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How Many Batteries Do I Need for a 200 Watt Solar Panel?

By SSK Admin November 03, 2021

How Many Batteries Do I Need For A 200 Watt Solar Panel

Solar panels are a great way to avoid rising electricity prices, combat unplanned power outages, or travel off-grid in an RV. 

To get the absolute most out of them, we would recommend using them in combination with the right type of batteries. 

But what is “the right type of battery”, and how many of them do you need? 

It is often overwhelming to know exactly what you need when you’re putting together your first solar array. 

That is why we are here to give you a breakdown of how many batteries you will need for a 200-watt 12V solar panel, what type of batteries are best, and what other devices you might need for your solar array.

Batteries for 200 Watt Solar Panels

Sizing Your Battery Bank for Your 200 Watt Solar Panel Array 

How Many Batteries Do I Need For A 200 Watt Solar Panel

Calculating the size of the batteries you need, as well as how many you need, is quite a lengthy process, but we are going to take you through it step by step. 

It is important to take note that in terms of battery size, bigger isn’t always better. 

Yes, a bigger battery might be able to store more energy, but it will also take much longer to fully charge, considering that a 200-watt solar panel isn’t that big, either. 

Let's get going with the calculations

Daily Energy Use

The first step we need to consider is calculating how much electricity you need to produce for all of your appliances to run, and how long you want them to run per day.

To get the watt-hours you need per day, multiply the watts of each appliance by how long you want them to run per day.

For a very simplified example, if you have two LED lights that need 5 watts of electricity to function and that you want to run for 7 hours, a fan that draws 45 watts that needs to run for 5 hours, and a cell phone charger that draws 4 watts need to run for 2 hours, your watt-hours calculation will be as follows:

5 x 2 x 7 + 45 x 5 + 4 x 2 = 303 watt-hours per day.

Since devices don’t always work as effectively as they claim to, we multiply the watt-hours by 1.5 just to account for any extra power that they might draw. 

This will make our watt hours 454.5 Wh.

Amp Hours

The following step is to convert our watt-hours into amp-hours in order to calculate the battery size. 

To do this, divide the watt-hours by the voltage. If you have chosen a 12 v system, the equation would be 454.5/12 = 37.87 amp-hours.

Since batteries often only store about 50% of usable storage, we want to multiply that amount by 2.

This would equate to 37.87 x 2 = 75.75 Ah.

Meaning that you would need at least a 75.75 Ah 12 V battery to be able to keep up with your daily electrical needs.

To be safe, we would recommend a 100 Ah 12 V to meet your daily needs.

However, it is important to keep in mind that the above example is very simplified, and just an example to show you how to work out what size battery you will need specifically for your solar array.

In general, a couple will use approximately 200 amps of electricity per day. So in this case it is recommended to get a 225 Ah 12 V battery.

The important thing is that your battery needs to be sized according to your specific needs.

Amount of Batteries Needed for Your 200 Watt Solar Panel Array 

Amount of Batteries Needed for Your 200 Watt Solar Panel Array

After working out your solar electricity needs in terms of amp-hours, you can now figure out how many batteries you will need. 

If we use the above example’s 225 Ah 12 V battery as our battery of choice going forward, you would think that one battery would be enough to keep your system running.

However, it is important to remember that devices aren’t always efficient, and other devices such as charge controllers and inverters also draw electricity, so in this case, it would be safer to have two batteries. 

Because of all the other factors that need to be considered first, you can’t accurately say you will need a set amount of batteries for every 200-watt solar array.

Battery number is very specific to your solar system and needs to be calculated according to your setup.

Why Do Solar Panels Need Batteries?

After finding out the answer to the question “how much do 200-watt solar panels cost?”, you might be reluctant to invest in all the other gadgets that come with it, too.

But, we can assure you that having batteries with your solar panel is so much more beneficial, and worth the initial splurge.

Without batteries, you aren’t able to store any energy. This means that on an overcast day, your solar panels won’t generate electricity to power your appliances.

Batteries store energy from your solar panels so that you can power your appliances at night and on days when there is no sunlight.

Without them, you will very likely be left in the dark, unable to live off-grid, and have no emergency power backup.

Battery Type May Affect the Number of Solar Panels You Need

If we compare a 100 vs 200-watt solar panel, we know that a 100-watt solar panel produces roughly 5-6 amps per hour. In a 200 watt solar panel, this will most likely translate to 10-12 amps per hour.

We can estimate that in a day there will generally be about 6 hours of decent sunlight to power your solar panel. This means that a 200-watt solar panel will likely produce 60-70 amp-hours per day.

If we use the above example’s 225 Ah 12 V battery as our battery of choice going forward, one 200-watt solar panel will not be enough to fully charge this battery in one day, especially if you decide to go with two batteries.

In order to charge one battery, you would need at least three 200 watt solar panels to do the job.

Additional Devices Needed to Go with Batteries

When purchasing a battery, you need to consider all the additional gadgets and devices that need to be bought with it. These are important as they also determine how much electricity you expend, and affect the battery size and/or amount needed.

The most important additional elements are a charge controller, inverter, and gauge wire. 

Charge Controller

How many batteries can a 200 watt solar panel charge

A charge controller prevents your battery from overcharging. There are two types of charge controllers available, a Pulse Width Modulation (PWM) charge controller and a Maximum Power Point Tracking (MPPT) charge controller.

A PWM can lead to a lot more loss of solar energy, and could potentially influence your battery size and the amount that you will need. 

Inverter

Inverters work to convert direct current (DC) into alternating current (AC) so that it can be used by your appliances. 

This makes it an important element to have, but defective inverters can also lead to loss of energy. 

This is something that needs to try and be avoided, but also to take into consideration in terms of your battery size. 

Gauge Wire

In terms of your solar array, your 200-watt solar panel wire size, or wire gauge, is very important. 

If your wire gauge is too small and creates a lot of resistance, this can lead to a lot of power being lost from your system, which can affect how much power you need to generate, and the battery number and size that you need to capture the necessary electricity. 

Why the Wiring of Your Solar Array is Important 

How you wire and string the components of your solar array is very important. It affects the voltage and the current across the panels, which in essence affects the power output of the system. 

To make sure that the wiring is done correctly, that the power that needs to be stored isn't affected, and that your system is running at its maximum capacity, we would recommend consulting a 200-watt solar panel wiring diagram beforehand so that you can assure that it is done correctly and that your system functions as efficiently as possible. 

Final Thoughts

As we mentioned earlier, saying how many batteries you will need for a 200-watt solar panel is not a set thing. 

It is based on your solar array and needs to be very specific and individualized. 

So, the best way to get the answer for your particular solar array would be to follow the steps we provided above, and calculate what would suit you best.

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