How many years can lithium batteries generally last?
Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium-ion batteries. Lithium ion batteries do not contain metallic lithium and are rechargeable. The fifth generation product of rechargeable batteries, lithium metal batteries, was born in 1996. Its safety, specific capacity, self discharge rate, and cost-effectiveness are all superior to lithium-ion batteries. Due to its own high-tech requirements, only a few companies from countries are currently producing this type of lithium metal battery.
BATTERY LIFE
Can lithium-ion batteries only be charged and discharged 500 times?
I believe the vast majority of consumers have heard that the lifespan of lithium batteries is "500 times". After 500 charge and discharge cycles, the battery will "end its life". Many friends, in order to extend the lifespan of the battery, only charge it when the battery is completely depleted. Does this really have an effect on extending the lifespan of the battery? The answer is negative. The lifespan of a lithium battery is "500 times", which refers not to the number of times it is charged, but to one cycle of charging and discharging.
A charging cycle means the process of the battery's entire charge from full to empty, and then from empty to full, which is not equivalent to charging once. For example, a lithium battery only uses half of its capacity on the first day and then fully charges it. If it continues like this the next day, charging half of it and charging twice in total, this can only be considered as one charging cycle, not two. Therefore, it may usually take several charges to complete a cycle. After completing each charging cycle, the battery capacity will decrease slightly. However, the decrease in battery capacity is very small. High quality batteries can still retain 80% of their original capacity after multiple cycles of charging, and many lithium powered products can still be used as usual after two to three years. Of course, lithium batteries still need to be replaced at the end of their lifespan.
And the so-called 500 times refers to the manufacturer achieving about 625 rechargeable times at a constant discharge depth (such as 80%), reaching 500 charging cycles.
(80% * 625=500) (Ignoring factors such as reduced lithium battery capacity)
However, due to various influences in real life, especially the non constant discharge depth during charging, the "500 charging cycles" can only be used as a reference for battery life.
The correct statement is that the lifespan of lithium batteries is related to the number of charging cycles completed, not directly related to the number of charging cycles.
The lifespan of lithium batteries is generally 300-500 charging cycles. Assuming that the amount of electricity provided by a complete discharge is Q, without considering the decrease in electricity after each charging cycle, lithium batteries can provide or supplement a total of 300Q-500Q of electricity during their lifespan. From this, we know that if we charge with 1/2 each time, we can charge 600-1000 times; If it is charged every 1/3, it can be charged 900 to 1500 times. Similarly, if charged randomly, the number of times is not fixed. In short, no matter how it is charged, the total amount of electricity replenished is between 300Q and 500Q, which is constant. So, we can also understand it this way: the lifespan of lithium batteries is related to the total charging capacity of the battery, and not to the number of charging times. The impact of deep discharge and shallow charge on the lifespan of lithium batteries is not significantly different.
In fact, shallow discharge and shallow charge are more beneficial for lithium batteries, and deep discharge and deep charge are only necessary when the power module of the product is calibrated for lithium batteries. So, products powered by lithium batteries do not have to be limited by the process, everything is convenient first, can be charged at any time, and there is no need to worry about affecting their lifespan.
If lithium batteries are used in environments above the specified operating temperature of 35 ° C, the battery's charge will continuously decrease, meaning that the battery's power supply time will not be as long as usual. If the device needs to be charged at such a temperature, the damage to the battery will be even greater. Even storing batteries in hot environments will inevitably cause corresponding damage to the quality of the batteries. So, maintaining a suitable operating temperature as much as possible is a good way to extend the lifespan of lithium batteries.
If lithium batteries are used in low temperature environments, i.e. below 4 ° C, it will also be found that the battery life is reduced, and some phones' original lithium batteries cannot even be charged in low temperature environments. But don't worry too much, this is just a temporary situation. Unlike use in high-temperature environments, once the temperature rises, the molecules in the battery are heated and immediately restore their previous charge.
