As we have seen in the ever-changing and rather unpredictable environment of electric vehicles, we need to give more attention to the battery health. As the power source for EVs, batteries are exposed to a number of stressors over their lifetime which causes a phenomenon called “battery degradation“. The knowledge of what battery degradation entails, its causes and how they can be prevented is essential to improving the lifespan and efficiency of the vehicles. This post provides and goes a little deeper into the understanding of battery degradation and what you can do to ensure that it does not harm your battery.
I. What is Battery Degradation?
To explicate battery degradation, one has to understand batteries and types of batteries first of all. Among the battery types, lithium-ion batteries are the most commonly used lithium-ion batteries for most portable consumer electronics and electric vehicles. Lithium Iron Phosphate (LFP) batteries are a type of Li-ion batteries that have been gaining more acceptance in electric vehicles and energy storage. Regardless of the type, batteries contain three basic components: an anode, a cathode and an electrolyte. The anode is the covering on which electrons move out in it when it is connecting to a circuit while the cathode is the place of entering of the electrons. These components are usually separated by dividers to prevent direct contact between the anode and cathode. All of these components are stored inside an enclosure, giving the battery cell a recognisable shape.
Battery degradation mainly refers to the phenomenon that the performance of the battery gradually decreases during use. This includes a decrease in battery capacity, an increase in internal resistance, a decrease in charging and discharging efficiency, etc., which ultimately leads to a shortened service life of the battery.
II. What Would Happen If There Is Battery Degradation
It is shown that the degradation of lithium-ion batteries may cause issues such as the decline of charge/discharge rate, diminishing the amount of available capacity and reduced thermal stability. The general capacity of power delivery also significantly decreases in the form of charging time and reduced discharging capacity which in turn lessens the usage time and lifespan of battery. The specific effects are as follows:
- Reduced range: Battery performance degradation is a highly visible problem that manifests in a shortening of the driving range of electric vehicles. As the battery gets old, it becomes less efficient in storing energy, which means the vehicle cannot travel as long on a single charge.
- Longer Charging Times: Old batteries may also somehow take a longer time to charge because they will not be able to recharge at high rates as the new batteries.
- Loss of power: Declining performance batteries may not have the same power storage capacity as before for use in acceleration as will be the case with overall performance.
- Increased Costs: The cost increases because batteries lose their efficiency over time and they may require replacement earlier than planned. In addition, a degraded battery can reduce the resale value of an electric vehicle.
III. Causes of Battery Degradation
Now that we know what battery degradation is and its effects, let’s explore the causes behind this pesky problem.
1. Cycling
Typically any time a battery is used for a charge-discharge cycle it takes some amount of stress. This process is known as cycling and it is considered one of the biggest causes of battery degradation. In the long run, cycling will cause the batteries to employ and wear out several internal components resulting to reduced capacity.
The more often a battery is cycled in an EV, the faster it will degrade overall. Therefore it is essential that batteries are managed properly to extend their usable life. However, letting a battery stay for a long time and not charging or overcharging can also cause the battery to degrade even when not in use.
2. Temperature Exposure
Another factor is temperature control because it directly affects the battery’s capacity. Batteries are also susceptible to permanent damage from extreme temperatures, hot and cold, both of which will cause the battery to degrade. High temperatures also increase the thermal stress which degrades the electrolyte of the battery and reduces its capacity. On the other hand, cold temperature deteriorates the chemical reactions within the battery and thus declines its charging capacity.
Fluctuations in temperature can also be disadvantageous because degradation of different parts of the battery cell is not uniform whereby the efficiency and performance of the battery decreases.
3. Operation Causes
The use of a battery can also influence its capacity as to how long it can last in terms of power output is concerned. Other factors like fast charging more often, deep discharging, and keeping SoC high can lead to increased battery wear and tear.
For instance, present features such as fast charging may be advantageous as they take less time compared to other charging techniques but they produce heat and put pressure on the battery. Further, frequent discharging of the battery up to a very low percentage or constant charging of the battery past a certain capacity also contributes to battery degradation.
4. Calendar Aging
Batteries also age naturally, even when they are not being charged or discharged, a phenomenon termed calendar aging. This type of degradation happens through chemical reactions that also happen in the battery when it is not being cycled. Temperature, storage conditions and state of charge of the calendar are some of the factors that affect the calendar aging.
Calendar aging is more likely to happen in batteries that are exposed to high temperatures or those that stay fully charged for an extended time. Such degradation is unavoidable, however, it can be controlled if the product is properly stored and used.
IV. How to Mitigate Battery Degradation
While battery degradation is unavoidable, there are several strategies that battery users can employ to mitigate its effects and extend the battery’s lifespan.
1. Temperature Control
- Optimal Operating Temperature: To minimize the thermal stress of batteries, they should be stored at ideal temperatures(20℃~30℃). It is well understood that both high and low temperatures reduce the life of a rubber product by accelerating its degradation.
- Active Cooling/Heating Systems: In some cases like in EVs, the active thermal management systems control the battery temperatures to ensure they are not too hot or too cold.
2. State of Charge (SoC) Management
- Avoiding Full Charge/Discharge Cycles: Taking batteries to the full charge or even to empty does more stress on the battery, which leads to degrading faster. It is ideal to keep SoC between 20 and 80%.
- Adaptive Charging: Using smart charging algorithms that set charging currents based on the current health state and environment of the battery puts less strain on it.
3. Proper Charging Practices
- Slow Charging: Charging the battery at a lower current or amperage is much less strenuous on the battery than charging at a higher current/amperage. However, fast charging is sometimes necessary for convenience.
- Avoiding Overcharging: Excessive charge voltage results in chemical reactions that cause degradation of battery components. Modern batteries are equipped with protection circuits to prevent overcharging.
4. Cycle Life Management
- Partial Discharges: Rather than fully discharging a battery before recharging, partial discharge cycles (e.g., using 50% of the battery’s capacity) can extend its life.
- Reducing Depth of Discharge (DoD): Low utilization means that the deep depth of discharge (DoD) should not be used because it stresses the battery in each cycle.
5. Regular Monitoring and Maintenance
- Battery Management Systems (BMS): A good BMS checks the voltage, the current, the temperature, and the state of charge to control the battery and avoid conditions that can bring deterioration.
- Routine Health Checks: In the case of battery health and BMS, it is also beneficial to check the health frequently and reset the BMS to help in observing the signs of decline and establishing preventive measures.
Conclusion
Battery degradation is one of the negative aspects of experiencing the usage of electric vehicles, however, its effect can be minimized if certain measures are put into practice. By understanding the causes of battery degradation and implementing strategies to mitigate it, EV owners can extend the life of their batteries, ensuring better performance and reduced costs over time. Thus, keeping abreast of the state of battery health will become increasingly relevant as the EV market grows and develops further. If you want to learn more about batteries, contact me to have a discuss!
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