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How Long Does A Solar Battery Last At Night?

Factors like battery size, energy use, weather, and efficiency affect how well a solar battery works. Solar batteries store energy from the sun for use when it’s night, cloudy or power outage. But how long does a solar battery last at night? We’ll look into this, and what happens when a solar battery runs out of power.

How Long Does a Solar Battery Last at Night?

Solar Battery Last At Night

Solar batteries are essential for providing power to homes during the night when solar panels are not generating electricity. The majority of solar batteries on the market today typically last between 5 and 15 yearsThe length of time a solar battery can last at night depends on factors like battery capacity, energy consumption, and the efficiency of your solar system. 

To estimate how long your solar battery will last, consider your energy needs, the capacity of your solar system, and the type of solar battery system setup you have. Households with high energy usage may need to install multiple batteries. Additionally, taking into account peak sunlight hours and preparing for cloudy days can help ensure a continuous power supply and optimal system performance.

Without using high-energy appliances like electric heaters or air conditioners, a 10 kWh battery can support essential household functions for at least 24 hours, and possibly longer with careful energy management. This provides a general idea of how long does a solar battery last at night.

What Happens When a Solar Battery is Empty?

When a solar battery is empty, it has either used all its energy or is partially charged. You will need to use the National Grid for electricity. The impact of a low solar battery depends on the system design and how it is used. Some common results include:

Power Loss

When the solar battery is empty, any electrical systems or devices powered by the battery will stop working, leading to a power outage that affects connected equipment.

Disconnected Solar Energy System

In a larger solar system for a house or business, the system may shut down if a safety feature is activated when the battery’s charge falls below a certain level.

Limited Energy Availability

In systems with energy management features, the availability of stored energy may be limited until the battery is recharged. Some systems may operate in a reduced power mode or shut down entirely, while others may prioritize supplying energy to essential loads.

Reduced Self-Consumption

Solar batteries store excess energy generated during the day for later use. When the battery is empty, the system can only use the energy produced by the solar panels in real-time, as no stored energy is available for self-consumption.

Net Metering

Net metering allows homeowners to feed excess solar energy back into the grid and receive credit for it. When your solar battery is empty, you can draw electricity from the grid using these credits. This ensures a continuous power supply and helps offset electricity costs.

Grid-Tied Systems

Grid-tied solar systems are connected to the National Grid. When your solar battery is empty, these systems automatically switch to drawing power from the grid, ensuring an uninterrupted electricity supply. Grid-tied systems often use net metering to manage excess energy production and consumption efficiently.

Off-Grid Systems

Off-grid solar systems operate independently of the National Grid, relying solely on solar panels and battery storage. When the battery is empty, off-grid systems face a power outage unless there is an alternative power source, such as a backup generator. These systems require careful management of energy use and storage to avoid running out of power.

Understanding these aspects can help you manage your solar energy system more effectively and ensure a reliable power supply, even when your solar battery is empty.

How Do I Know When My Battery Is Fully Charged?

The simplest way to check if your solar battery is fully charged is by measuring its voltage. A fully charged 12-volt battery should read about 12.7 volts, while a 24-volt battery should read around 25.4 volts. You can use a multimeter, which measures voltage, to check this.

However, voltage alone isn’t always a reliable indicator. If the battery has been idle for a while, the voltage might be higher than the actual charge, giving a false reading.

Another method is to check the LED lights on the charge controller. A charge controller regulates the charging process to prevent overcharging and prolong battery life. Most have LED indicators that show the battery’s status. A fully charged battery typically lights up green or blue.

Some charge controllers come with a display screen showing the battery’s voltage, current, and state of charge. These displays are generally more accurate than just checking the voltage.

In summary, you can determine if your solar battery is fully charged by:

  1. Checking the voltage with a multimeter.
  2. Observing the LED lights on the charge controller.
  3. Reading the display screen on the charge controller.

While measuring voltage is straightforward, it’s not always precise. The charge controller’s LED lights or display screen provide a more reliable assessment. Regular monitoring of your battery’s charging status is crucial for ensuring its longevity and getting the most out of your solar power system.

What Can Damage a Solar Battery?

Solar batteries can be damaged by various environmental factors, such as temperature, weather conditions, humidity, and physical damage. Ignoring these factors can lead to battery damage and poor performance.

To avoid these issues, ensure you choose a professional solar system installer.

Here are four factors that can also damage a solar battery:

Electrolyte Loss

High temperatures, fast charging, and overcharging can make sulfuric acid leak out of flooded or unsealed batteries. This can expose parts of the battery plates, reducing performance. In sealed batteries, high charging currents and overcharging can increase temperature and pressure, potentially causing valves to leak gas or electrolyte, leading to irreversible damage. Sealed (or maintenance-free) batteries are especially vulnerable to temperature and overcharging.


During discharge, lead sulfate crystals form on the plates of lead-acid batteries. These crystals are normally converted back to lead and lead oxide during charging. However, if the battery remains partially charged for long periods, the lead sulfate crystals can harden and stop converting back, reducing the battery’s capacity.

This issue is exacerbated at higher temperatures. To avoid sulphation, design your PV system to minimize the duration the battery remains partially charged and ensure a quick return to a full state of charge.

Electrolyte Stratification

Lead-acid battery performance depends on a consistent electrolyte (a solution of sulfuric acid in water) distribution. Stratification, where the denser sulfuric acid settles at the bottom, can occur, leading to uneven acid concentration. This negatively affects battery performance.

Very Deep Discharge

Although deep cycle batteries can tolerate discharges up to 80%, it is best to limit discharge to 50% and reserve 30% for emergencies. Shallow cycling, where the battery is not deeply discharged, extends its lifespan. For instance, EXIDE’s TORR range of solar tubular batteries offers:

1500 cycles at 80% depth of discharge (DoD)

3000 cycles at 50% DoD

5000 cycles at 20% DoD

Allowing a battery to stay partially or insufficiently charged can lead to sulphation. Discharging beyond 80% can cause irreversible chemical changes, leading to significant permanent damage.

While estimating the exact duration a solar battery will last at night is difficult, it generally ranges from a few hours to several days. The battery’s capacity, weather conditions, and geographical location influence nighttime performance.