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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’re excited about spending endless hours on the water and powering your trusted trolling motor and favorite fishing gadgets. But in order for your battery to continue working for years to come, you’ve got to put in a smidge of work to keep things running smoothly.

Now of course, 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. That’s because lithium batteries don’t need electrolyte “topping-up”, cleaning, or any of that nonsense that lead-acid batteries require.

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 the right way can actually affect your battery’s performance and lifespan. 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!

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 charger type.

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 means an ionic lithium battery will charge better with a lithium battery charger.

Sure, it’s possible to “mix-and-match” battery types and chargers. But you run the risk of your charger reaching different voltage limits than your battery can handle. 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, consider the fact that a correctly-matched charger will help your battery charge faster. For example, ionic lithium batteries 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. Built for lithium LiFePO4 marine batteries, they are smart chargers that supply constant voltage and stop charging once they reach max voltage. Some models may also be used to charge lead acid and AGM batteries.

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 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 and comes equipped with 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. If using a smart charger, you can “set it and forget it”. It will stop charging on its own. Ionic lithium chargers feature Bluetooth capabilities that let you check charge status on your phone. Other chargers, like those used for lead acid batteries, may require you to set a timer and disconnect it once it’s 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 adventure out on the water!