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Is it Bad to Fully Discharge a Lithium-ion Battery

John Marius
John Marius
—
12/06/2024

Lithium-ion batteries, commonly known as Li-ion batteries, are widely employed in solar power kits, serving as excellent power sources for solar panels, rv leisure batteries, and trolling motor batteries. They are also suitable for powering tools during solar power maintenance. These batteries are characterized by their low-maintenance nature, high efficiency, and long lifespan.

One common question that arises is whether it is detrimental to fully discharge a lithium-ion battery. In this article, we will explore this question in depth, providing a clear understanding of the impact of fully discharging lithium-ion batteries and offering best practices for their optimal use and maintenance.

Summary First

While lithium batteries with BMS protection can safely undergo full discharge or charge temporarily, prolonged storage at 0% is dangerous because the BMS continues drawing a small standby current, which may eventually drain cells to 0V and cause permanent damage - occasional full discharges are acceptable but should be recharged within 24 hours. Similarly, storing at 100% charge accelerates degradation due to high electrochemical stress.

For daily use, maintaining 10-90% charge minimizes wear, while long-term storage at 40-60% charge optimizes battery lifespan by balancing voltage-related aging factors.

litime lifepo4 lithium ion batteries

Understanding Charging Cycles

A charging cycle refers to the process of charging a rechargeable battery from its discharged state to its fully charged state and then discharging it again. For example, if you use half of your battery's capacity and then recharge it fully, that would count as half a charging cycle.

For lithium-ion batteries, a charging cycle is typically measured from a 0% to 100% charge. It's important to note that each time a battery undergoes a full charging cycle, it contributes to the overall degradation of the battery's capacity over time. This degradation is often measured in terms of the number of charging cycles a battery can undergo before its capacity diminishes significantly.

Deep Charging VS Shallow Charging

Deep charging and shallow charging refer to the depth of discharge during the use of rechargeable batteries, particularly lithium-ion batteries.

  • Deep Charging: This occurs when a battery is significantly discharged before being recharged. In the context of lithium-ion batteries, deep charging involves discharging the battery to a relatively low capacity level, such as 20% or lower, before recharging it. Deep charging can put more stress on the battery, potentially leading to faster degradation over time.
  • Shallow Charging: Shallow charging, on the other hand, involves recharging the battery when it has only been partially discharged. In the case of lithium-ion batteries, this might involve recharging the battery when it's at 50% capacity or higher. Shallow charging generally puts less stress on the battery and can contribute to a longer overall battery lifespan.

A lithium battery typically lasts for 300 to 500 charging cycles. Assuming a full discharge provides a capacity of X, lithium batteries can deliver or supplement a total power of 300X to 500X over their lifetime if the capacity decline after each charging cycle is not considered. If half of the capacity is used each time, these batteries can be charged 600 to 1000 times, and if 1/8 of the capacity is used each time, they can be charged 2400 to 4000 times.

A LiTime LiFePO4 lithium deep cycle battery last 4000 cycles when discharged to 100% of its capacity. If half of the capacity is used each time, LiTime battery can be charged 8000 times, and if 1/8 of the capacity is used each time, it can be charged 32000 times.

Consequently, the number of times a lithium battery is charged is unpredictable when done at random. In essence, regardless of how a lithium battery is charged, a total of 300X to 500X of power is always added. Therefore, it may be concluded that the life of a lithium battery is proportional to the battery's overall charge, not to the number of charges. Both deep charging and shallow charging have similar impacts on lithium battery life.

Lithium batteries benefit more from shallow discharge and shallow charging. Deep lithium battery charging is only necessary when the device's power module is calibrated for lithium-ion batteries. As a result, lithium-ion-powered devices are not restricted by the process and may be charged at any time without compromising battery life.

Shallow cycle charging is designed to enable batteries to provide short bursts of energy and not be used for an extended period before being fully charged. Deep cycle ensures your battery can manage long-term use by reaching much below 50% discharge before needing to be recharged.

It's important to note that shallow cycle batteries dislike being depleted over extended periods. To care for your shallow cycle battery and extend its life, consider installing a discharge control circuit that turns off the battery when it's drained to around 50% and replenishes it as soon as possible. Additionally, having a smart charge/discharge monitor is crucial for maintaining the health of your deep cycle or shallow cycle battery.

How Does Storage Affect Battery's Lifespan

Due to their minimal capacity loss during dormancy compared to other battery types, lithium-ion batteries are among the most convenient options for storing solar energy. This is particularly advantageous in scenarios where solar power is infrequently utilized, such as in a summer cottage, thanks to their low self-discharge rates.

The way you store a battery can significantly impact its lifespan. Here are some key factors to consider:

1. Temperature: High temperatures can accelerate the degradation of battery materials and lead to a shorter lifespan. Similarly, storing batteries in extremely cold temperatures can affect their performance. It's best to store batteries at moderate temperatures to maintain their health.

