What are the factors that affect the life of lithium battery?

Battery life

Lithium-ion batteries can only be charged and discharged 500 times?

Believe that the vast majority of consumers have heard that the life of lithium battery is "500 times", 500 charge and discharge, more than this number, the battery is "dead", many friends in order to be able to extend the life of the battery, every time in the battery completely exhausted when charging, so really extend the effect of battery life?The answer is no.The life of a lithium battery is "500 times", which refers not to the number of charges, but a cycle of charge and discharge.

A charging cycle means that all the power of the battery is used from full to empty, and then from empty to full process, which is not equivalent to a single charge.For example, a piece of lithium battery only uses half of its electricity on the first day, and then fully charges it.If it's so the next day, just half, two times, which can only count as a charging cycle, not two.Therefore, it may usually take charging several times to complete a cycle.For each charging cycle completed, the battery capacity decreases a little bit.However, the reduction is very small, with high-quality batteries retaining 80% of their original capacity after multiple cycles, and many lithium power supply products are still used as usual after two or three years.Of course, the lithium battery life is still the need to be replaced after the end.

The so-called 500 times, refers to the manufacturer in a constant discharge depth (such as 80%) to achieve about 625 charging times, reaching 500 charging cycles.

(80% * 625=500) (ignoring factors such as reduction of lithium battery capacity)

Due to the various effects of real life, especially the discharge depth when charging is not constant, so & quot; 500 charging cycle & quot; can only be used as a reference battery life.

influencing factor

Lithium-ion batteries can usually be charged for another 300-500 times.It is best to partially discharge lithium batteries, rather than complete discharge, and try to avoid frequent complete discharge.Once the battery is off the line, the clock started around.Whether you use it or not, lithium battery life last in the first few years.The decrease in battery capacity is due to increased internal resistance from oxidation (the main cause of the decline in battery capacity).Finally, the cell resistance reaches a certain point, and although the battery is fully charged, the battery cannot release the stored power.

The aging speed of lithium batteries is determined by the temperature and charging state.The following table illustrates the reduction in the battery capacity under the two parameters.

As can be seen from Figure 1, the high charging state and the increased temperature accelerate the decline of the battery capacity.

If possible, try to charge the battery to 40% in a cool place.This allows the protection circuit of the battery itself to operate over a long period of storage.If the battery is placed at a high temperature when fully charged, it can cause great damage to the battery.(So when we use a fixed power supply, the battery is full and the temperature is usually between 25 and 30°C, which will damage the battery and cause its capacity to drop.)

Influencing factor 1: discharge depth and rechargeable times

The data obtained from the experiment shows that the number of rechargeable times is related to the discharge depth, and the deeper the battery discharge depth, the less the number of rechargeable times.

Charging times * discharge depth = total charging cycle completion times, the higher the total charging cycle completion times, the higher the battery life, charging times * discharge depth = actual battery life (ignoring other factors)

Influencing factor 2: overcharge, overdischarge, and large charging and discharge current

Avoid overcharging of the battery, any form of lithium-ion battery will lead to serious battery performance damage, or even explosion.

Avoid deep discharges of less than 2V or 2.5V, as this can quickly and permanently damage the lithium-ion battery.Internal metal plating may occur, which can cause a short circuit and make the battery unusable or unsafe.

Most lithium-ion batteries have electronic circuits inside the battery pack that disconnect if the battery voltage is below 2.5V or above 4.3V when charging or discharging, or if the battery current exceeds the predetermined threshold.

Avoid large charging and discharge currents, which put too much pressure on the battery.

Impact actor 3: overheating or too cold environment

Temperature also has a great impact on the life of lithium battery.Below freezing temperatures can cause lithium batteries to burn down when electronics turn on, while overheated environments can reduce their capacity.Therefore, if the notebook uses the external power supply for a long time and does not take off the battery, the battery will be in the high heat discharged by the notebook for a long time, and will soon be scrapped.

Influencing factor 4: long time full power, no power state

Too high and too low power state have a negative impact on the life of lithium battery.Most of the recurring charging times identified on selling appliances or batteries are based on 80% discharge.Experiments show that for some laptop lithium battery, often let the battery voltage above the standard voltage 0.1 volts, that is, from 4.1 volt to 4.2 volts, then the battery life will be halved, and then increase 0.1 volts, the life is reduced to the original 1 / 3; the more charged the battery, the greater the battery loss will be.Long-term low or no power will increase the resistance to the movement of the battery, resulting in smaller battery capacity.Lithium-ion batteries are preferably in the middle of the battery, with the longest battery life.