Assessing the quality of 18650 lithium batteries is crucial, especially when using or purchasing them. Here are some common methods and indicators that can help you determine the quality of an 18650 lithium battery:

　　Voltage Measurement: Use a digital multimeter or voltmeter to measure the battery's voltage. A fully charged 18650 battery should typically fall within its rated voltage range, usually between 3.6V to 4.2V. If the voltage is significantly lower than this range, it may indicate battery damage or over-discharge.

　　Capacity Testing: Employ professional battery testing equipment to measure the battery's capacity. A properly functioning 18650 battery should approach or meet its nominal capacity. A capacity far below the rated value could indicate battery aging or damage.

　　Visual Inspection: Carefully examine the battery's exterior to ensure there are no physical damages, dents, leaks, or deformities. Any of these signs might indicate battery damage or safety issues.

　　Charging and Discharging Testing: Fully charge the battery and place it in a suitable device to test its performance during use. Observe if the battery functions normally, provides continuous power, or exhibits any abnormal heating.

　　Rebound Test: Gently tap the battery; a good 18650 battery should not produce noticeable vibration sounds, indicating that its internal components are secure.

　　Brand and Supplier: Purchase batteries from reputable brands and suppliers to increase the likelihood of acquiring high-quality batteries.

　　Please note that assessing the quality of 18650 lithium batteries can be relatively complex and may sometimes require specialized testing equipment and expertise. If you are uncertain or unfamiliar with battery assessment, seek assistance from professionals. Also, if you notice any abnormalities or safety concerns with the battery, discontinue its use immediately and handle it safely.