What factors affect the life of lithium batteries?

Lithium batteries are generally capable of charging and discharging 300-500 times. It is better to partially discharge the lithium battery instead of completely discharging it, and try to avoid frequent full discharging. Once the battery is off the production line, the clock begins to move. Whether you use it or not, the life of a lithium battery is only in the first few years. The decrease in battery capacity is due to an increase in internal resistance caused by oxidation (this is the main cause of battery capacity degradation). Finally, the cell resistance will reach a certain point, although the battery is fully charged, the battery will not release the stored charge.

The aging speed of a lithium battery is determined by temperature and state of charge. The table below shows the reduction in battery capacity for both parameters.

Temperature charging 40% charging 100%

0°C capacity after one year 98% capacity 94% after one year

25 ° C after one year capacity 96% after a year capacity 80%

40°C capacity after 8 years, capacity is 65% after one year

After 60°C, the capacity is 75% after one year, and the capacity is 60% after three months.

As can be seen from the above, the high state of charge and the increased temperature accelerate the decline in battery capacity.

If possible, try to charge the battery to 40% in a cool place. This allows the battery own protection circuit to operate during long periods of storage. If the battery is placed at a high temperature after being fully charged, it will cause great damage to the battery. (So when we use a fixed power supply, the battery is fully charged at this time, the temperature is usually between 25-30 ° C, which will damage the battery, causing its capacity to drop).

Influencing factor

1: Depth of discharge and number of chargeable times

The left graph data obtained from the experiment can be known that the number of chargeable times is related to the depth of discharge, and the deeper the battery discharge depth, the less the number of chargeable times.

Rechargeable times*Discharge depth=Total number of completions of the total charge cycle. The higher the total number of charge cycle completions, the higher the life of the battery, the number of charge cycles* the depth of discharge=the actual battery life (ignoring other factors)

2: Overcharge, over discharge, and large charge and discharge currents

Avoid overcharging the battery. Any form of overcharging of the lithium-ion battery can cause serious damage to the battery performance and even explosion.

Avoid deep discharges below 2V or 2.5V as this will 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 circuitry inside the battery pack that disconnects the battery if the battery voltage drops below 2.5V, exceeds 4.3V when charging or discharging, or if the battery current exceeds a predetermined threshold.

Avoid large charging and discharging currents because large currents put excessive pressure on the battery.

3: Overheated or too cold environment

Temperature also has a large impact on the life of lithium batteries. The environment below the freezing point may cause the lithium battery to burn out at the moment when the electronic product is turned on, and the overheated environment will reduce the capacity of the battery. Therefore, if the notebook does not take off the battery after long-term use of the external power supply, the battery will be in the high heat of the notebook for a long time, and will soon be scrapped.

4: Full power, no power for a long time

Excessively high and too low state of charge adversely affects the life of the lithium battery. Most resellers that are sold on appliances or batteries are recharged based on 80% discharge. Experiments have shown that for some laptop lithium batteries, the battery voltage often exceeds the standard voltage of 0.1 volts, that is, from 4.1 volts to 4.2 volts, then the battery life will be halved, and then increased by 0.1 volts, the life is reduced to the original 1 /3; The more fully charged the battery, the greater the loss of the battery. A long-term low-power or no-power state will cause the internal resistance of the battery to move more and more, resulting in a smaller battery capacity. The lithium battery is preferably in the middle of the battery, so that the battery life is the longest.

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