How Many Watt Solar Panel to Charge Deep Cycle Battery?

Many find it convenient to go off-grid completely. However, regardless of your reasons, solar is required for your energy needs. This self-sufficient energy will not have you dependent on public utilities as you can tap from the gift of nature to provide your needs and yet not harm the environment while at it.

After tapping solar energy from the sun, there is a need to store this energy by using batteries as they are known to be a stable and dependable source of power for the home. However, determining how many watt solar panels to charge deep cycle batteries can be confounding, not with all the technicalities that seem to be involved. Do you wish to set up your rig for your solar panel but don’t know the setup size that will be needed?

Your questions will be answered as in this article. We will educate you on all you need to know about charging your deep cycle battery using solar energy.

Table of Contents

Definition of Deep Cycle Battery

A deep cycle battery is a lead-acid battery whose capacity is regularly meant to be discharged; the discharge can occur between 45% and 74% of the capacity, but this is dependent on several factors such as the brand of the product and its design. However, the best lifespan will keep your battery at a constant 45% discharge and is constantly used in off-grid situations.

This is not all; the deep cycle batteries can also be used in cars, boats, and RVs as they are designed to recharge and discharge over a hundred times over.

Calculating Solar Panel Specifications

In order to know how best to charge your battery with the use of a solar panel, there is a need to calculate what your solar power requires. This will enable you to determine how many watt solar panels to charge a deep cycle battery. In this, there are three factors to consider to ensure your result is accurate. They include:

1. How Much Energy Your Battery Can Save?

Every battery has a maximum storage capacity that should be considered if you are in need of an adequate and dependable power supply. Purchasing a battery with the ability to store more energy is of paramount importance as this way, you are assured of your system’s efficiency and dependability.

The capacity of a battery is measured in amp-hours. This can be done by multiplying the voltage of the battery with the amp hours on your battery and can be calculated using the formula below:

Power (watts) = Capacity of battery (ah) x Voltage of battery

Example 1:

If your battery has a voltage of 12 volts and a capacity of 20 amp-hours, then it follows that the power in watts hours is the voltage of the battery multiplied by the capacity of the battery.

Power=12 x 20

Power =240

Example 2:

A battery capacity of 350ah can continuously supply 35amps for 10 hours straight of 17.5 amps for a period of 20 hours.

On purchasing some appliances and devices, the amount will be clearly stated on the product, so you need not convert anymore to determine how much energy that device can store. However, note that this information relayed so far will be needed to discover what will be required from your solar panel.

2. Amount of Energy Consumed By Appliances over Time

Before you can determine the amount of energy you will need, there is a need to ensure your solar panel can handle your home’s electrical grid. One of the ways of doing this is by looking at how much power your home devices consume over a certain period. This analysis will give you a rough estimate of how much energy is needed to keep your home running at all times.

The standard unit of measurement for power is wattage, so you will need to get the value of energy consumed by your appliances over a particular time (this is usually measured in WH), then calculate the power consumed using the formula below:

Rate of Power consumed over time (WH) = power (watts) x Hours of Use (Hr)


WH = 5 X 20

WH = 100 WH

3. How much energy does your solar panel generate?

In the end, there is a need to consider how much energy your solar panel generates over time to determine how much energy is generated. Solar panel’s rating is usually calculated in watts. However, to determine how much energy is delivered to your battery from the solar panel, you will need to multiply the power generation rating on the solar panel by the number of hours it is exposed to the sun.

To do that, use the formula below:

Amount of energy generated over a period = solar panel rating (watts) x amount of time exposed to the sun (hr)


Suppose your solar panel has a rating of 10 watts and it is exposed to the sun for about 10 hours. In that case, it follows that the amount of energy generated over the period is the watt rating multiplied by the exposure time.

Energy generated over a period = 10 x 10

This gives 100 WH. This is, therefore, the energy generated by your solar panel, which is used to power your deep cycle battery.

If these factors and aspects are considered before installing a solar panel system, you will know what to purchase to ensure you have a reliable system. Yes, an off-grid system provides all the power needed to run your home every day. However, to have a highly efficient and reliable system, there is a need to work on all possible factors before going ahead to set up your solar panel. With all these, it’s now possible to know how many watt solar panels charge a deep cycle battery.


This converts your storage battery to 240 volts AC needed to run your home, and unless you only run 12volt DC devices, you will need an inverter to supply your AC.

Two types of inverters exist, and they include

Pure Sine wave Inverter

This is similar to the power generated from the electric supply. It is clean and can be used to power even sensitive devices.

Modified Sine wave inverter

This is said to be a dirty power, but this is not necessarily true as there are more improved and better versions than what we used to have in the past. This inverter can be used for appliances that are not so sensitive. Examples include fridges, pumps, and cookers. However, you may need to be careful while using it for sensitive devices like laptops and TVs or, better still, avoid using it for that purpose entirely.

Charge Regulators

Solar panels of 30watts and above should have a charge regulator or controller. This is vital as it protects your batteries from overcharging or over-discharging; instead, it supplies only the amount needed to enable your batteries to last longer. With a charge controller or regulator, your battery is at risk of being damaged.

What Every Solar Panel Should Use?

It’s important to note that solar panels are about numbers (power needed versus power generated). Before you even think about purchasing a solar panel, you should know the name of amp-hours or watts that can be generated over time. This can be estimated in days or hours.

Since we have 24 hours in a day, it is advisable to use that as a benchmark to get an accurate result. Start by determining the aggregate electricity utilized in that day and age. During this time, try to figure out the amount of direct sunlight the solar panel was exposed to on that day and age and then think of an approximate sum of watts hours required.

We observe four long periods of usable daylight during winter and six long stretches of usable daylight during summer on an average day. Note that there are exceptions to these estimates, including factors such as shades, mists, angle of the panel, and so on. Having gotten how to calculate the capacity of your solar panel and battery, then use a solar calculator.

You can use this tool to check:

Using an excellent solar charger will also ensure you get the best service available. If you want a reliable and efficient battery that will not leave you with a power shortage, you should use the best solar chargers.


Generating and storing solar energy on your deep cycle battery is relatively easy and not as difficult as perceived. All you need is a few clean devices, and just like that, you can have safe, clean power to run your home. This article has been able to answer how many watt solar panels charge a deep cycle battery. It is an efficient and reliable system and can be installed anywhere in the home for excellent service.

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