Discussion on solutions to 18650 battery 3.7v 2200mahperformance degradation problem

　　High self-discharge rate

　　All kinds of batteries have self-discharge, but improper use will promote the development of this state. The self-discharge rate follows an asymptote law. The highest discharge rate appears just after charging, and then gradually decreases.

　　Nickel-based batteries exhibit higher self-discharge rates. Under normal ambient temperatures, the charge capacity of a new nickel-cadmium 18650 battery 3.7v 2200mahwill be reduced by approximately 10% during the first 24 hours after charging. Thereafter, the self-discharge rate stabilized to approximately 10% per month. Usually at higher temperatures, the discharge rate also increases. The general guideline is: the self-discharge rate doubles for every 10°C increase in temperature. The self-discharge rate of nickel metal hydride batteries is approximately 30% greater than that of nickel-cadmium batteries.

　　The self-discharge rate of nickel-based batteries also increases after hundreds of cycles. The plates of the 18650 battery 3.7v 2200mahbegin to expand and squeeze the separator between the electrodes more tightly, forming metal dendrites. This is the result of crystal growth (memory effect ), thus damaging the 18650 battery 3.7v 2200mahseparator and increasing the self-discharge rate. If the self-discharge of nickel-based batteries reaches 30% in 24 hours, they should be discarded.

　　The self-discharge rate of nickel-ion batteries in the first 24 hours after charging is 5%. It has since dropped to 1%-2% per month, and the battery's safety protection circuit has increased by about 3%. High cycle times and aging have no effect on the self-discharge rate of lithium-based batteries. The self-discharge rate of lead-acid batteries is about 5% per month or 50% per year. Repeated deep cycle charge and discharge will increase the self-discharge.

　　The percentage of 18650 battery 3.7v 2200mahself-discharge can be measured with a 18650 battery 3.7v 2200mahanalyzer, but this procedure takes several hours. The measured internal resistance of the 18650 battery 3.7v 2200mahcan often reflect whether the internal resistance of the 18650 battery 3.7v 2200mahis too high. This parameter can be measured with an impedance meter or using the ohm test program of a 18650 battery 3.7v 2200mahanalyzer.

　　18650 battery 3.7v 2200mahmatching

　　Even with modern manufacturing techniques, 18650 battery 3.7v 2200mahcapacity is impossible to accurately predict, especially for nickel-based batteries. During the manufacturing process, each 18650 battery 3.7v 2200mahis inspected and classified according to its capacity. High-capacity Category "A" batteries are typically sold as special-purpose batteries at premium-grade prices; mid-capacity Category "B" batteries are used in industrial and commercial products; and low-end Category "C" batteries are sold at bargain prices. The capacity of low-end category batteries cannot be improved by cycling charge and discharge. What you get when you buy low-priced rechargeable batteries is low 18650 battery 3.7v 2200mahcapacity.

　　In a 18650 battery 3.7v 2200mahpack composed of multiple cells, the matching of cells should be controlled within ±2.5%. In 18650 battery 3.7v 2200mahpacks with a large number of cells, as well as 18650 battery 3.7v 2200mahpacks that need to output large load currents and operate at low temperatures, stricter 18650 battery 3.7v 2200mahtolerance control is required. If there is a slight mismatch between the individual cells in a new 18650 battery 3.7v 2200mahpack, they will be able to balance each other and adapt themselves after several charging cycles. Whether the batteries can be well balanced and adapted to each other is related to whether the 18650 battery 3.7v 2200mahpack has a long service life.

　　Why is 18650 battery 3.7v 2200mahmatching so important? This is because a "weak" 18650 battery 3.7v 2200mahcontains less capacity, which discharges and recharges faster than a "strong" battery. This imbalance in the discharge process causes "weak" batteries to reverse polarity as they discharge past low voltages. When charging, the "weak" 18650 battery 3.7v 2200mahfirst enters the overcharge state of heat during the charging process, while the stronger 18650 battery 3.7v 2200mahcan still accept charging normally without generating heat. In both cases the "weak" 18650 battery 3.7v 2200mahis in an unfavorable condition, making it even "weaker" and causing severe mismatches. High-quality batteries have a more consistent and balanced capacity than low-quality batteries. High-quality batteries should be used for high-end high-power tools because they have high durability under heavy loads and extreme temperature environments. Although the cost is high, the reward is a longer life of the 18650 battery 3.7v 2200mahpack.

　　Lithium-based batteries are well matched to their intrinsic properties as they come off the production line. It is very important that the individual cells within the 18650 battery 3.7v 2200mahpack meet strict tolerances. All cells in the 18650 battery 3.7v 2200mahpack must be fully charged within the same time and reach the same threshold voltage at the end of discharge. The built-in protection circuit of the 18650 battery 3.7v 2200mahpack should provide safety protection when the 18650 battery 3.7v 2200mahis in abnormal working conditions.

　　Shorted battery

　　18650 battery 3.7v 2200mahmanufacturers often cannot explain why some batteries display high leakage rates or develop electrical shorts when the batteries are still new. The suspected reason is that foreign particles may have been mixed into the 18650 battery 3.7v 2200mahduring the manufacturing process. The other is that rough spots on the electrode cause damage to the diaphragm. Therefore, the manufacturing process of batteries should be improved, which can greatly reduce the "infantmortality" of batteries.

　　Reversing the battery's polarity due to deep discharge can also cause the 18650 battery 3.7v 2200mahto short circuit. This state may also occur if the nickel-based 18650 battery 3.7v 2200mahis discharged at high current until it is completely discharged. High reverse current can cause a permanent electrical short circuit. Another cause is damage to the septum caused by uncontrolled lens formation, which is the so-called memory effect.

　　Using instantaneous high-current pulses to try to repair a short-circuited 18650 battery 3.7v 2200mahhas a very limited success rate. This short circuit may be temporarily evaporated, but the damage to the diaphragm material remains. Such repaired batteries often exhibit high discharge rates and the short circuit recurs. It is not advisable to replace a shorted cell in an aged 18650 battery 3.7v 2200mahpack. Unless the new 18650 battery 3.7v 2200mahmatches the performance of the other batteries in the pack in terms of 18650 battery 3.7v 2200mahvoltage and capacity.

　　Loss of electrolyte

　　Batteries, although sealed, will lose some electrolyte during their service life, especially if outgassing occurs due to excessive gas pressure due to careless improper charging. Once outgassing occurs, the spring-loaded vent seal on the nickel-based 18650 battery 3.7v 2200mahmay be difficult to reseal intact, causing white powder to deposit around the seal. The loss of electrolyte will eventually reduce the 18650 battery 3.7v 2200mahcapacity.

　　Leakage, or loss of electrolyte in valve-regulated lead-acid batteries (VRCA), is a long-standing problem. The reasons are caused by overcharging and working at high temperatures. The effect of adding water to replenish the electrolyte loss is limited. Although the 18650 battery 3.7v 2200mahcapacity can be partially restored, the 18650 battery 3.7v 2200mahperformance will be unreliable.

　　If charged correctly, lithium-ion batteries should not produce gases that would cause outgassing problems. But lithium-ion batteries can also develop internal stress under certain conditions. Some batteries have internal circuit switches that cut off the flow of electricity when the 18650 battery 3.7v 2200mahpressure reaches a certain threshold. Other batteries are designed to release gas in a controlled manner or by opening the safety diaphragm.

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