What Size Solar Panel To Charge Deep Cycle Battery?

What Size Solar Panel To Charge Deep Cycle Battery?

Off-the-grid living is still a difficult feat, but it is becoming more and more reasonable by the day. Because of new trends and technology, a self-sufficient lifestyle is becoming more attainable for everyday people.

If you want to live off the grid, you will likely need deep cycle batteries and charge them with solar panels. However, if you are a newbie at off-grid living, knowing how many solar panels you need and what deep cycle batteries actually entail can be tough.

To learn more about powering batteries with solar panels, read on. This article provides a comprehensive guide to how these batteries work, how you can charge deep cycle batteries with solar panels, performing energy usage calculations, and more.

Let’s get started.

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How do deep cycle batteries work?

The first step to understanding how to power deep cycle batteries with solar panels is to comprehend them and understand how they work. If you don’t understand this, you won’t understand the rest!

When you first glance at one of these batteries, it probably will look just like a standard automotive battery. However, despite the similarities, these batteries are wildly different and only similar in appearance.

The biggest difference between these two batteries is that deep cycle batteries are designed to handle rapid-paced charging and discharge due to solar power.

In comparison, car batteries only provide quick bursts of power to get the engine running. Very different in practice!

In other words, deep cycle batteries not only start the vehicle but also act as a power bank that can power up other electronics. At the same time, they can be charged via solar panels.

More so, you can use nearly 80% of the battery’s capacity without any severe damage. As a result, deep cycle batteries are best for your solar systems during off-grid living.

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Can you use a solar panel to charge a deep cycle battery?

Because a battery can help you go off the grid, it’s no shock that you can use solar panels to charge your battery. However, charging your battery with solar panels isn’t as easy as it sounds.

You can’t just hook the battery up to the solar panels and expect it to work. You need multiple parts, such as a charge controller and power inverter.

Plus, you will need cables and connectors to connect all of the parts.

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Alternatives to be aware of

Because charging up your deep cycle battery with a solar panel requires many parts, many new users prefer buying a starter kit instead.

Starter kits come with all the necessary parts, taking away the hassle of finding appropriate parts. Starter kits are not necessary if you don’t want them, though.

Another alternative is solar power generators. Generators come with all the parts already included.

Much like the kits, many newbies like generators for their convenience and ease of use.

It is up to you to decide which system is best based on your skills, budget, and requirements.

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What size solar panel do I need to charge my deep cycle battery?

Technically speaking, any sized solar panel can charge a battery. The question is how quickly the solar panel can do so.

Because the battery will be discharging a lot of energy, you want to get as high of a capacity as possible.

Unfortunately, there is no easy answer to what size solar panel you should get. Your individual usage and requirements are most important in this discussion, and we don’t know those factors.

You will need to do a few calculations to determine what size solar panel you need to charge your deep cycle battery.

This is the only way to ensure that your battery is charged in an efficient and reasonable amount of time based on your energy usage and production.

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How to calculate your solar requirements

There are multiple factors to account for whenever you are determining your solar requirements. Here are some crucial calculations you need to know:


The first solar power calculations perform include amp-hours. Amp-hours measure how much energy can be stored at once.

Your battery’s capacity is described in AH or amp-hour. For this number to mean anything to you, you have to change it to watt-hours instead.

Multiply the amp-hours by the battery’s voltage to determine its watt-hours. Below is the formula you should use:

Power = Battery Capacity (Amp Hours) x Voltage

For example, let’s assume for the sake of this example that it has a battery capacity of 2 hours and a voltage of 12. Multiply 2 by 12, and you learn the watt-hours is 24.

Energy usage

Next, you need to think about how much energy your devices and appliance will use. The last thing you want is to use up more power than you can produce or store.

You will need to multiply the power of each appliance by the estimated hours of use per day to produce power consumption. Here is the formula for calculating energy usage for each appliance:

Power Consumption = Power (Watts) x How Many Hours A Day It Is Used

For example, assume the coffee maker requires 5 watts, but you only use it for 1 hour a day. The power consumption is 5 with these numbers.

You will need to perform these calculations on all appliances that will plug into the battery. Then, add up the power consumption for each appliance to get an overall picture of your total energy usage.

Total Power Consumption = Power Consumption of Appliance 1 + Power Consumption of Appliance 2 + etc.

So, if you only power up the coffee maker and pencil sharpener with the battery, add their power consumption up. For example, if the coffee makers are 5 and the pencil sharpeners is 2, the total power consumption needed is 7.

Energy generation

The last thing you need to do is figure out exactly how much your panels can generate. Because solar panels can only harvest energy during the sunlight, this is a crucial calculation.

