I don’t know about you, but I’ve almost completely switched from regular AA batteries to rechargeable lithium batteries. I’m currently trying out XTAR’s latest 1.5V AA lithium-ion battery, which claims to have an impressive capacity of 4150mWh(2500mAh). Is this true? Let’s take a closer look.

Overall Overview

Its appearance looks just like a regular AA battery, But inside, it has a intelligent control circuit that manages charging and discharging, and step-downs the voltage from 3.6V to the needed 1.5V. The battery is marked with the brand name, positive and negative poles, some certification and recycling info. The voltage of 1.5V, and the capacity is 2500mAh and 4150mWh. Generally, the capacity of high-quality AA batteries does not exceed 2000mAh, so 2500mAh is quite high, about 25% more. This nominal capacity seems unusual, and I will verify it later.

Capacity Testing of Energizer, Duracell & GP SUPER

I used the Imax B6 Mini battery tester to measure the capacity and voltage curve of the batteries. In order to evaluate the performance of XTAR 4150mWh AA Lithium batteries, I decide to make a comparison with other reputable brands such as Energizer and Duracell. So, I purchased some of their alkaline batteries. However, the capacity test results of these two brands were disappointing.

The capacity of the Energizer battery did not meet the expected standards, and the voltage performance of the Duracell battery was also abnormal. I checked all the batteries were within their validity period. I felt I had wasted a lot of money and even suspected they are fakes.

The test results are as follows:

• Continuous Discharge Current: 100mA

• Duracell

• Nominal Capacity:2850mAh

• Test Capacity: 966mAh

• Energizer

• Nominal Capacity: ＞2000mAh

• Test Capacity: 1146mAh

I decided to try GP SUPER AA alkaline batteries, which are easily available in supermarkets and have proven to be reliable over the years. And indeed, under the same battery tester, the GP SUPER battery had a capacity of 2306mAh, as expected. In addition, with a continuous discharge at 300mA, the result was still around 2000mAh.

• Continuous Discharge Current: 200mA

• GP SUPER: 2306mAh

Capacity Testing of XTAR & GP SUPER

Then I tested eight XTAR 4150mWh AA Li-ion batteries using the same battery tester, at continuous discharge currents of 200mA, 500mA, and 1A. The results showed that the capacity and performance of XTAR batteries were better than GP SUPER batteries. In the diagram below, I’ve listed the highest and lowest test results at each current, with the other six batteries’ results between these two values.

One thing worth noting is the voltage curve. For example, in the 200mA test, the XTAR #7 battery showed reliable performance, maintaining a stable 1.5V for about 11 hours and lasting around 14 hours in total. I’ve reviewed similar 1.5V AA lithium batteries before, and while their stable voltage is a strong point, users might suddenly face a dead battery. Regular batteries gradually reduce voltage as they work, prompting devices to alert users to replace them. XTAR battery also can do this. You can see from voltage curve that when the battery is exhausted, the voltage will drop to 1.1V, thus reminding you to replace the battery in time.

• Continuous Discharge Current: 200mA

• XTAR #7: 2648mAh

• XTAR #4: 2628mAh

• Continuous Discharge Current: 500mA

• XTAR #3: 2454mAh

• XTAR #6: 2363mAh

• Continuous Discharge Current: 1A

• XTAR #3: 2310mAh

• XTAR #5: 2285mAh

The Energy Comparison of XTAR & GP SUPER

Also, it’s often mentioned that comparing capacity(mAh) without including voltage is inaccurate. I took this into account, so let’s do some calculations to illustrate this. I selected the two batteries with the best test results at 200mA continuous discharge:

• XTAR Energy：2.648mAh x 1.44V=3.81Wh

• GP SUPER Energy：2.306Ah x 1.2V=2.77Wh

It can be found that the capacity of GP SUPER AA alkaline batteries is no bad, but XTAR AA Li-ion battery is still in the lead, exceeding GP by more than 1Wh.

Conclusion

XTAR 4150mWh AA Lithium-ion batteries have a charging cycle of at least 1200 times, while the GP SUPER battery is about 500 times. XTAR Li-ion batteries not only surpass AA alkaline batteries from reputable manufacturers in capacity but also have a significant advantage in cycle life. Although XTAR batteries may seem expensive at about $7.50 each, even if the battery only reaches half of its nominal life, this battery is still very cost-effective in the long run.

FAQ

Why choose 1.44V when calculating the energy(mWh) of XTAR 4150mWh AA Lithium battery?

The test capacity of XTAR battery samples is 2648 mAh.

Since when discharged 78-85% of the time the battery produced 1.5V and 15-22% of the time 1.1V, the average voltage during discharge turned out to be 1.44V.

Therefore, the actual energy shown by the batteries is 2648mAh x 1.44V =3181mWh.

4150mWh is the total power of the internal cell (3.6V x 1150mAh). After voltage step down to 1.5V, there are losses. And the discharge efficiency of the battery cell is around 90% to 92%. The final output capacity is around 2500mAh, and energy is around 3750mWh. (2500 x 1.5/4150≈90%). Since testing conditions couldn’t be exactly the same, the above testing results is reasonable.