Lithium Battery Using Method

- Apr 28, 2018-

For the “activation” problem of newly-purchased lithium-ion batteries, many arguments are: The charging time must be more than 12 hours, repeated three times in order to activate the battery. This statement that "the first three charges must be charged for more than 12 hours" is obviously a continuation of nickel batteries (such as nickel-cadmium and nickel-hydrogen). Therefore, this argument can be said to be misinformation at the beginning. The charging and discharging characteristics of lithium batteries and nickel batteries are very different, and it can be clearly stated that all serious formal technical data emphasizes that overcharging and overdischarging will cause huge impact on lithium batteries, especially liquid lithium-ion batteries. hurt. Therefore, it is best to charge in accordance with the standard time and standard methods, in particular, do not charge more than 12 hours.

Does the battery need to be activated? The answer is yes, need to activate! However, this process is completed by the manufacturer, has nothing to do with the user, the user does not have the ability to complete. The actual activation process of a lithium battery is such that the lithium-ion battery case is filled with an electrolyte--seal--formation, that is, charged at a constant voltage and then discharged, so that several cycles are performed so that the electrode is fully infiltrated with the electrolyte and fully activated until the capacity reaches So far, this is the activation process - the demarcation, that means the lithium-ion battery has been activated to the user's hand after delivery. In addition, some of the battery activation process requires the battery to be in an open state, and then seal it after activation, unless you have a battery production device, how to complete?

However, why do some products' manuals say that it is recommended that users use the device three times before, and that it should be completely charged and discharged? Is this not activation? Actually, the fact is that when the battery is shipped from the factory and then sold to the user's hands, it will go through a period of time, a month or a few months. In this way, the electrode material of the battery will be “passivated” and the capacity is low at this time. At normal values, the use time is also shortened. However, the lithium battery is very easy to activate, as long as 3 to 5 normal charge and discharge cycles can activate the battery and restore normal capacity. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the user's new lithium battery does not require special methods and equipment during the activation process.

The danger of long charge and deep charge

Long time charge may result in overcharge. Lithium batteries or chargers automatically stop charging when the battery is full, and there is no so-called "trickle" charging of the nickel charger for 10 hours. In other words, if your lithium battery is full, it's white charger. And no one of us can guarantee that the characteristics of the battery's charge and discharge protection circuit will never change and the quality will be absolutely safe, so your battery will be in danger for a long time. This is another reason why we oppose long charge.

On some machines, if the charger is not removed after charging for more than a certain period of time, the system will not only stop charging but will also start the discharge-charge cycle. Perhaps the manufacturer of this practice has its own purpose, but it is obviously unfavorable for the life of the battery. At the same time, long charging takes a long time and often needs to be carried out at night. According to the situation of China's power grid, the voltage at night in many places is relatively high and fluctuates. As already mentioned, the lithium battery is very delicate. It is much less tolerant to the fluctuations in charge and discharge characteristics of nickel electricity, and this brings additional danger.

In fact, shallow shallow charge is more beneficial to lithium battery. Only when the power module of the product is calibrated for lithium battery is it necessary to deep-charge deep charge. Therefore, the use of lithium-powered products does not have to be rigidly adhered to the process, everything is convenient and always charged.

Overcharge, overdischarge hazards

The rated voltage of a lithium-ion battery is generally 3.7V due to recent material changes, and the lithium iron phosphate (hereinafter referred to as ferrophosphorus) positive electrode is 3.2V. When fully charged, the termination charge voltage is typically 4.2V, phosphorous iron 3.65V. Lithium-ion battery termination voltage is 2.75V ~ 3.0V (battery plant gives the operating voltage range or given the discharge voltage, each parameter is slightly different, usually 3.0V, ferrosilicon is 2.5V). Below 2.5V (ferrosilicon 2.0V), continuous discharge is called overdischarge. Low-voltage overdischarge or self-discharge reaction will lead to decomposition and destruction of lithium-ion active material, which cannot be reduced. The overcharge of lithium ion battery in any form will cause the battery performance to be seriously damaged or even exploded. Lithium-ion batteries must avoid overcharging the battery during charging.

