Alkaline AA vs Lithium-Ion Batteries: Which One Lasts Longer Under Different Current Conditions?

Introduction

The lifespan and performance of rechargeable AA batteries compared to lithium-ion batteries vary significantly depending on the amount of current supplied. Let's delve into the details to determine which type of battery performs better under various conditions.

Current Impact on Alkaline AA Batteries

A common misconception is that AA batteries always perform the same regardless of the current drawn from them. However, this is not entirely accurate. When subjected to high current, alkaline AA batteries may provide only about half of their total capacity compared to low current conditions. This discrepancy in performance is crucial to understanding their longevity.

Comparing Lithium-Ion and AA Batteries in Size and Capacity

Let's compare a lithium-ion battery the size of two AA batteries to a pair of AA batteries in terms of voltage and capacity at both low and high current levels.

Lithium-Ion Battery Performance

Voltage (Low Current): 7.2 volts Capacity (Low Current): 2900 mAh

Combining these values, we get:

Total Capacity (Low Current): 20880 mWh (milliwatt-hours)

AA Battery Performance

Voltage (Low Current): 3 volts Capacity (Low Current): 3000 mAh Total Capacity (Low Current): 9000 mWh

When comparing the same size batteries for low current conditions, the lithium-ion battery clearly outperforms the AA battery in terms of capacity, providing about two times the available energy.

Effect at High Current

Now, let's consider the high current scenario where the AA batteries' performance begins to deteriorate much more significantly. At higher current levels, the AA batteries' available capacity drops to about 1500 mAh. This translates to:

Total Capacity (High Current): 4500 mWh

Comparing this with the lithium-ion battery at low current conditions, we find that:

Lithium-Ion Capacity (Low Current): 20880 mWh AA Capacity (High Current): 4500 mWh

Evidently, the difference in performance drops to a significant margin, making the lithium-ion battery nearly four times as effective for high current applications.

Complexity in Comparisons

It is essential to note that the performance comparison does not end here. If we consider the energy requirements of 4 AA cells (6 volts or 5 AA cells (7.5 volts)), we find:

Energy from 4 AA Cells (6 volts): 18000 mWh at low current Energy from 5 AA Cells (7.5 volts): 23000 mWh at low current

However, at high current, the AA batteries' performance drops, and their effective capacity is halved.

For viability under equivalent high load conditions, the AA batteries would likely provide less than half the energy due to their voltage drop and increased internal resistance.

Conclusion

In summary, the choice between alkaline AA batteries and lithium-ion batteries depends on the specific current requirements. For low current applications, lithium-ion batteries outperform AA batteries due to higher energy density. However, for high current or higher load applications, AA batteries may offer more consistent performance at lower current levels, but their capacity drops significantly at higher current demands.