XTAR Visible Mixer VX4 Charger

The VX4 charger uses a 300mA discharge current to test battery capacity. Compared with a professional capacity grading machine, its energy and capacity test accuracy is more than 95%. Under the comparison test of the XTAR lab, with the same test condition, a randomly picked XTAR 1.5V AA 1200mWh battery had real capacity 1161mWh by VX4 charger, and 1129mWh by capacity grading machine. The accuracy error between them is less than 3%.

The capacity grading results of 1.5V rechargeable Li-ion batteries are mainly affected by battery capacity fluctuations, battery energy labeling/claiming methods and charger capacity test standards.

Affected by many factors, the capacity of each battery cell is not exactly the same. For example, the cell capacity fluctuation of the XTAR AA 4150mWh Li-ion battery is about ±5%. The built-in step-down circuit and protection board cause some loss in energy output. The energy loss of XTAR 1.5V lithium batteries is about 10%, which means a higher conversion efficiency in the industry.

Since 1.5V rechargeable Li-ion batteries are an emerging type of battery, different brands use various nominal energy labeling methods. There are mainly: 1)Severe overrated: actual energy is lower than 80% of the nominal energy. 2)Taking the cell energy as the battery’s nominal energy, the actual energy is about 85% to 95% of the nominal energy. 3)Genuine rated: actual energy is about 100% of the nominal energy. 4)Over the rated: actual energy is more than 100% of the nominal energy.

Additionally, the chargers from different brands have various capacity grading standards. Generally, the higher the discharge current, the lower the measured capacity and energy. The VX4’s capacity test standard for 1.5V rechargeable Li-ion batteries is 300mA discharge current and 0.5V cut-off voltage.

As a new generation type, 1.5V AA and AAA rechargeable Li-ion batteries are less common in the market than the regular disposable alkaline and 1.2V NiMH batteries. While the manufacturers becomes more and more, resulting in varying quality and chaotic market. As a leader in the cylindrical lithium battery industry, XTAR has always been at the forefront of technological innovation. We aim to help users easily identify overrated battery and lead the industry toward high-quality and standardization.

The capacity test is greatly affected by the discharge current. The higher the discharge current, the lower the measured capacity, and vice versa. The discharge current of VX4 is 0.3A, while the international testing standard IEC 61960-3:2017 specifies a 0.2C discharge rate to test the nominal capacity of 3.6/3.7V Li-ion batteries. For example, the nominal capacity value of 26650 6000mAh battery comes from the test with 1.2A discharge. If you test it with VX4 charger, the much lower discharge current would lead to a higher test value than the nominal capacity.

No, it won’t. According to the international testing standard IEC 61960-3 2017, the discharge cut-off voltage for 3.6/3.7V Li-ion batteries is 2.5V.

There are mainly three factors. The first is the test temperature, the optimal is 20±5℃. Both low and high temperatures will affect the battery discharge performance, and then directly affect the discharge capacity.

The second is the discharge current. The international testing standard IEC 61960-3:2017 specifies a 0.2C discharge rate to test the nominal capacity of 3.6/3.7V Li-ion batteries. There is no unified test standard to test the nominal capacity of 1.5V rechargeable Li-ion batteries. Common test methods use 0.25A discharge for AAA batteries and 0.5A discharge for AA batteries. The higher the discharge current, the lower the discharge capacity. The worse the battery performance (higher internal resistance), the greater the impact of the discharge current.

The third is the cut-off voltage. The IEC testing standard specifies a 2.5V cutoff voltage for 3.6/3.7V lithium-ion batteries. The higher the cut-off voltage, the lower the discharge capacity. To highlight better performance, some 3.6/3.7V Li-ion batteries on the market may use 0.5C discharge or a 2.8V cut-off voltage to measure and claim the nominal capacity.

Higher internal resistance restricts current flow, resulting in poor discharge performance. It also consumes some energy. With high internal resistance, the heat loss increases, thereby reducing the battery’s usable capacity.

According to the test of the XTAR lab on professional capacity grading machine, the actual test result of Tenavolts AA 2775mWh battery is around 3200mWh, while another Tenavolts AA 3300mWh battery also measured around 3200mWh. This suggests that both models may use the same batch of cells. Currently, a pack of four 2775mWh batteries is priced at $30.99 on Amazon. A pack of XTAR four AA 3300mWh batteries is $23.99 on Amazon.

The labeling standard for the nominal energy of XTAR AA 4150mWh and AAA 1620mWh battery is: the energy comes from the cell energy before loss, and the capacity comes from the real measurement at 1.5V output. Due to the cell has 10% output loss, the battery capacity measured by VX4 charger is the output capacity after loss.

The advantage of using the 3.6V cell’s energy as the battery nominal energy is it helps avoid significant fluctuations in energy output due to conversion efficiency. First, the conversion efficiency of constant voltage step-down circuits will improve with industry advancements. Second, there are significant differences in conversion efficiency among different step-down circuits. For example, the conversion efficiencies of the constant voltage step-down circuit is 90%, while that of the linear step-down circuit is only 80%.

Don’t worry too much. After inserting the battery, VX4 will take about 3 minutes to identify the battery type. After that, the correct battery type will be displayed on the screen.