How Long Does It Take to Charge a Marine Deep Cycle Battery? 

You need an efficient battery to provide consistent voltage to your boat. Not only does it make your journey smoother, but it also keeps you from running out of power while on water. 

Deep cycle batteries provide a steady voltage for a long time and are an excellent choice for powering your boat motor. 

However, to make the most out of these batteries, you must charge them correctly, and knowing the timings is crucial to ensure that. 

The charging times of the marine battery vary depending on the charge left in the battery, amp-hours, and age. 

An insight into numerous factors affecting the charging times will help you understand further. 

Why Is It Important to Charge the Marine Deep Cycle Battery Properly? 

Gadgets need proper maintenance to enjoy their boosted performance. The case isn’t any different for deep cycle batteries. Correctly charging them maximizes their life expectancy and ensures their optimal performance. 

Lead-acid batteries, for instance, get damaged due to overcharging. Besides, using the batteries past 50% also affects their performance. 

How Long Does It Take to Charge a Marine Deep Cycle Battery?

However, such downsides do not exist for marine lithium batteries. You can use them below 50% charge and do not need to charge them instantly after utilizing the charge. 

This comes in handy if you go boating occasionally. It keeps you from the trouble of immediately charging the battery after a tiring day.

Nonetheless, you must follow the best charging practices even if you use lithium-ion batteries (more on the topic below). 

Battery Charging Cycles

To understand how energy distributes in the battery, you’d need to look at the different charging stages. These include the following: 

  • The bulk stage. It is the first stage of the charging procedure. Here, the battery detects the maximum voltage, and the energy is distributed throughout the battery. The charger maintains a constant voltage during the process. 
  • The absorption stage. The voltage lowers when the charging process moves from bulk to the absorption stage. 
  • The float charge stage. The decreasing voltage is a plus as it signifies the battery’s internal resistance is increasing. When the battery fully receives the power, and its resistance hits the maximum, the voltage is lowered further. This is called the float charge stage, and here’s when the trickle charging process begins. 

The trickle process, also called maintenance charge, ensures your battery’s and motor’s safety. The specialized procedure only outputs the amount of energy needed by the battery. 

As such, it provides energy when the battery begins to lose power, keeping the battery from using energy more than the required amount. Consequently, the process prevents your battery from losing too much energy when discharging. 

Marine Deep Cycle Battery Charging Time

The battery charging time is the time the charger takes to transmit energy to the battery’s active cells, re-energizing it. 

The process also ensures maintaining the temperature at safe levels. For instance, the battery shouldn’t get too hot. Otherwise, it will deteriorate the battery’s health. 

Because there is no set time for the battery charging, we need a deeper dive to understand the timing for different batteries. Typically, the battery charging time depends on two factors: 

  • The ampere-hour rating of the charger
  • The ampere-hours capacity a deep cycle battery stores 

You can use a simple formula to estimate your battery’s charging time. Divide the battery capacity by the Ah rating of the charger. 

Say the capacity rating of your deep cycle battery is 200 Ah, and its current charge is 50%. You’d need around 100 Ah to fully charge it. 

If you own a 10 Ah charger that outputs 10 amperes per hour, you’d need 10 hours to charge your battery fully. 

However, not everyone can afford the luxury of keeping the battery on charging overnight. Therefore, it’s better to go with a 20 Ah charger, cutting your initial charging time to 5 hours. 

Further, if you buy fast chargers that output 50 amperes per hour, you’ll reduce this timing to 2 hours. 

On a side note, experts do not suggest using fast chargers. Slow chargers – those with less amp hour ratings – charge your battery slowly, but they won’t overcharge it, which is highly likely using fast chargers. 

A Quick Look Into Battery Charging Timings 

How long it takes to charge a battery depends on the ampere-hours and the battery capacity. Some examples will give you a deeper understanding. 

  • Charging a 12V marine battery. A 12V battery with a 105-ampere hour rating can take around 10 hours to charge fully. 
  • Charging a marine battery at 2 amps. A completely discharged deep cycle battery takes up to 50 hours to fully charge. Nonetheless, it may differ depending on your battery’s size. If you own a 12V charging with a 100 Ah rating and wish to charge 2amps every day, it’ll take more than a week to charge it fully. 
  • Charging a battery at 4 amps will take 25 hours to charge the required 100 Ah of the battery. 
  • 10 amps. Charging a 150 Ah battery at 10 amps will take around 15 hours to be fully charged. 
  • 15 amps. It will take up to 7 hours to charge the required 100 Ah of the battery when charging at this rate. 
  • 40 amps. You might want to charge at this rate due to an emergency. It’ll take around 2 hours. However, charging at a faster speed can be dangerous for your battery’s health. In fact, it may explode the battery in more severe cases. 

Things to Consider When Charging a Marine Deep Cycle Battery

There’s no secret sauce to charging your marine battery, but you need to keep a few things in mind to charge it safely – and extend its life expectancy. 

Charger Type 

You need to purchase a quality charger built specifically for your marine battery, and there are no two ways about it. For instance, a lithium charger will optimally charge a lithium battery. 

A few people use batteries and chargers interchangeably. While this hack works, pros do not recommend it. For instance, your charger may reach a voltage your battery fails to handle. 

