios in your boat, chances are you have a deep cycle battery as well. It's also possible that you might be using a dual-purpose battery, which does a bit of both. Regardless of the battery or batteries that you use, you'll want to make sure that you are using a charger to maintain them when they are sitting idle for long periods of time.

Types of Battery Chargers

There are three different types of battery chargers, all of which work a little bit differently: standard chargers, trickle chargers and battery maintainers. Standard chargers deliver amperage to a battery at a set voltage. The important thing to remember about older chargers is that they need to be monitored and turned off manually to avoid overcharging your battery. Otherwise you can end up damaging your battery and reducing it's overall lifespan.

Trickle chargers help to avoid overcharging by providing a very low charge that "trickles" into your battery over a longer period of time. Like standard chargers, trickle chargers need to be monitored and turned off to avoid overcharging, although some of them are equipped with a "maintenance" or "float" mode that will switch them off automatically when your battery reaches a full charge.

Battery maintainers are automatic chargers that will stop delivering a voltage when your battery has reached a full charge. They continue to monitor battery voltage even after a full charge, and will restart the charging if the battery voltage drops below optimal SOC. Because of this monitoring capacity, a battery maintainer does not need to be monitored or manually shut off like a standard or trickle charger.

Finding the Right Battery Charger

The first thing you'll want to consider when shopping for a battery charger is your battery's chemistry. Identify whether your battery is flooded, AGM or lithium and select a charger that is rated for that chemistry.

You'll also need to identify the voltage of your battery and pick a charger designed for that particular number of volts. For instance, if your boat has a 12-volt deep cycle battery, be sure that the charger you choose works with 12-volt batteries. Finally, make sure that the charger's amp is not too big for your battery. A good rule of thumb to follow is that charger amps can't be more than 3/10ths your battery's capacity.

What are Some Good Battery Chargers for RVs and Boats?

The X2Power 7.5 Amp Charger is a great choice for your RV and marine battery needs. It charges both 12-volt and 24-volt batteries and is rated for flooded, gel, AGM and lithium batteries. Best of all, it is a battery maintainer, which automatically protects your battery from overcharging.

The NOCO GENIUS10 Automatic Battery Charger and Maintainer is another great option for charging 6-volt and 12-volt batteries. This charger is compatible with all types of vehicles and is ideal for marine, deep cycle and lithium ion batteries. You can also attach it to any battery without fear of overcharging; it will simply switch off once your battery reaches its ideal charge.

How to Maintain Lithium Batteries During Storage

Unlike flooded and AGM batteries that need to be kept as close as possible to a 100% charge during storage, a lithium battery should be stored at a charge of around 50%. Lithium batteries also have a very low self-discharge rate, which means that you probably won't have to charge them during storage. Nevertheless, you should still check them every few months and if your lithium battery has dropped below 30%, charge it back up to around a 50% state of charge.

How Long Does it Take to Charge a Battery?

In order to determine how long it will take to charge your battery, you will need to identify the battery's capacity in amp hours. An amp hour (Ah) measures how much amperage a battery can provide per hour. This information should be available on the manufacturer's website.

With this information in hand, look at the charger's amp capacity to determine how long it will take to charge your battery. For instance, a 75 Ah deep cycle battery using a 7.5 amp charger will take roughly 10 to 11 hours to fully charge, whereas a 10 amp charger would charge the same battery in about 7 to 8 hours.

Is it Better to Remove a Vehicle's Battery Before Connecting it to a Charger?

This depends on a variety of factors. Often times the battery itself may be too heavy to remove or you may find that your battery is housed in a difficult-to-reach location.

If it is not practical to remove the battery from your boat or RV, you should at least unhook it to help keep the terminals clean when it is not being used. An anti-corrosion spray is perfect for keeping terminals clean. Or, if notice you a build-up of corrosion, you can use a battery terminal brush with a solution of baking soda and water to clean them off. You should also keep the vehicle itself stored away from extreme cold or heat, which can hurt a battery's capacity over time.

If the battery can be removed, it should be stored in a dry area, away from major outdoor elements, particularly extreme hot or cold. A battery box is the perfect way to help maximize the life of your battery by protecting it from dirt, extreme temperatures, sun exposure and more.

Trust Batteries Plus for Your RV and Marine Battery Needs

Regular maintenance is key to getting the most out of your RV or boat battery. If you're concerned about your battery's performance, bring it to any Batteries Plus Bulbs to have it tested for free. If you end up needing a replacement, we have top-quality batteries for RVs and marine battery options available.

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