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How to Charge a Deep Cycle Marine Battery

How to charge a deep cycle marine battery
How to charge a deep cycle marine battery


The modern boat depends mainly on electrical power for approximately all of its essential functions from its onboard batteries. For marine/auto use, a deep cycle battery sometimes drops sufficiently below its required voltage to let your boat or its electronics run. And that is why you must own a special charger to energize your battery with its recommended voltage. The charging process of a marine battery is relatively quick and unproblematic. Here, we discuss how to charge a deep cycle marine battery.

Poor battery performance is often the unfortunate result of wrong charging techniques of batteries, paving us toward a significant limitation on enjoying success and making memories on the water. Even incorrectly charging a premium marine battery can be prone to a hazard in a quick amount of time. To avoid such unlucky murders, learning to feed deep-cycle marine batteries the right usage and charging process is quite easy.

How to Charge a Deep Cycle Marine Battery – The Process

Charging Procedure of a Deep Cycle Marine Battery

Terminal Cleanup

Going through the clean-up process of the battery terminals is not essential if there is no rust/corrosion, so you may skip this section. But if it is a requirement, get proper supplies/materials to avoid accidents. For this, use rubber gloves, protective glasses for your protection, paper towels, wire brush, and grit sandpaper to clean up the acid build-up.

When we say corrosion, we point toward a white, powdery substance that looks like it can blow away in the wind. This clean-up will eliminate the build-up and any probable poor connection between the feeder and the battery. Poor connectivity lengthens charging times with less available battery power.

Wear latex gloves and safety glasses for protection, and wipe away any excess corrosion with the wire brush. You need sodium bicarbonate/baking soda solvent to spray onto areas that are heavily corroded. Now, dilute 1 tablespoon of sodium bicarbonate in 1 cup of water in this solution. Wipe away the excess and, using sandpaper, thoroughly clean terminal posts off any remaining rust/corrosion.

Choosing the Correct Charger

Generally, before the beginning of any charging process, battery terminals are supposed to be cleaned. When it comes to charging, using a proper type of charger is the practical demand of any kind of battery, not just a marine one.

So, hunt for the correct charger type before the positive and negative lead engagement in a methodical arrangement to the positive and negative terminal. Purchasing the wrong charger type will surely be a huge waste because, besides not providing enough power for a full charge, it will promptly damage your battery.

A deep-cycle battery charger, more importantly, to reach full capacity, will render the appropriate amperage as well as the voltage for the marine battery in a timely fashion. Smart chargers are considered the best for marine dual-purpose batteries – starting and deep cycle.

This topper is also known as a multi-stage charger since the charging process includes 3-phases. Smart chargers own the technology to charge your marine battery, followed by its temperature and chemical structure.

The charger connection with the battery

The charging process can begin only in the absence of corrosion. Firstly, engage the marine battery terminals to the battery charger of the correct type. Placing a dumb charger with a battery will only increase the risk of lasting battery damage, costing its lifespan.

Here, a smart charter will deliver energy in 3-phases, including the bulk phase before the acceptance phase and the float phase. When plugged in, it maximizes the charge while preventing any damage at the same time to the internal components of the battery.

In case you do not own a smart charger, it costs about $50 to $100 for high-quality smart marine battery chargers, and we recommend it as it will extend the lifespan of your marine battery.

Charging the Battery

Here, we assume you have found the right charger type, so now engage the battery terminals with the charger clips. Switch on the battery charger after the connection, and charging should start.

At this stage, the charger will take the entire process in its management by adjusting the charging through the bulk method first and then to the acceptance method before moving to the float phases. With a smart charger, the battery’s charging percentage will be shown on the LED display. 

However, it is necessary to read manuals for the charger and the marine battery’s charging technique in case your charger is designed with adjustable charging settings before you set out for charging. Reading and understanding it will aid in processing the best speed for effective charging.

For an upperhand tip, a smart charger takes preventive measures against any damaging risk to the battery that may occur due to overcharging.

Removing the Charger

Shift the charger to the off position once you have a fully charged battery. Next, you must withdraw the charging clips attached to the battery terminals. The process will be finished after reattaching the lead back to cover the battery box before moving it back into the boat and enjoying its service. If you own another marine battery onboard, you can repeat the whole process to gain a full charge.

Battery Charging Cycles

Regardless of a typical marine deep-cycle battery’s design, it only allows a significant discharge depth. You can only spend a fraction of the actual capacity of the marine battery from consumption for many cycles before recharging it to its full capacity over its lifetime.

A normal cycle that a deep cycle battery is designed with surely starts at the full capacity (100%) and pushes a battery discharge down of about (20-50)% of the actual capacity before recharging it back to reach 100%. Their general depth of discharge also influences the battery lifespan.

A battery that frequents a 50% depth of discharge is expected to live longer than a battery allowed to go a greater discharge depth. Repeated shallow discharge down to 5-10% simultaneously shortens lifespan. Quality deep cycle batteries, from a pragmatic outlook, discharges as it is designed to before recharging it to full capacity.

How to Charge a Deep Cycle Marine Battery – Summary

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