What size charge controller for a 200w solar panel?

By Matthew Joseph Nandirio •  Updated: 12/05/21 •  8 min read

A few decades ago, it was almost unthinkable to power a house with solar panels for the common man. However, nowadays, almost everyone is moving towards renewable sources of energy. In this, solar energy is taking the lead.

That said, it does not mean that it is as easy as just connecting solar panels on your rooftop. For solar panels to function efficiently, they require the support of other devices. In addition to this, they also come with batteries.

With this, you would be able to ensure that you can use the power they generate even when there is no sun. One device that is crucial in the entire setup is a charge controller.

What Size Charge Controller For 200W Solar Panel?

To determine the size of the charge controller for your 200W solar panel, you need to know the amount of current it produces. On average this value can be anywhere between 8 and 12 amperes, provided your panels get good amounts of sunshine. So, your charge controller should be at least 15 amps.

However, you should not just take the rating of your solar panels into account for this. Instead, you should also consider a multiplication factor to ensure safety. On average, this factor is around 1.25. This should ensure that your batteries are safe.

You can also use the formula to obtain the number of amps if you already know the watts and the voltage. For example, if a 200w panel has 25 V, which is the common voltage, you have to divide 200 by 12. So, you would get 8 amperes. And you should use a charge controller that is enough for this value.

What Is A Charge Controller For Solar Panel?

Before you can fully appreciate the use of a charge controller, you should first understand what it is. A charge controller is basically an electronic device that stops your batteries from absorbing too much charge. In this way, they play a vital role in preserving the lifespan of the batteries.

So, what exactly happens when you charge a battery too much? Well, the exact sequence of events depends on the kind of battery you have. For example, in a lithium-ion battery, too much charge can affect the stability of the battery.

You can better understand this after knowing what goes on inside a battery. A battery has two electrodes, namely, cathode and anode, and an electrolyte in between. It is with the help of this setup that the battery functions. Each part has its function – primarily, oxidation and reduction.

In a lithium-ion battery, when the battery absorbs too much charge, an oxidation reaction happens in the electrolyte near the cathode. This reaction releases a lot of heat. In addition to this, the gaseous products formed also increase dramatically.

So, you get the picture. A reaction occurs which raises the temperature, and the higher temperature fuels further reaction. Thus, when you charge the battery more than you are supposed to, you end up in this cycle. This raises the pressure inside the battery.

However, that is not all there is to it. If you remember, there is also another electrode, which is the anode. On this side also, you would observe a reaction that increases the temperature of the set-up. Further, this reaction is quite vigorous in nature.

In a lead-acid battery, charging it too much can expose you to harmful chemicals. How? Well, when you charge a lead-acid battery, you also make it emit small concentrations of hydrogen gas. This is not a problem – hydrogen gas also exists in the atmosphere. The issue only starts when the concentration of hydrogen exceeds the optimal amount.

When you allow a lead-acid battery to absorb more charge than necessary, you make it susceptible to release a gas called H2S. If you have ever noticed a strange scent coming from what you know to be a lead-acid battery, it could probably be due to this gas.

H2S can have significant effects on your body. In high amounts, it can even be lethal. Therefore, ensuring that your battery gets only the optimum amount of charge is essential. Here are some types of charge controllers that help you achieve this:

  • Shunt Controllers

These are some of the easiest ones to understand. They work by first understanding how much energy a battery needs. If too much electrical energy goes to the battery, they use a shunt mechanism. They do this by making the current go another way.

To do so, they establish a pathway where the resistance is lower than the path to the battery. Hence, electricity takes the path that counters it less. In this way, these controllers ensure that your battery does not accept more charge than it can handle.

  • Series Controllers

These also have a very straightforward mechanism. They function as a switch does – that is they turn on or off. When too much charge goes to the battery, they open the circuit. So, the charge can no longer flow towards the battery.

For them to function properly, you have to place them between the array of solar panels and your battery. Only then can they break the circuit and protect your battery.

  • PWN Controllers

These are some of the most popular kinds of charge controllers. One reason why they are so popular is that they are able to offer several advantages at a low cost. This makes them suitable for small-scale functions, such as using them in a home.

They monitor the amount of charge in a battery at different stages of its function. They do not cut off the energy flowing to your battery. Instead, they diminish the amount of current flowing. In this way, they ensure that the current does not go above capacity.

How Do I Choose The Right Size Solar Charge Controller?

Now that you know how important charge controllers are, you would want to know how small or big of a controller you can buy. Understanding this will come in handy if you want to expand or reduce your dependence on solar panels.

  1. The size of your charge controller would depend on the power your solar panels produce, in addition to your battery. As a general rule of thumb, more power would imply that you need a bigger controller.
  1. In addition to this, some controllers can manipulate the amount of charge flowing through them. This is not true for shunt or series controllers.
  1. So, for them, you need to ensure that they can handle the maximum amount of electricity that your solar panels produce.

How Many Amps Does A 200 Watt Solar Panel Produce?

The amount of amperes a 200 W solar panel produces, depends on its voltage. It also depends on whether or not you would like to measure DC or AC. This is because solar panels produce only DC.

If you measure the current you receive in your home from these panels, you would get the value of AC. You get this current after it passes through the inverter. Hence, this would not be higher than the value you would get if you directly measure DC. You have to account for losses from the inverter which is about 10%.

That said, the average value of amperes a 200-watt panel produces is around 8. You would be able to get the average value of amperes that your panel produces from the specific details that the engineer gives. It is quite accurate and relatively simple to do.

How Does Amp Size Effect On Selecting A 200w Solar Charge Controller?

Amps directly impact the selection of the charge controller. The charge controller functions to protect your batteries. So, the number of amperes is a very crucial factor. If you choose a charge controller that is too small a size, you run the risk of your equipment burning.

However, that is the worst-case scenario. At best, you would notice that the amount of electricity your panels are generating is getting wasted.  Thus, the amp size should be the deciding factor when selecting your charge controller.

After this, you can also filter by the type of charge controller, depending on the need of your application. For example, some controllers have continuous monitoring that you may or may not need. The cost would also be a factor. You should also remember that the charge controllers will not drain the energy from your batteries.


Hope you understand why a charge controller is essential for your solar panels. In addition to this, you would also be able to estimate the size of your charge controllers. That said, you should also consider other factors like cost and type of controller before you make a purchase.

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