Can a solar charge controller overcharge a battery?

By Matthew Joseph Nandirio •  Updated: 05/02/22 •  7 min read

A solar panel’s main purpose is to charge a solar battery. It, therefore, does not concern itself with the process of checking if the battery is full or not. A solar panel will continue sending current to the battery so long as the sun is available. 

Sometimes, the battery will overcharge, which might lead to it becoming defective. A charge controller is installed into the solar PV system to prevent this from happening. Charge controllers regulate the amount of current reaching the solar battery. But can they cause a solar battery to overcharge?

The answer is no. A charge controller regulates the amount of current reaching the battery. They also detect when the solar battery is fully charged and stops any current from flowing into the solar battery. In this article, we will discuss the different types of charge controllers. We will also discuss the benefits of installing a charge controller in your solar PV system. Stick around to find out more. 

Can a solar charge controller overcharge a battery?

There are different types of charge controllers, each with different functions. However, they are similar in ensuring the solar battery charging process is done effectively. They collect even the slightest amount of energy and send it to the solar battery. The big question can the charge controller overcharge a solar battery?

Depending on the type of charge controller you are using, your solar battery can either overcharge or not. We have two common types of charge controllers. 

Solar trickle ensures the solar battery gets a solar energy supply even when the sun is not dependable. Suppose you have installed a solar trickle and the sun is hot. Will it stop more current from reaching the solar battery? A trickle will continue sending more current to a solar battery even when fully charged. This might lead to the solar battery overcharging. 

A solar maintainer, on the hand, ensures the solar battery is charging but can stop more current from reaching the solar battery when it is fully charged. 

Do charge controllers prevent overcharging?

Charge controllers are divided into two main types: PWM and MPPT. 

Pulse With Modulation (PWM) balances the voltage and the current between the solar panel and the solar battery. PMW controllers are also known as maintainers. These controllers detect the amount of current being received by the solar battery and match the output. 

When the current is high, they allow more energy to power devices. Once the solar battery is full, they stop any more current from reaching the solar battery. Therefore preventing the solar battery from overcharging. 

On the other hand, maximum PowerPoint Tracking charge controllers detect when the solar energy is high for effective charging. MPPT controllers allow more charge to reach the solar battery even when the sun is unreliable. 

MPPT controllers do not balance the voltage and current of the solar battery. They continue sending more current to the solar battery even when it is full. This could cause the solar battery to overcharge. 

If you want to utilize maximum solar energy and prevent your solar battery from overcharging, you should install a PWM and MPPT charge controller. MPPT will ensure the solar battery is charged efficiently, while PWM will regulate the solar battery’s current.

Can you leave a solar battery charger on all the time?

A solar battery can power a load and charge at the same time. For this reason, you should always leave the solar battery charger on at all times. 

Standard solar batteries have a capacity of 12V and 50a. Once the capacity is reached, the solar battery cannot accommodate more charges. If the solar battery charger keeps sending more current to the solar battery, the solar battery will overcharge. 

A solar battery overcharging is not a good thing. When the solar battery is overcharged, it loses its efficiency. It, therefore, cannot complete its life span. Overcharging can also cause the solar battery to overheat, which can cause a fire. 

If you want to leave your solar battery charger on throughout, you should connect charge controllers to the PV system. 

Charge controllers will regulate the amount of current reaching the solar battery. 

Solar batteries require at least 14V to be fully charged. Charge controllers detect when the solar battery is at 12.8V and starts charging the battery using a technique known as Float charging. They detect when the solar battery is fully charged and stops further flow of current. 

How do you keep a solar panel from overcharging a battery? 

Solar batteries are a deep cycle that accommodates thousands of discharges and recharges. For that reason, a solar charger is always left connected to the solar battery. 

If the charging process is not regulated, a solar battery might overcharge. Overcharging can result in our solar battery overheating, causing a fire. 

You can use several techniques to prevent your solar battery from overcharging. 

Connecting load in between the battery and the solar panel 

You can use an inverter for this purpose. When an inverter can power an appliance and charge the solar battery simultaneously.

This can only work if the solar panel produces a large current and the load output does not overpower your solar panel. After the load is powered, the excess energy is used to charge the solar battery. 

Using solar charge controllers

A charge controller’s main purpose is to regulate a solar battery charging process. They ensure the solar battery is effectively charged even when the sun is not efficient. That is not their only role in a solar battery. They detect when the battery is fully charged and stop further current flow. 

Charge controllers are your best chance to prevent your solar battery from overcharging. However, they do not guarantee your solar battery 100% protection. Controllers are artificial and are prone to becoming defective. To ensure they do their work efficiently, you should take further steps.

  • Check the state of the charge controllers: Since charge controllers can become defective anytime, you should check if they are in the right condition. Charge controllers have sound and light signals that tell the total voltage in your solar battery. 

If the voltage of the solar battery indicates it is fully charged and no signal is sent, then your charge controller is faulty. 

  • Learn your solar battery charging process: if your solar battery takes 5hours to fully charged when drained, check the solar battery after 5 hours. This will be helpful if you do not have s charge controller connected to your solar PV system. 

You can do this by calculating your solar battery’s wattage and comparing it with that of your solar panel. 

  • Observe the weather: more current is sent to the solar battery when the sun is hot. On the other hand, when the sun is insufficient, the solar battery takes longer to charge. 

You can use a multimeter to measure the charge available in a solar battery on hot days. This way, you can tell when the solar battery is almost charged. 


Although solar energy is clean and renewable, it can cause some serious damage to your home. An example is when a solar battery overcharges. 

Overcharging might result in the battery overheating, which can cause a fire. To prevent this from happening, connecting solar charge controllers to your solar PV system is advisable. Our guide above gives you the advantages of installing charge controllers and other ways you can use to protect your solar battery from overcharging.

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