In this post: How to Charge a Deep Cycle Marine Battery
    Add a header to begin generating the table of contents


    LithiumHub batteries are built tough, from materials you can count on. But great quality is just the beginning. We’re constantly chasing after innovative ways to make our batteries safer, smarter, and more efficient.

    How to Charge a Deep Cycle Marine Battery

    battery sizes

    How to Charge a Deep Cycle Battery Properly

    Fisherman driving a gray and blue bass boat on the lake.

    Wondering how to charge a deep cycle battery the right way? You’ve come to the right place!

    So you took the plunge and invested in a deep cycle battery. You can’t wait to spend time on the water and use your trolling motor and fishing gear. But if you want your battery to last for a long time, you have to do a little work to keep things running smoothly.

    That said, if you have a lithium deep cycle battery, your maintenance “to-do” list is pretty short. Nearly as short as Santa’s naughty kids gift list. They don’t need regular cleaning and electrolyte top-offs like lead-acid batteries do.

    However, there is one thing you must do for any battery–even lithium. You must charge it the right way!

    Why Do You Need To Charge Your Battery Correctly?

    Why does it matter how you charge your deep cycle battery? Well, charging your battery the right way can affect how well and how long it lasts.
    For lead acid batteries, overcharging can ruin them. Leaving them at a partial state of charge can do a real number on them too.

    Luckily, those no-nos don’t exist for lithium marine batteries. You can use them past 50% battery capacity without damaging them. And you don’t have to charge them right away after using up your charge. This is super convenient when coming home from a fun but exhausting day out on the lake.

    But there are a few things you’ll want to keep in mind when charging a deep cycle battery, even if it’s Ionic lithium. Read on to find out how to charge a deep cycle battery the right way!

    Cycles of Battery Charging

    During its lifetime, you can recharge a deep cycle battery to full capacity many times. You can drain it down a long way and then recharge it to full capacity many times. You’d typically start with the battery at 100% capacity, then drain it down to between 20% and 50% of its capacity. And then recharge back up to 100%. No problem.

    The normal depth of discharge of your batteries will also affect their lifespan. To make a battery last longer, you need to push it to 50% of its capacity, and often. Repeated shallow discharge (5-10%) of a deep cycle battery reduces its lifespan.

    A good deep cycle battery can be drained and then recharged to full capacity. You don’t have to be very conservative with your batteries when you’re on the water. Drain them, and when you get back to dry ground, recharge them with a LithiumHub charger to restore their full capacity.

    How to Charge a Deep Cycle Battery Correctly

    Two fishermen driving in a red bass boat on the lake.

    Ready to juice up your battery? Here’s how to charge a deep cycle safely and efficiently:

    Choose the correct deep cycle battery charger.

    It’s a no-brainer that the BEST charger for a deep cycle battery is the one that’s built specifically for its type. That is, a lithium battery charger will charge an Ionic lithium battery better.

    Sure, it’s possible to “mix and match” battery types and chargers. But you run the risk that your charger could reach a voltage level that your battery can’t deal with.
    It’s possible to damage your battery, or at the very least, you’ll see an error code and your battery won’t charge.

    Also, keep in mind that the right charger will help your battery charge faster. For example, Ionic lithium batteries (and Ionic marine batteries specifically) can take a higher current. They charge much faster than other types, but only when paired with the correct charger.

    So how do you choose the right charger? Simply put, read the charger’s description. It will specify what type(s) of batteries you can use it to charge. For lithium deep cycle batteries, we suggest Ionic single chargers and Ionic bank chargers. These chargers are for LiFePO4 marine batteries. They’re smart chargers. They charge at a steady rate, and they stop charging when the batteries reach their full voltage. Some models may also be used to charge your AGM and lead acid battery.

    Onboard deep cycle battery chargers – the options.

    The Ionic 4 Bank Charger and the Ionic 2 Bank Charger are the two types of onboard chargers offered by LithiumHub.

    Both offer the same set of key advantages:

    • Charge your batteries more quickly and conveniently.
    • You can charge up to four 12V lithium batteries at the same time.
    • You can charge both lead-acid and AGM batteries.
    • The cable is five feet long.
    • View charge status via colored LEDs.
    • When utilizing Ionic Lithium Batteries, the Ionic Lithium app displays the charge level.
    • Lightweight
    • Affordable

    These onboard chargers are perfect for competitive fishermen and boaters. They’re also ideal for folks who want the most advanced onboard battery charger available. And people who hate to wait long for their batteries to charge.

    Portable chargers for lead acid batteries & lithium deep cycle batteries – the options.