Consequently, you might deteriorate your battery or see an error. Further, the battery may fail to charge in the worst-case scenario.

A correct charger type will charge your battery faster. For example, lithium batteries charge faster than other battery types. However, you’d need to use the right charger, to begin with. 

But the question is, how to ensure you’re buying the correct charger? 

You can read the charger’s description; it specifies the batteries it works with. 

Lastly, you can pick from onboard or portable chargers. 

  • Portable chargers are an excellent option for boaters who wish to enjoy greater convenience when charging their batteries. They can carry these chargers even on a small boat and charge their batteries on the go. 
  • Onboard chargers. They are cost-effective, lightweight chargers and typically come with a five feet long cable. A few also show you the charging status through LED lights. 

Right Voltage 

After discovering the right charger, you must choose the right amps and voltage. For instance, a 10V charger is compatible with a 10V battery. You’ll also have the option to pick from a 10V battery category – that is, you can choose from varying charge currents. 

Further, you’d need to check your battery’s Ah rating to select the right amps. For example, the Ah rating shouldn’t exceed your battery’s ampere-hour rating. Otherwise, your battery will deplete and might fail to function.  

Optimal Temperatures 

Maintaining an ideal temperature is crucial to ensure your battery charges efficiently. Temperatures too low and too high can negatively impact the battery’s performance. Even more, your battery might not charge at all. 

If you live in freezing temperatures, you can go for a charger equipped with a heater. 

Steps to Charge the Battery 

Now that you have the right charger with optimal voltage, it’s time to charge your deep cycle battery. Here’s how to go about it: 

  • Thoroughly clean the battery terminals. If you spot rust, we recommend using sandpaper to get rid of the corrosion. Following this, clean the terminals with an alcoholic wipe, and you’re good to go. 
  • Connect the positive cable to the red terminal and the negative one to the black side. 
  • Now insert the charger and turn on the switch. 
  • If you’re using a smart charger, lucky for you. You can adjust the settings to set and forget. The charger will automatically stop charging your battery when it’s complete. The ionic lithium batteries make charging even easier because they feature Bluetooth. 
  • Once the battery is fully charged, disconnect the charger by unplugging it. 
  • That’s it! You have successfully charged your deep cycle battery

While choosing a suitable charger is crucial to ensure the battery’s optimal performance, you must also be cautious about the battery timings. 

If you do not own a smart charger, you must always remain alert. Once the battery charges, unplug the charger immediately. Otherwise, you’ll overcharge the battery and damage it eventually. 

Do You Need a Special Charger to Charge a Deep Cycle Battery? 

Because deep cycle batteries cannot tackle the excessive heat of standard chargers, you need a charger designed specifically for a deep cycle battery. It will charge your marine battery cycle correctly and boost its lifespan. 

Do Deep Cycle Batteries Get Overcharged? 

The battery will easily overcharge if you forget to unplug the charger after charging your battery. This will overheat the battery and might corrode it in the worst-case scenario. Gradually, your battery’s life drastically decreases, and so does its performance. 

Therefore, it is better to purchase an automatic deep cycle charger. It detects the battery charge and stops it immediately, switching to the maintenance mode. 

Keeping the batteries from overcharging isn’t the only perk of automatic chargers. They also come in handy when you do not want to use the batteries during the off-season. 

These chargers constantly charge your batteries, keeping them from going bad. As such, they contribute to your battery’s lifespan and performance. 

Is It Important to Charge a Newly Purchased Deep Cycle Battery? 

Newly bought deep cycle batteries are fully charged. However, it doesn’t hurt to check them before use. If you spot a slightly low battery, you can always charge it. 

Besides, note that your new battery will take a few charging cycles to hit its maximum potential. You can speed up this process by discharging the battery before recharging it.

Is It OK to Leave a Battery Charger On? 

It’s ok to leave a battery charging on so long as your battery is drained. However, you must keep the charging timing in mind to disconnect it when needed. 

If your battery is charged, you should not leave the charger plugged in for a long time. It’ll reduce your battery’s performance and damage its compartments. 

When to Charge a Deep Cycle Battery? 

How often you should charge a deep cycle battery depends on your usage. You need to charge it regularly if you use your boat intensively. However, charging it twice a week will do if you only use it frequently and for shorter periods. 

Note if you’re using it only occasionally, you should reduce the charging frequency to at least a month – not less. Otherwise, it will run empty and drain. 

When to Stop Charging a Deep Cycle Battery? 

You should immediately unplug your battery’s charger when the light indicates that the battery is charged fully. Although it doesn’t hurt charging a battery for a few additional minutes, it is better to remove the charger. 

However, pros recommend following the best practices to ensure the battery’s efficient performance. Therefore, removing the charger when the charging reaches its required point is better. 

Wrap Up 

A deep cycle battery provides a steady charge to your boat and ensures a safe journey. However, you need to understand the charging considerations to avoid overcharging your battery. 

The charging time of the battery varies, and you need to check the voltage and ampere-hours to determine yours. 

Our guide discussed the formula to calculate the battery charging timing, the steps to power the battery, and a few commonly asked questions. 

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