How To Charge A Deep Cycle Battery Properly?

When it comes to power, we want the most out of our batteries. The only way that's going to happen is if you know how to charge properly a deep cycle battery and what they are used for. That’s why this article will discuss what is a deep cycle battery and learn some great tips on how to charge it properly!

What if you are told that deep cycle batteries can power an RV for more than just two days? Imagine your camping experience without the hassle of dragging around an electrical cord.

These batteries are typically used in RVs and boats to power their internal lights during long periods away from an outlet or when stationary somewhere like on camping trips.

For those of us who love to take outboards and boats, the battery's power is just as important as its size. You can't start a boat engine without high amps!

Deep cycle batteries are different internally, and how you charge them is also different. For instance, they need to be charged slowly so as not to damage the battery cells by overcharging or under-discharging them. Burst-type batteries need a faster charging rate for their higher power storage capacity (like your smartphone) can last longer when used continuously.

How To Charge a Deep Cycle Battery Properly?

Know the proper charger based on the type of battery (AGM, GEL, or flooded)

To charge a deep cycle battery it is important to select the correct charger for your battery. Choosing a poor quality or incompatible charger can cause irreparable damage to it, and you may have trouble finding replacement parts when needed in case of emergencies.

The chargers that they design for flooded cell batteries can charge them quickly at a high ampere rate. This can damage AGM and GEL batteries, so make sure you have the right charger.

Some people believe that a regular and deep cycle battery charger is the same thing, but this isn't true. A flooded battery can charge at a higher rate than GEL or AGM batteries. This means they will become fully charged in less time!

Use a deep cycle battery charger

There are two types of power cells that are designed differently, so it’s essential to use their specific setting to charge your battery correctly and avoid damage.

The chargers designed for AGM batteries are different. They use much less power, but the battery is charged at a slower and more stable rate. This contrasts with the charger for flooded cells which can charge them quickly but in a higher amperage.

Use of regular charger

Chargers for regular batteries are great for a quick recharge but can be bad news if you have an AGM or GEL-style battery.

They usually use high amperes to charge quickly; this is fine with flooded batteries but fast charging will shorten the life span of AGM or GEL batteries.

It's not recommended at all when using them-especially considering that there might also be problems getting 100% charged due to excess heat inside the battery from overcharging (and again, any issues causing more stress).

Battery Charger

The battery charger should supply around a maximum of 10% amperes your batteries can handle. If you have a 100 amp-hour rated battery, it will need up to 10 amps from the charger for good charging efficiency.

How long does it take to charge a deep cycle battery?

For the best charging experience, get a battery charger that will do it for you. This is now recommended by most experts and manufacturers as the safest way to charge your batteries. You'll never have to worry about over-or undercharging them again!

If you can’t find a suitable smart charger for your needs, then it's time to do some math! The easiest way is by dividing the output of the battery.

For example, with 10 amps as input and 100 amp batteries needed though; that means charging them in ten hours will be necessary.

Steps to Connect to a Battery Charger

Step by step guide on how to charge the battery directly:

  • Make sure that the battery terminals are clean, free from grease and dirt. Use wire wool if needed.
  • The cables should be connected tightly to the battery terminals as this will ensure that they are not loose and can cause a short in the system.
  • Remember to connect the red (positive) cable first. Then, you'll want to plug in your black wire(negative).
  • Plugin the charger and switch it on. Take a moment to make sure the indicator is charging if it has one.
  • The idea of a smart charger will tell you when its charging gets completed. A non-smart charger requires manual input and remembering to disconnect after the charge time is calculated.
  • When you want to disconnect the charger, unplug it first. Remove the black cable followed by the red cable.

The Alternators

Alternators are great for topping off a battery's charge, but when batteries of different capacities have to be connected in parallel it can cause a voltage drop which may lead the system to malfunction. Outlined below are two solutions if there's a mismatched capacity between strings - either by installing one new higher-capacity battery or adding an external charger and running both systems at once.

Use of Isolator

The isolator is a device that can charge your batteries separately so you don’t have to worry about the accessory battery draining and making an engine-powered car unusable. The way it switches from one charging mode to another keeps both of them healthy, too!

Tool - 'pro mariner 130'

The ProMariner digital mobile charger 130 is a device that connects your alternator to batteries and includes smart software, so each battery receives the correct amperes.

Charging A Boat Battery While On The Water

To keep your boat battery charged while on the water, you can use solar panels to harness energy from sunlight and turn it into electricity. You could also attach a wind turbine above deck or tow behind another vessel that has an alternator attached for power when needed; these are just some of the many options available.

Problems Encountered When Deep Cycle Battery Won't Charge

It's possible that your charger may have failed. Try a different battery if you can, or make sure the charger is compatible with your type of battery (AGM).

If it seems like an old model, consider replacing it as soon as to maintain peak performance and prolonging its life for many years into the future!


Remember the difference between deep cycle batteries with the types of standard batteries. It’s essential to know how these batteries work and what factors can lead them to fail or prevent their maximum potential in the long run.

We hope the guides and tools provided in this article keep your deep cycle battery perform at its best.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.