18650 battery 3500mah lithium

　　How to judge whether the 18650 battery 3500mah lithium is good or bad?

　　To judge the quality of a 18650 battery 3500mah lithium, you can measure it from the aspects of appearance, load measurement, multimeter measurement, etc.; common faults include uneven floating charge voltage, battery bulging and deformation, battery leakage, etc. The following is a detailed introduction to "How to judge UPS batteries" Good, Bad and Common Faults”.

　　1. How to judge the quality of 18650 battery 3500mah lithium

　　1. Judging from appearance

　　Observe the appearance for deformation, protrusions, leakage, cracks, explosions, burns, and oxide seepage at screw connections.

　　2. Load measurement

　　If there is no abnormality in appearance, the UPS is operating in battery mode with a certain amount of load. If the discharge time is significantly shorter than the normal discharge time and the normal backup time cannot be restored after 8 hours of charging, the battery is judged to be aging.

　　3. Measure with a multimeter

　　①Measurement in battery discharge mode

　　Measure the voltage of each battery terminal in the battery pack. If the voltage of one or more battery terminals is significantly higher or lower than the nominal voltage (nominal voltage 12V/cell), judge the battery aging.

　　②Measurement in mains power mode

　　The charging voltage of each battery terminal in the battery pack. If the charging voltage of one or more batteries is significantly higher or lower than other voltages, the battery is judged to be aging.

　　③Measure the total voltage of the battery pack

　　The total voltage of the battery pack is significantly lower than the nominal value. It cannot return to the normal value after 8 hours of charging. Even if it returns to the normal value, the discharge time cannot reach the normal discharge time, and the battery is judged to be aging.

　　④Battery power-on measurement

　　Do not turn on the UPS, and do not connect it to the mains. First use a multimeter to measure the total voltage of the battery pack. Do not leave the test leads. Keep an eye on the multimeter's instructions, and then connect the power button. If the total battery voltage immediately drops below 30V or even more than ten volts, , the UPS automatically shuts down immediately, and the voltage returns to its original value immediately after shutting down. Determine battery aging.

　　2. Common faults of UPS batteries

　　1. Unbalanced floating charge voltage

　　Valve-regulated lead-acid batteries commonly have problems with uneven float voltage and open circuit voltage deviation. The uniformity of a valve-regulated lead-acid battery refers to the difference between the open circuit voltage measured after the battery is completed and the float voltage of the battery pack in the float state. Relevant standards stipulate that the difference in the open circuit voltage of each single cell in the battery pack shall not be greater than 20mV, and the difference in the float charge voltage of each single cell in the float charge state shall not be greater than 100mV. If there is a voltage deviation in the battery pack, it will cause early failure of the lagging battery.

　　2. Battery bulging and deformation

　　This is a very destructive phenomenon that occurs when valve-regulated lead-acid batteries are used improperly, that is, thermal runaway, which can cause the battery tank to bulge and deform, accelerate water loss, and even damage the battery.

　　3. Battery leakage

　　Valve-regulated lead-acid batteries will have leakage problems to varying degrees, mainly in battery tank cover leakage, safety valve leakage, and pole terminal leakage.

　　4. Battery loses water

　　Valve-regulated lead-acid batteries work in a "lean" state, and their electrolyte is completely stored in the porous AGM diaphragm. Once the battery loses water, it will cause the positive and negative electrodes of the battery to come out of contact with the electrolyte in the separator, causing the battery to be unable to discharge electricity. The use results show that most of the current reasons for the decline in the capacity of valve-regulated lead-acid batteries are caused by battery water loss. When the water loss reaches 3.5ml/Ah, the battery capacity will drop to less than 75% of the initial capacity; when the water loss reaches 25%, the battery life will be terminated.

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