    Sometimes, installing an onboard charger is impossible or impracticable. Take, for example, a small boat with limited storage space, or a kayak or canoe with a trolling motor. In these cases, you might need a portable battery charger. It’s probably impractical otherwise, and that’s okay — you’ve got options. LithiumHub has two types of portable chargers:

    These chargers are single-bank chargers, offering the same basic functions. These “Smart” chargers are for 12V LiFePO4 or lead-acid batteries. They’re constant current, and constant voltage (CCCV). When 14.6V is achieved, these smart chargers cease charging.

    Both are good choices for fishermen and boaters who need to charge their batteries on the go.

    Choose the right charger voltage/amps.

    Once you know what type of charger you need, you need to pick one with the right amount of voltage and amps. For example, a 12V charger is compatible with a 12V 100ah battery. Within the 12V battery category, you can choose from different charge currents (i.e. 4A, 10A, 20A).

    To choose the right amount of amps, check the amp hour (Ah) rating of your battery. Make sure the amp rating isn’t higher than the amp hour rating of your battery. Using a charger with an amp rating that is too high can damage your battery.

    You can also use a bank charger to charge multiple batteries at once.

    Charge in the right conditions.

    Did you know that high and low temperatures can affect your marine battery? Lithium batteries are the most resilient of the bunch. You can charge them at temperatures between -4°F – 131°F (0°C – 55°C) with no risk of damage. But the optimum charging temperature for Ionic Lithium Batteries is above freezing. If you need to charge your battery below freezing temps, no need to fret. Our 12V 300Ah battery is a beast of a battery. It has a heater, so no more worries about freezing temperatures!

    Two fishermen driving in a bass boat on the lake as the sun sets behind trees in the background.

    How to Charge a Deep Cycle Battery Correctly (& Safely): Step by Step

    Once you have the right charger, charging your battery is a cinch. Here’s what to do, step by step:

    1. Make sure the battery terminals are clean.
    2. First, connect the red (positive) cable to the red terminal. Then connect the black (negative) cable to the black terminal.
    3. Plug in the charger. Turn it on.
    4. Using a smart charger, you can “set it and forget it”. It will stop charging on its own. It’s easy to check the charge status of your phone on an Ionic lithium charger because it has Bluetooth. Most lead acid chargers require setting a timer and disconnecting the charger when the battery is charged.
    5. To disconnect, unplug the charger. Remove the black cable, then the red one.

    Now you know how to charge a deep cycle battery safely and correctly. Here’s to many more adventures out on the water!

    Deep Cycle Battery Charging Quick Answers

    Do deep cycle batteries need a special charger?

    Yes, you do need a special charger (preferably a smart charger). One made specifically for deep cycle batteries. Deep cycle batteries aren’t designed to handle the excess heat and rapid charging of a regular/traditional battery charger.

    What do I need to charge a deep cycle battery?

    It depends on your setup. As a competitive fisherman, your smart charger should have these attributes:

    • Priced fairly – affordable
    • Lightweight so you don’t lose speed
    • Charges your batteries faster than average
    • Can charge multiple 12V lithium batteries at once
    • Can be used to charge both lead-acid and AGM batteries.
    • Shows charge status via colored LEDs
    • When utilizing your batteries, an app that displays the charge level on your phone

    The Ionic 4 Bank Charger and the Ionic 2 Bank Charger are options that fit this description.

    Will an outboard motor charge a deep cycle battery?

    In most cases, yes. Most outboard motors can charge a deep cycle battery, much like a car charges its battery.

    Need lithium golf cart batteries? Shop here!

    Headshot picture of Martin Koebler, founder and president of LithiumHub.
    About the Author: Martin Koebler

    Picture a world powered by the hum of lithium batteries – in our homes, gadgets, vehicles, and more. Martin Koebler, our founder, has spent decades making this world a reality. His groundbreaking work in lithium battery technology is changing how we see energy storage. Learn more about his journey and vision here.

    Checkout more of our recent posts

    Lake and boats in marina in the winter, with LithiumHub logo on the side of the image.

    Avoid Costly Repairs: Winterize Your Bass Boat Like a Pro

    Winter is coming, and it’s time to prepare your boat for hibernation. Not only will winterizing your boat protect your ...
    Parked RV with a beautiful sunset behind it, and a LithiumHub logo on the side of the image.

    Free RV Parking 101: Essential Tips and Locations

    Picture this: you’re on a road trip, exploring the country in your RV, and you’re looking for a place to ...
    Man looking down into the hole in the ice, with an ice auger lying behind him, and LithiumHub logo on the side of the image.

    Finding the Best Lithium Ice Fishing Battery for Your Needs

    Amidst the freezing temperatures, ice fishing is a unique and exciting challenge, making it all the more rewarding when you ...
    Shopping Cart