To find out the amount of energy your solar panel can generate, multiply the solar panel power rating by the exposure time. As a result, the panel’s power rating will be expressed in watts. Here’s the formula:

Energy Generated = Panel Power Rating (Watts) x Amount of Exposure

This calculation may be difficult to perform because you can’t give an exact estimate for the exposure time. Your location, temperature, and weather will affect the energy generated and change the outcome day by day.

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How many watts are required to charge my battery?

So, we explained some of the most vital computations you need to perform above, but you still may be confused about the wattage required to charge your battery.

Unfortunately, doing the above computations is the easy part.

Whereas using a formula to figure out energy and production predictions is easy, the exact wattage needed depends on various moving factors.

For example, the type of grid system you select, voltage, exposure time, battery capacity, and solar panel’s specification all impact the wattage needed.

To put it another way, there are too many moving parts to provide any simple computation or answer. Moreover, since some of the factors change by the day, if not the hour, the computations become even less clear and definite.

The best thing you can do is calculate how long it will take to charge the battery with solar energy. Unfortunately, this computation will not give you an exact answer, and it takes several steps to perform.

You will need to compare this amount to your estimated energy usage and production. That way, you have a general picture of what’s needed to keep your battery afloat.

Let’s take it one step at a time.

Step 1: Determine ampere per hour (AH) rating

Find the ampere per hour rating by dividing the solar panel’s power generation by voltage.

Ampere Per Hour Rating = Power Generation (Watts) / Voltage

Remember, you can find the formula for predicting power generation above. The voltage should be provided, such as a 12v battery or 12 volts.

Step 2: Find the average charge time.

Now, find the charge time by dividing the battery capacity by the results from step one.

Average Charge Time = Battery Capacity / Result From Step One

The battery capacity should be listed on the package or battery in Amp Hours. For example, it may say 100AH battery or 200AH battery.

Step 3: Add 10%

Finally, you need to add 10% of charge time to the number calculated from step two. This step gives you a little extra wiggle room to ensure your battery is fully charged.

Final Results = Average Charge Time (from step two) + 10% of Average Charge Time

You will need to calculate 10% of charge time. Do this by multiplying the charge time by 0.10. Then, add the results to the charge time of step two.

This step may make more sense with an example. Say you find that the charge time from step 2 is 40 hours. Multiply 40 by 10% (which is equal to 0.10) to get 4. Add together 40 and 4.

Hence, 44 is the final result. These results tell you that it takes 44 hours to charge up your battery completely. Most likely, your battery will charge much faster.

Key takeaways about these calculations

As you can see, calculating your solar usage can be really difficult. Because there are so many moving factors, we cannot give you an exact answer to what solar panel you should get.

Instead, you will need to do the math for yourself based on your own expectations and requirements.

Although this is a bit of a disappointing answer we would imagine, it’s the best answer we can provide. If you are not willing to do the calculations for your battery, we wouldn’t recommend opting for a solar system in the first place.


Can I use a 24v solar panel to charge a 12V deep cycle battery?

Yes. You can use a 20V panel to power up a 12V battery. That being said, A 24V panel is better than a 12V solar panel for the job.

Just because you can use a 24V solar panel does not mean it’s the best option. Go through the calculations above to determine what size solar panel is best based on your energy usage and needs.

How long does it take a 100w solar panel to charge a deep cycle battery?

Generally speaking, it can take between five and eight hours for a 100-watt solar panel to charge a 12V battery completely. Multiple factors will impact the exact battery charging time, such as the voltage and battery capacity.

If you want to know how fast your 100-watt panel will charge batteries, you need to do the math. But, of course, the same goes for any other panel, whether a 200 watt or 300-watt model.

What size solar panel do I need to charge my RV battery?

The size of the solar panel you need to power your RV battery will depend on multiple moving factors. Your exact electricity usage, output, sun exposure, and setup will all affect the size needed.

Go through the calculations described above to find out what panel you need based on your battery requirements.

Is there an alternative to a traditional solar power system?

Solar power generators can act as an alternative to a traditional solar power system. Generators function as a complete solar power station, including a battery, inverter, and charge controller.

Many people select a generator because it comes with all of the needed parts. You don’t have to buy all of the parts separately. Generators can also be charged very quickly and efficiently.

Why type of battery is best?

Lead-acid batteries tend to be the best as a battery bank. Lead-acid is more affordable and functional, which is why lead-acid batteries are the best.

Lead-acid batteries aren’t your only option, but its best for a solar system.

Final Thoughts

At the end of the day, deep cycle batteries are very confusing. Though they seem simple, they are anything but.

To find out what size solar panels you need to charge your deep cycle battery, you must perform many calculations.

If you are having trouble performing the calculations yourself, you can always talk to a professional. Professionals will help perform the calculations for you and walk you through the process.

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