Review of the XTAR 18650 4000mAh Protected Battery

Today, I want to talk about a new 18650 battery from XTAR. Previously, I reviewed an 18650 battery from another lithium battery brand. This XTAR battery also claims a 4000mAh capacity and comes with a protection circuit. To get a full understanding of its performance, I conduct in-depth testing.

Here are the Battery Nominal Specifications:

· Nominal capacity: 4000mAh

· Nominal energy: 14.4Wh

· Nominal voltage: 3.6V

· Max continuous discharge current: 10A

· Cycle life: 600＋

· Storage temperature: -20℃ – 40℃

· Operating temperature: -20℃ – 60℃

· Weight: ≤50g

· Dimensions: φ18.40mm x H69.20mm

The battery comes in blue and white heat-shrink wrapping. The positive terminal is slightly raised, about 1mm, while the negative terminal is flat. It also includes multiple safety features, such as over-discharge protection, over-charge protection and short-circuit protection.

Physical Performance Test

I measured the two batteries using a calibrated electronic scale and caliper:

· Sample 1: 49.4g, φ18.40mm x H69.27mm

· Sample 2: 49.49g, φ18.29mm x H69.20mm

I also measured the XTAR unprotected 18650 battery, which is about 65mm in length. In other words, the protected version adds about 4.2mm to the length.

Electrical Performance Test

I conduct testing using the ACK 75.10.20.2 chemical power analyzer. The steps are as follows:

· Discharge at a constant current of 800mA to 2.5V.

· Pause for 1 hour.

· Charge at a constant current of 2A to 4.2V, until the current drops to 100mA.

· Pause for 1 hour again.

· Discharge at a constant current of 800mA to 2.5V.

I also followed the same steps for testing discharge currents at other levels.

1. Discharge Performance

Here are the discharge curves for the battery at different discharge currents. The vertical axis shows the voltage (V), and the horizontal axis shows the discharged capacity (Ah). The brown line represents the variation in internal resistance (IR).

The test results show that:

At a discharge current of 0.8A, the capacity is close to 4000mAh, which matches the manufacturer’s claimed value. Even at a high discharge current of 9A, the capacity is still greater than 3600mAh.

When the battery is fully charged, the IR is 28mΩ and when fully discharged, it is 31mΩ, with only a 3mΩ change, showing excellent stability. This is very close to the values measured with the YR1035 Plus battery IR meter (26.9mΩ/27.8mΩ). If I am testing a lead-acid battery, the change in internal resistance would be much larger.

2. Protection Circuit Test

I also test at what voltage the battery’s protection circuit would be activated. The test is very simple. First, I charge the battery to 3V, then discharge it at 800mA after a short pause.

The results show that both batteries triggered protection at 2.49V, with a voltage difference accurate to three decimal places. This level of precision is impressive for high-quality protected lithium batteries. In contrast, an unprotected Panasonic battery I bought on AliExpress had a much lower protection threshold, ranging from 2.3V to 2.35V. Such deep discharge could negatively impact battery life.

Back to the XTAR battery, its protection circuit triggers at 2.49V, which is an excellent indicator. This prevents deep discharge, helping to extend the battery life.

3. Temperature Test

Under different discharge currents, the battery performance is as follows:

0.8A: Battery temperature is 28.7°C.

4A: Battery temperature is 42.5°C.

8A: Battery temperature is 59.9°C, which is within the acceptable range.

9A: Battery temperature is 64.6°C, slightly exceeding the 60°C limit.

4. Capacity Test

Let’s talk about the battery capacity. Compared to the earlier Panasonic NCR 18650B, this XTAR 18650 battery has nearly 20% more capacity. I guess this improvement is due to advancements in the electrode formula, such as adding nickel oxide, and increasing the number of electrode layers by reducing the thickness of the aluminum and copper foils inside the battery.

However, this could also make heat dissipation more challenging and limit the maximum discharge current. The XTAR battery exceeded 60°C during a 9A discharge, which is likely caused by this.

The table shows the final results of the battery test, listing key performance indicators such as capacity, energy and temperature:

》Line 6 shows that at a 0.8A discharge current, the first sample has a discharge capacity of 3982mAh, and the second sample has 4006mAh. As we can see, the real performance matches the manufacturer’s data sheet.

》Line 8 to 10 show the results for 2A and 4A discharge currents. Both battery samples perform excellently without any overheating issues.

》Line 18 shows the discharge results at 9A. The first sample reaches 3780mAh, while the second sample does not complete the test. To maintain optimal performance, it’s best to avoid continuous discharge at high currents.

Conclusion

The XTAR 18650 battery, with a nominal capacity of 4000mAh, is a high-capacity protected battery. It can handle a maximum continuous discharge current of 8.5A to 9A, though overheating may occur at 10A. All test results meet the manufacturer’s specifications.

Currently, it leads in capacity among 18650 batteries and is ideal for users who require high capacity and safety. It is widely applicable for power banks, flashlights, portable measuring instruments, children’s toys and more.   

Thank you for following this test. See you next time!