Why does my solar battery drain so fast?

Solar batteries can drain faster than expected, and it’s a problem that many solar system owners face. This article provides a comprehensive guide to understanding why your solar battery might be draining quickly and offers maintenance tips to extend its lifespan. The average lifespan of a standard solar battery is up to 10 years, so if it stops working efficiently within a few months, you have a significant issue.

Common reasons for rapid battery drainage include faulty solar inverters, inadequate sun exposure, overheating, and using batteries of different voltages in the same bank. These factors can significantly affect the performance and longevity of your solar battery. A battery that sits unused for more than eight months is also likely to drain faster.

Proper maintenance is crucial for battery longevity. For instance, using high-quality batteries and ensuring they are fully charged can make a difference. If your battery is not holding charge as expected, it could be due to a faulty sensor, low-quality components, or a defective charge controller.

Investing in high-quality solar panels and batteries can significantly extend the time your battery holds its charge, sometimes up to 5 to 7 days. Therefore, understanding the various factors that influence battery drainage can help you make informed decisions and extend the life of your solar battery.

Why does my solar battery drain so fast

The sad fact is that even the best solar battery will die one day. That does not mean a new solar battery should stop working efficiently. The lifespan of a standard battery is up to 10 years. So if after three months the solar battery stops working, you have a huge problem.

There are a couple of reasons why your solar battery might be draining faster than it should. Apart from a damaged battery, other reasons that might be causing your solar battery to drain include;

  • A faulty solar sensor
  • Not enough exposure to the sun
  • The battery is overheating
  • Using an uncharged battery
  • Using batteries that are not of the same voltage in the same bank
  • A battery sitting more than eight months without being used
  • When you use deep cycle batteries to start the engine

Stick around to find out how the reasons listed above affect your solar battery

Why are my solar batteries not holding power?

Proper maintenance of your solar components will go a little further in protecting the life span of your solar battery. If you happen to notice that your battery is not holding charge as expected, one of these things might have happened.

1. A faulty sensor

A sensor is an essential part of any solar lighting system. It senses when it gets dark and light up the solar and switches off when the daylight emerges.

If a solar sensor is defective, it might be hard to detect when daylight comes. The consequence is that the battery will not hold any charge, which eventually drains the battery. 

2. Low-quality batteries

Although solar batteries will die eventually, do not rush buying a cheap solar lighting system. The chances are that a cheap solar will come with a battery that dies after a few hours of lighting up your space.

Components of a cheap solar lighting system are prone to becoming defective easily. When a solar panel is damaged, it cannot harvest enough sunlight energy.

3. The battery is overheating

A charge controller regulates the amount of voltage your solar battery can handle. If the solar charge controller is defective, it cannot protect the battery from overcharging. 

When the battery charges with high amps, it will charge faster, and in return, it dies twice as fast.

4. Using an uncharged battery

One huge mistake you can make is using a not fully charged battery. Sometimes there is not enough sunlight to charge the solar battery. Using an uncharged battery for a long time causes permanent damage to the battery. 

5. Using batteries that are not of the same voltage in the same bank

Using batteries with different voltage means in the battery components increases the chances of your battery dying.

6. A battery sitting more than eight months without being used

Batteries discharge naturally. When a battery stays up to eight months without being in use, chances are that it is already draining the charge on its own. It will, therefore, not last long. 

Batteries that are plug in use immediately after manufacturing have high chance of lasting longer. 

7. When you use deep-cycle batteries to start  an engine

The purpose of deep-cycle batteries is helping to maintain the longevity of your batteries. Using deep-cycle batteries to start up powerful electronics will make them die slowly and eventually fail completely.

8. Storing an uncharged battery

If you plan to store your solar battery for a while, make sure the battery has maximum charge. You should also make sure the temperature of the place you are storing is not above 95°C. High temperature causes an internal discharge leading to sulfation.

How long will a solar battery hold its charge?

Investing in a high-quality solar panel is a game-changing move that you should consider. Solar panels harvest the excess energy released by the sun. The energy is then stored in the battery and used to power our residences. 

One significant merit of solar lights is that you can enjoy up to 30 years without ever needing to buy new components. In fact, most brands promise you may use your solar batteries without ever needing to buy new components. 

When the battery is in the proper condition, and all the other factors are balanced, it can last up to 5 days without dying. Some batteries last for seven days of power. 

Several reasons like the type of battery and usage also affect the duration your battery will hold power. We will briefly discuss how these reasons influence the longevity of your battery.

Proper charging  and maintenance

Maintenance practices are a crucial part of a battery life span. Proper charging of the solar lighting system will determine how long your battery lasts. 

Ensure you know the amount of time your solar lights take to charge. To ensure the battery is charging perfectly;

  • Clean the solar panel regularly
  • Install the solar panel on an open space
  • Connect the solar light’s components correctly

Ensure you store the battery with full charge if you are not using the battery for long.  

The usage of the battery

After using a battery for a long time, the longevity will deteriorate. For example, after using a solar light for ten years, it might start dying faster. 

If you use your solar lights to light up your residence every day, it might end up getting the battery drained.

 On rare occasions, the weather affects how long the battery lasts. During the winter, the battery cannot fully charge. In return, your battery cannot light up properly.

Should you unplug solar panels at night? 

A solar battery charges up during the day when sunlight is and lights up your residence at night. So during the night, the battery is not charging. The battery, therefore, drains at night. However, this does not call for you to switch off the solar panel at night. 

Install the solar panel well to prevent them from draining power from a battery. You should also install a solar charge controller to protect the battery from overcharging.

How to know if the solar battery is fully charged?

Battery charging improves your quality of life significantly. Imagine your battery draining in the middle of the night and switching off the lights. You will have to start using electricity which is very expensive.

To prevent this from happening, ensure you know how to check if the battery is charging. 

Standard 12V battery takes up to 8 hours to charge fully. You cannot assume that your battery is fully charged after eight hours. There are ways you can use to tell if your battery is fully charged.

Use of a solar charge controller

A solar charge controller is an essential component of any solar charging system. It regulates the amount of voltage that reaches the battery. When the battery is drained, the controller allows the 14.4V-14.6V to reach the battery. When the battery is almost full, the controller regulates the voltage to about 13.4V-13.7V

 A controller has a screen that will display the voltage that reaches the battery. 

Use of an inverter

An inverter converts the battery DC power. Most inverters have a screen that displays if the battery is full or almost dead. Other inverters do not have a display screen but make noise or flash different colors to indicate when the battery is almost dead or full.


Several types of meters can be used to measure the charge of a battery. The most common meters used to measure the voltage of a solar battery include a hydrometer, voltmeter, and multimeter.

Tip to make solar batteries last longer

Even though batteries depreciate and eventually die, there are practices you can carry out to increase the longevity of your batteries. Some of the best tips that you can use include;

  • Charge the batteries properly: Allow the battery to charge fully before using it.
  • Clean the solar panel: The solar panel is responsible for harvesting energy from the sun. A dirty solar panel will prevent the battery from charging. 
  • Use large interconnect cables: Large cables reduce the resistance and allow the battery to charge freely.
  • Use distilled water: Additives and electrolytes damage the battery over a long time. It is recommended that you use distilled water as an additive.
  • Equalize the battery: Equalizing a battery involves overcharging the battery once in a while to balance the cells. 

There are other practices that you can do to make your battery last longer.

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