2. State of Charge: Storing batteries at full charge or complete discharge for extended periods can be detrimental to their lifespan. Ideally, lithium-ion batteries, for example, should be stored at around 50% charge to minimize degradation.

3. Humidity: Excessive moisture can lead to corrosion and damage the internal components of the battery. Storing batteries in a dry environment is important for their longevity.

4. Protection from Physical Damage: Protecting batteries from physical damage, such as impacts or crushing, is crucial. Any physical damage can compromise the integrity of the battery and reduce its lifespan.

5. Protection from Short Circuits: Storing batteries in a way that prevents accidental short circuits is important for safety and to maintain the health of the battery.

6. Avoiding Prolonged Inactivity: If a battery is left unused for long periods, it can suffer from self-discharge and chemical changes that may impact its ability to hold a charge.

In summary, the storage conditions play a critical role in preserving a battery's lifespan. Proper storage involves maintaining moderate temperatures, storing at the appropriate state of charge, protecting from physical damage and short circuits, and avoiding prolonged inactivity. Following these guidelines can help maximize the lifespan and performance of batteries.

How to Maintain the Health of Your Lithium-Ion Battery

Understanding how to maintain the health of lithium batteries during charging is crucial. "Battery life" refers to the amount of time a device can operate before needing a recharge, while "battery lifespan" refers to the duration before a battery needs replacement. The combined actions taken with your device significantly impact both battery life and lifespan. Regardless of usage, there are ways to help preserve the battery.

Extending battery life reduces the economic and environmental impact of manufacturing new batteries, including raw material consumption, extraction impacts, greenhouse gas emissions, and the disposal of spent batteries.

It's important to understand not only what sustains the battery's current charge but also how to properly care for the battery, which is equally crucial. This ensures the battery operates more effectively. Here are some tips for maintaining the health of your lithium-ion batteries:

1. Use Partial Discharge Cycles

Lithium-ion battery packs should not be fully depleted and recharged frequently (deep-cycling). Utilizing only 20 or 30 percent of the battery's capacity before recharging significantly improves battery life. Five to ten shallow discharge cycles are roughly equivalent to one full discharge cycle.

2. Avoid High Charge and Discharge Currents

High charging and discharging currents will reduce the battery's cycle life, as they put significant strain on the battery.

3. Limit the Battery Temperature

Minimizing battery temperature extremes, especially avoiding charging below 0°C, enhances battery health. Charging at below-zero temperatures can stimulate metal plating, potentially leading to an internal short circuit, making the battery volatile and hazardous. Utilizing the batteries built with low-temperature charging protection or self-heating function are recommended for the area with long winter time.

lithium battery with battery management system

4. Avoid Charging Lithium Batteries to 100% Capacity

Lowering the float voltage can improve the cycle and lifespan of the battery at the cost of capacity. A float voltage dip of 100 to 300 mV can improve cycle life by 2 to 5 times or more.

5. Avoid Overcharging

Overcharging can accelerate irreversible capacity loss and induce interior metal plating, leading to an internal short circuit, overheating, and instability.

6. Avoid High Moisture

Storing or using lithium-ion batteries in high-moisture environments can harm battery life and performance.

7. Use an Appropriate Battery Charger

The float voltage and charge termination mechanism of a battery charger play a major role in increasing battery lifespan. Chargers with lower float voltage can help extend battery life. Chargers using minimum charge-current termination techniques can also extend battery life.

Using a charger designed for lithium-ion batteries can help customize the charge and limit harm to your battery. The charger that shipped with your battery is the best option. Here's the charging voltage for recommended.

lifepo4 battery charging voltage 

LiTime LiFePO4 Lithium battery chargers are built for charging lithium batteries properly, and provide multilevel protections of over-temperature, reverse polarity connection, output short circuit, over-current and output over-voltage. 

Related reading: Can I Charge Lithium Battery with A Normal Charger?

Conclusion

In conclusion, fully discharging a lithium-ion battery can have detrimental effects on its overall health and performance. By understanding the impact of deep discharges and following best practices for battery use and maintenance, users can prolong the lifespan and optimize the performance of their lithium-ion batteries. Ultimately, by adopting these practices, individuals can ensure that their devices and systems powered by lithium-ion batteries continue to operate reliably and efficiently for years to come.

By adhering to these guidelines, individuals can make informed decisions about the use and care of their lithium-ion batteries, ultimately maximizing their longevity and performance.

This article serves as a comprehensive guide to understanding the impact of fully discharging lithium-ion batteries and provides actionable recommendations for users to maintain the health of their devices' power source.

John Marius
John Marius
John Thompson, an automotive engineer with 15+ years of EV and lithium battery experience, holds a Master’s in Electrical Engineering from Stanford. He’s passionate about advancing battery tech and promoting green energy.

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