Review of the XTAR 18650 3500mAh Protected Battery

Jun 03, 2024 | XTAR

Today, I’ll be giving you an overview of the new XTAR 18650 Protected Lithium-ion Battery. This battery model has a declared capacity of 3500mAh and comes with a built-in protection board for added safety.

Overview and Specifications

Here are the key specifications of this battery:

  • Nominal Capacity: 3500mAh
  • Minimum Capacity: 3325mAh
  • Nominal Voltage: 3.6V
  • Lower Discharge Threshold: 2.5V
  • Maximum Continuous Discharge Current: 10A
  • Internal Resistance: ≤ 45mΩ
  • Battery Life: 800 cycles
  • Operating Temperature: -20°C to 60°C

The battery is supplied in cardboard boxes. Each battery is individually packaged with shrink film, featuring white and blue lettering on the positive terminal. The energy capacity is 12.6 watt-hours, with a resource of over 800 charge-discharge cycles. 

Additionally, the battery has a built-in protection board to safeguard against overcharging and over-discharging.

Notably, the battery’s production date was not indicated on the case, but it was confirmed to be freshly manufactured in 2024. The battery weighed approximately 48g. I compared the weight of the two samples. The first sample was 47.66g, and the second sample was slightly heavier at 47.73g.

Both of the two samples had dimensions typical of a size 18650 battery, with a length of 69.1mm. Due to the protection board, it’s slightly longer than standard 18650 batteries, adding about 4-5mm to its length. 

The internal battery resistance, tested at a frequency of 1kHz, aligned closely with the declared value of ≤45mΩ, with real values measuring 27.5mΩ and 27.6mΩ. Similarly, the average equivalent series resistance at a discharge current of 700mA closely matched the declared value. 

Performance Test

The test was conducted using an industrial-grade chemical current source analyzer – ACK, with a discharge current of 700mA to a cutoff discharge voltage of 2.5V. After a one-hour pause, charging began at 700mA until the upper voltage threshold of 4.2V was reached. This was followed by another one-hour pause and then a discharge at 700mA, totaling nearly 14 hours of testing. 

1. Discharge Performance

I generated a graph to see the battery discharge curve at currents ranging from 700mA to 10A. The graph shows voltage on the vertical axis and charge amount in ampere-hour on the horizontal axis.

it must be said that even with maximum declared discharge current 10 A, the amount of charge given was higher than 3.3 Ah.

2. Protection Test

After careful consideration, I opted to discharge the battery gradually until it reached the lower voltage threshold, prompting the protection board to activate. At a discharge current of 500mA, the protection board was triggered when the voltage dropped to 2.498V. Conversely, during a discharge with a current of 10A, the protection board was triggered at a voltage value of 2.343V. 

3. Temperature Test

Surface temperature indicators were monitored during testing.

When discharged with a current of 3.5 A, the battery heated up to 38 degrees. At current 7 A, it was up to 54°C. And at a current of 10 A, the heating was, at moment of completion of testing, 67.68°C. The board protection did not work due to such heating. That is, the discharge was up to the Lower threshold voltage 2.5 V, heating up to 67°C. Well, there is nothing critical. But in my opinion, if you want to extend the service period of your batteries, it is better avoid high currents.

4. Real Capacity Test

The testing results were presented below, with indicators assessing the battery’s characteristics. The second column displayed these indicators, followed by specifications in the third column, test results in the fourth and fifth columns, and surface temperature indicators in the sixth column. 

When discharged with a current of 700 mA to the lower voltage threshold 2.5 V, the battery capacity at declared minimum value 3325 and nominal 3500 mAh. The real values of the two samples were 3494 and 3489 mAh, almost equal to the upper nominal value that manufacturer indicated. The battery capacity was rated honest.

At seventh line, energy capacity of batteries at declared value from 12 to 12.6 Watt hours, and the real value turned out to be 12.5 watt hour.

In twelfth line, at discharge current 7 A, the declared value manufacturer given 3,394 mAh. In my test result, the first sample was given 3393mAh, and second 3379 mAh. The values are very close.

At higher discharge current 10 A, the battery capacity of the first sample gave 3335mAh and the second 3323 mAh, also closely approximated the manufacturer’s specifications. These official test data can be found in their data sheet.  


In summary, the testing results validate the manufacturer’s specifications for the XTAR 18650 Protected Lithium-ion Battery. With a declared capacity of 3,500mAh, it boasts high capacity and energy efficiency. It can handle a maximum continuous discharge current of 7A, with an allowable discharge current of 10A and temperature cutoff control at 60°C.

With its protective features and high capacity, this battery is suitable for a wide range of consumer applications, including power banks, portable measuring devices, lamps, and children’s toys. However, users should note that due to its protection board, the battery is longer than standard 18650 batteries by approximately 5mm, necessitating compatibility checks before purchase.

For a detailed demonstration and more insights, watch the full review video here.


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