What Affects the Lithium Battery Life and How to Calculate It

With the advent of 1.5V rechargeable lithium-ion batteries, an increasing number of users are turning their attention to related discussions, and battery life is one such topic of interest. We’ve observed comments on Amazon about the battery life of these cells compared to AA NiMH batteries. In this article, we will delve into the factors influencing battery life, how to calculate it, and some common FAQs.

What Are the Key Factors Affecting the Battery Life?

Battery life is influenced by several key factors, as below:

Battery Capacity: Battery capacity is typically measured in milliampere-hours (mAh) and represents the product of a battery’s current and time. Higher capacity batteries generally provide longer battery life.

Device Power Consumption: Device power consumption refers to the rate at which a device consumes electrical energy during operation. Devices with lower power consumption tend to offer longer battery life under the same capacity since the battery depletes more slowly.

Usage Patterns: The way and frequency with which a device is used can significantly impact battery life. Continuous high-load usage will deplete the battery faster, whereas intermittent use or standby mode can extend battery life.

Temperature: Battery performance may weaken in extremely cold or hot environments.

Battery Type: Different battery types, such as alkaline, lithium-ion, NiMH, etc., possess distinct electrochemical characteristics that influence their performance in various applications. For instance, lithium-ion batteries typically offer longer battery life under the same capacity.

Current Demands: Some devices may require higher electrical currents to meet their operational needs, which can result in faster battery depletion. If the battery cannot supply the required current, battery life may be shortened.

Charge and Discharge Efficiency: Different types of batteries exhibit varying efficiencies during charging and discharging. Some batteries may lose less energy during these processes, thereby providing longer battery life.

Self-Discharge Rate: Various battery types have differing self-discharge rates. Batteries with higher self-discharge rates lose charge more rapidly when not in use, thereby reducing battery life.

Voltage Stability: Battery voltage stability also plays a role in battery life since certain devices require stable voltage levels, like those VR games, RC toys.

Charge Cycle Lifespan: Battery life is typically limited by the number of charge cycles it can undergo. As the number of charge and discharge cycles increases, battery performance may degrade, impacting battery life.

In real-world usage, these factors interplay and collectively influence battery performance and longevity.

Are Device Power Consumption and Current Demand the Same Thing?

Device power consumption and current demand are not identical concepts. They are related to some extent but still have distinct differences:

Device Power Consumption: it refers to the overall rate at which a device consumes electrical energy when in operation, typically measured in watts (W). This concept takes into account various factors, including current demand, voltage, time, and the device’s overall energy usage. It provides information about the overall energy efficiency of the device, considering how various factors affect energy consumption.

Current Demand: it is the specific amount of current a device requires during operation, typically measured in amperes (A). It represents the rate at which a device draws current from a battery or power source. Current demand is often a component of device power consumption, but it doesn’t provide the full picture. Different devices may have different current demands for the same power consumption, depending on factors like voltage and resistance.

How to Calculate Battery Life?

There are two crucial indicators for calculating battery life: battery energy (typically measured in mWh) and device power consumption (also measured in mWh). While batteries are often rated with their capacity (usually measured in mAh). The relationship between battery capacity and battery energy (mWh) depends on the battery’s voltage. Here is the formula:

Battery Energy (mWh) = Battery Capacity (mAh) × Voltage (V)

Battery Life (hours) = Battery Energy (mWh) / Device Power Consumption (mWh)

The ratio of battery energy to device power consumption can help you understand how the battery performs under different conditions and how long it can sustain at a specific power demand.

However, it’s important to note that this calculation formula does not take the following variables into account:

Battery Lifespan: Reduced battery lifespan can result in decreased energy output over time, thus shortening battery life. High-frequency full charge and discharge cycles, along with prolonged improper use, can accelerate battery aging, leading to a rapid decline in cycle life.

Battery Charge and Discharge Efficiency: Different types of batteries have varying charge and discharge efficiencies.

Usage Patterns: The above calculation formulas do not consider device usage patterns, such as on-time, standby time, and high-load periods.

Self-Discharge Rate: Batteries with higher self-discharge rates can lose charge more quickly during prolonged periods of non-use, thus shortening battery life.

While the simple formula provides an estimate, in practical applications, more detailed information and models are needed to predict battery life more accurately.

Why do rechargeable AA lithium-ion batteries have different battery life than AA NiMH batteries of the same capacity?

Some users who have purchased AA lithium-ion rechargeable batteries have feedback shorter battery life compared to AA NiMH batteries of the same capacity. Why is this the case?

As mentioned earlier, battery life is influenced by a multitude of factors, such as battery type, device power consumption, battery voltage and current requirements, self-discharge rate, battery lifespan, environmental conditions, and usage patterns. Without considering other factors, the calculation of battery life is also influenced by battery voltage. Even with the same capacity, 1.5V lithium-ion batteries and 1.2V NiMH batteries have different discharge voltage curves. 1.5V lithium-ion batteries maintain a constant high voltage output of 1.5V, while the voltage of 1.2V NiMH batteries gradually decreases during discharge.

If these two types of batteries are used in low-power devices, such as alarm clocks and TV remote controls, the device requires a relatively broad voltage range, and it can function normally even at lower voltages. However, if a constant 1.5V high voltage is continuously applied, the battery will be quickly depleted. On the other hand, NiMH batteries will deplete their energy at a slower rate.

If they are used in medium to high-power devices, such as VR game controllers, the devices are sensitive to voltage levels. When the battery voltage drops below 1.1V, the device may determine that the battery is low, resulting in controller disconnection or unstable signal transmission. When using rechargeable 1.5V lithium-ion batteries with a constant voltage output, both overall performance and battery life are improved. However, with 1.2V AA NiMH batteries or alkaline batteries, the voltage drops rapidly and the device quickly misinterprets it as low battery, leading to shorter battery life compared to 1.5V lithium-ion batteries.

Conclusion

As discussed above, battery life is influenced by a multitude of factors. Therefore, we should not hastily judge the quality of a battery solely based on its shorter usage time in certain devices. It is essential to conduct a comprehensive evaluation, taking into account the battery’s specifications, device power consumption, and actual usage patterns.