Solar battery is draining fast

Why Solar Battery Drains Fast and How to Avoid It?

The solar battery is an important part of the solar photovoltaic system. It is responsible for storing the electrical energy converted by the solar panels.

There are different types of solar batteries. The most common are lead acid, lithium, AGM, and gel.

As with all systems, solar batteries can experience problems over time.

One of these problems is that the solar battery will drain quickly and not hold a charge.

which can easily affect the operation of the solar system and the customer’s use.

Today we will talk about the cause of solar battery draining fast and how to avoid it.

How to Check if Solar Battery is Draining?

After a period of use, you may have an idea of how long a fully charged battery can last, and if the current battery does not last as long as expected, then there is likely to be a problem of excessive battery draining.

To check whether your solar battery is draining, you can use a multimeter to monitor the power output of your battery.

Another way to check is to use solar controllers and inverters. They are connected to the battery in real time and can check the status of the battery.

and if it is draining, it will show up in what they’re reading.

Types of Solar Batteries and Their Charging Times

Solar battery is a rechargeable battery. It supports deep discharge and high cycle times.

Gel battery, lead-acid battery, lithium-ion battery are the most common energy storage batteries. They have different charging and discharging duration.

Let’s compare with similarly sized photovoltaic batteries

Lead-acid batteries charge slowly. It usually takes 8-10 hours for a full charge.

Lithium ion batteries charge a little faster during the day. It can take 7-8 hours to fully charge.

AGM batteries charge and discharge slowly, similar to lead-acid batteries.

What Causes Solar Battery Draining?

There are many reasons why a solar battery may discharge too quickly.

Excessive discharging can be caused by the battery itself, problems with other components in the system, or external factors.

We summarize the following.

Charge Controller Issues

A charge controller is used to limit the speed of power being added to or removed from the batteries.

It automatically switches from charging the batteries to maintaining their charge. If it malfunctions, it can affect the battery bank’s capacity to hold a charge. and no warns when the battery drains.

Your Battery is damaged

While solar battery failure can be caused by a number of factors, overcharging, under charging, and sulfations.

Battery damage can also cause the battery to fail to charge and discharge too quickly.

Extreme Weather Condition

Extreme weather conditions such as rain, snow, or cloud cover can reduce solar power generation and drain batteries faster than usual.

Parasitic Draw

Solar batteries can be drained quickly because of a phenomenon called “parasitic draw”. This occurs when an appliance is in standby mode and continues to draw power, even when it is shut off.

For example, solar batteries can be drained quickly by a television or other type of electronic device that is in standby mode and continuously consuming power.

Parasitic draw is particularly problematic for people who rely on solar power for their appliances.

Internal Problems

Over-discharging is a common issue that can occur in solar batteries. Over-discharging can lead to battery overheating and failure. Low output voltage, low current, and sulfation are common internal problems that can lead to battery depletion.


Overheating can lead to battery failure. If the battery gets too hot, it may cause cells to rupture, leading to a loss of electrolyte and eventually, cell ignition.

Too Long between Battery Recharges

Charging and discharging batteries can cause battery drain if solar panels are not compatible with the battery type or if not enough power is generated from the solar PV.

Not Enough Charge

A battery can be partially drained if the solar panel capacity is not sufficient to charge it fully during the day.

You should recharge batteries at 50% for lead acid batteries and 35%-40% for lithium batteries, and 85%-95% to use the battery for longer periods.

Not Using a Charge Controller

A charge controller is a vital component of solar battery system, regulating voltage and current to ensure that batteries get charge and not overcharge.

It is critical to use a charge generator to protect them from overcharging and ensure they operate at their best capacity.

without a charge controller, solar batteries may discharge faster than they are able to recharge, causing the internal charging system to wear out quickly.

Putting a Fully Discharged Battery in Storage

A battery should never be fully discharged or charged when stored for long time.

It is recommended to keep the battery at 85% full when stored. Discharging a battery too much can damage the battery cells and reduce its life span.

Poor Battery Maintenance

Overcharging and undercharging of a battery can lead to battery failure and eventual draining.

Poor battery maintenance can lead to battery drain.

Increased Load

Over-discharge is an important issue with solar batteries, especially when they are used to store power from solar panels.

The high load of solar batteries can lead to faster discharge, resulting in a drop in voltage levels below a preset threshold.