To maximize the efficiency of lithium-ion batteries, it is necessary to use them frequently to keep the electrons inside the battery in a flowing state. If you don't use lithium batteries frequently, please remember to complete a charging cycle and perform a power calibration once a month, that is, deep discharge and deep charge once.
The formal term is "charge discharge cycle", which does not equal "number of charges". A cycle refers to the process of a battery running from full charge to depletion, which is one cycle. If your battery uses one tenth of its capacity from full charge and then fully charges again, it is one tenth of a cycle. Charging it 10 times in this way is basically considered one cycle. Similarly, starting from fully charged, using half and then fully charged, and then using half and then fully charged again, this is also a cycle, at which point you have charged twice. So, the cycle only depends on how much electricity is accumulated from the battery, and is not directly related to the number of charging times.
Moreover, the nominal number of charge and discharge cycles does not mean that it cannot be used after being used up, but rather that after so many cycles, the battery's ability to store electricity will decrease to a certain extent,
For example, a certain lithium battery has a nominal charge and discharge cycle of "not less than 60% of the nominal capacity after 500 cycles"
After 500 cycles, this battery can only store up to 60% of its capacity as a new battery, indicating a certain degree of performance degradation.
There is no fixed limit on the number of charging times for lithium batteries. Batteries produced by regular manufacturers can generally be charged and discharged at least 500 times, and the capacity remains at 80% or more of the initial capacity. They can be used for 2 years with one charge per day. Usually, charging a mobile phone battery 1000 times can cause the battery to become severely unstable.
Maintenance methods for mobile phone batteries:
1. Each time it is fully charged, it reduces the number of charging times and improves the battery life.
2. You don't need to completely discharge the battery, usually when the battery level is below 10%, it needs to be charged.
3. Use the original charger for charging, do not use universal charging.
4. Do not use your phone during the charging process.
5. Do not overcharge, stop charging after the battery is fully charged.
Yes, according to the experimental results, the lifespan of lithium batteries decreases continuously with increasing charging times. Generally, lithium batteries are charged 2000-3000 times
Cycle is the use, we are using batteries, and what we care about is the duration of use. In order to measure the performance of rechargeable batteries in terms of how long they can last, we have defined the number of cycles. Actual user usage varies greatly, as experiments with different conditions cannot be compared. To make comparisons, it is necessary to standardize the definition of cycle life.
The test conditions and requirements for the cycle life of lithium batteries stipulated by the national standard: Under the condition of an ambient temperature of 20 ℃± 5 ℃, charge at 1C. When the terminal voltage of the battery reaches the charging limit voltage of 4.2V, switch to constant voltage charging until the charging current is less than or equal to 1/20C, stop charging, let it sit for 0.5h~1h, and then discharge at 1C current until the termination voltage is 2.75V. After the discharge is completed, let it sit for 0.5h~1h, and then proceed to the next charge and discharge cycle. If the continuous discharge time is less than 36min for two times, the life is considered terminated, and the number of cycles must be greater than 300.
Interpretation of national standard regulations:
A. This definition stipulates that the testing of cycle life is conducted through deep charging and discharging methods
B. The cycle life of lithium batteries is specified according to this mode, and after ≥ 300 cycles, the capacity still exceeds 60%
However, the number of cycles obtained from different cycle systems is completely different. For example, keeping all other conditions unchanged, only changing the constant voltage of 4.2V to 4.1V to test the cycle life of the same model of battery is no longer a deep charging method. In the end, the test showed that the cycle life can be increased by nearly 60%. So if the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased several times.
The statement that one cycle of charging and discharging reduces the lifespan of a lithium battery should be noted that the definition of the charging cycle of a lithium battery is: one charging cycle refers to the process of the battery's entire charge from full to empty, and then from empty to full. And this is not equivalent to charging once. In addition, when discussing the number of cycles, we cannot ignore the conditions of the cycle. It is meaningless to talk about the number of cycles without considering the rules, because the number of cycles is a means of detecting battery life, not the goal!