This over-dis discharge can dramatically reduce battery life and ultimately cost savings.

Defective Charge Controller or Inverter

A defective charge controller or inverter can lead to voltage spikes and dips, which can disrupt the battery charge or drain the battery without cutoff. This in turn may lead to damage or loss of battery capacity.


Solar batteries, like other types of batteries, are affected by aging degradation.

The performance of a solar battery can degrade with time due to factors such as discharge and charge cycles, over-discharging, and short-circuiting.


Heat can lead to faster battery wear and discharge. Extreme cold temperatures can also have an effect on the life of solar batteries.

The high temperature of solar batteries can lead to faster chemical reactions, causing them to drain more quickly.

Battery quality

When solar batteries drain faster than normal, it’s usually due to one of two reasons: either the battery’s battery quality is low or over-discharging protection in the battery fails to function properly.

Another reason solar batteries drain faster than normal is that solar panel voltage drops to 0 at night. Without diodes or charge controllers, charge current reverses and drains the battery instead of charging it.

Best Practices for Maintaining a Solar Battery

When maintaining a solar battery, it is recommended to keep the battery at 85% full

To ensure optimal battery performance, it is essential to follow best practices for charging and discharging the solar battery.

The charging process should be complete within 14-20 hours of solar exposure, while the discharge cycle should be shorter than 3-5 days.

It is essential to monitor the SoC level of solar batteries and adjust the charging and discharging cycles as needed to ensure the battery ends each day at or close to 100%.

Quality MPPT Charge Controller and inverter with Over discharge Protection.

Low Voltage Disconnect Switch to help auto cut off when battery voltage is low.

Tips to Make a Solar Battery Last Longer

When using solar power, charge the batteries fully before using them. This will provide the batteries with more power than they would normally have and ensure that they last longer.

Regularly clean the solar panel to ensure optimal performance and longevity.

Use interconnect cables of proper size to maximize power transfer between the solar panel and battery. This will allow for increased efficiency and power output, which could prolong battery life.

Use distilled water as an additive to improve the electrolyte in your battery cells, which could also help increase its lifespan.

Lastly, equalize your battery by a ZHCSolar battery balancer.

How to Replace Solar Battery Diodes and Fix Draining

If you notice that your solar battery isn’t holding a charge as long as it should, you may have just one issue – solar battery diodes.

These are the essential components of solar batteries that convert the solar power into DC power for charging batteries.

To fix solar battery draining issues, you need to replace solar battery diodes with high-quality ones. Higher-quality solar battery diodes can withstand greater voltage and current than the cheaper variants.

What Are the Latest Technologies for Avoiding Fast Draining in 2023?

There are a number of advancements being made in solar battery technology to help avoid fast drainage.

For example, MPPT charge controllers and inverters have features that protect batteries from over discharge, which can prolong their life. In addition, low voltage disconnect switches help stop the battery from draining when the voltage is low.

How to Prevent Solar Battery Drain?

To prevent energy from being wasted, you can also utilize a high quality solar charge controller. This will help you control the amount of solar power flowing into the battery, preventing it from overcharging or undercharging.

Low Voltage Disconnect Unit also helps protect battery from drain fast.

The Impact of Sulfation on Solar Batteries

Sulfation is a natural process that happens to batteries over time. It causes the battery to lose power and discharge more quickly.

Frequently Asked Questions

What are some common causes of solar battery drains?

Some common causes of solar battery drains are due to solar panel capacity not being sufficient to charge the battery fully.

Another cause is over-discharge of a battery. Over-discharging occurs when the load draws more current than the battery can provide.

incorrect wiring,improper charging controller installation are also some causes.

Are solar battery drains always bad?

Solar battery drains can be normal, even when solar energy usage is low. This is because solar batteries naturally discharge over time as a result of charging and discharging.

What can I do to avoid solar battery drains in the future?

One thing you can do to avoid solar battery drains in the future is to calculate the correct number of solar batteries needed for your system and utilize over discharge protection by charge controller and inverter.

How can I diagnose and fix solar battery drains?

To diagnose and fix solar battery drains, start by checking the controller for damage or programming reset. Next, use a multimeter to check if the battery is dead or broken.


Although solar batteries are an efficient and cost-saving solution for off-grid energy storage, they do have their drawbacks. If you want to avoid solar battery draining, it is essential to follow a few basic tips.

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