Battery Life Related Knowledge Reference Battery Life

Lithium-ion battery can only charge and discharge 500 times?

I believe most consumers have heard that lithium battery life is "500 times", 500 times charge and discharge, more than this number, the battery "end of life", and many friends in order to be able to extend the life of the battery, each time Is the battery charged only when it is fully depleted, does this really extend the life of the battery? the answer is negative. Lithium battery life is "500 times", not referring to the number of charges, but a charge and discharge cycle.

A charge cycle means that the battery's full charge to empty, and then empty to full, is not the same as charging a battery. For example, a piece of lithium used only half of the electricity on the first day, and then it was fully charged. If this is the case on the second day, it will be charged in half and charged twice in total. This can only be counted as one charge cycle, not two. Therefore, it may take several times to complete a cycle. Each time a charge cycle is completed, the battery capacity is reduced by a little. However, the amount of power reduction is very small. After a high-quality battery has been charged for many cycles, it will still retain 80% of the original capacity. Many lithium-powered products are still used after two to three years. Of course, the lithium battery life still needs to be replaced after the end.

The so-called 500 times means that the manufacturer has achieved about 625 times of recharge times at a constant discharge depth (such as 80%) and reached 500 charging cycles.

(80% * 625 = 500) (ignoring lithium battery capacity and other factors)

Due to various effects of real life, especially the depth of discharge during charging is not constant, the '500 charge cycles' can only serve as a reference battery life.

Life and influencing factors

Lithium batteries can generally charge and discharge 300-500 times. It is best to partially discharge the lithium battery instead of fully discharging, and try to avoid frequent full discharge. Once the battery goes down the production line, the clock starts to move. Regardless of whether you use or not, the service life of lithium batteries is only in the first few years. The decrease in battery capacity is due to an increase in the internal resistance caused by oxidation (which is the main cause of the decrease in battery capacity). Finally, the cell resistance will reach a certain point, although the battery is fully charged at this time, but the battery can not release the stored power.

Lithium battery aging rate is determined by the temperature and state of charge. The following table shows the reduction in battery capacity under both parameters.

Temperature charge 40% charge 100%

After 0°C One year capacity 98% One year capacity 94%

Capacity after 96% at 25°C Capacity 80% after one year

Capacity after 8 years at 40°C Capacity 65% after one year

Capacity after 70% at 60°C Capacity 60% after 3 months

If possible, try to charge the battery to 40% in a cool place. This allows the battery's own protection circuit to operate for a long period of storage. If the battery is left at a high temperature after it is 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 generally between 25-30 °C, which will damage the battery, causing its capacity to drop).

Influencing factor 1: depth of discharge and number of chargeable

From the left data of the experiment, it can be known that the number of chargeable times is related to the depth of discharge, and the deeper the depth of discharge of the battery, the less chargeable times.

Rechargeable times * Discharge depth = total number of charge cycles completed, the higher the total number of charge cycles completed, the higher the battery life, the number of chargeable times * depth of discharge = actual battery life (ignoring other factors)

Influencing factors 2: overcharge, overdischarge, and large charge and discharge currents

To avoid overcharging the battery, any overcharge of the lithium ion battery can cause the battery performance to be seriously damaged or even explode.

Avoid deep discharges below 2V or 2.5V, as this will quickly and permanently damage the Li-Ion battery. Internal metal plating may occur, which can cause a short circuit, making the battery unusable or unsafe.

Most Li-Ion batteries have electronic circuitry inside the battery pack. If the battery voltage drops below 2.5V, exceeds 4.3V when the battery is charged or discharged, or if the battery current exceeds a predetermined threshold, the electronic circuit will disconnect the battery.

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

Influencing factor 3: Overheated or undercooled environment

Temperature also has a greater impact on the life of lithium batteries. Below the freezing point, the lithium battery may burn out when the electronic product is turned on, and the overheated environment will reduce the battery capacity. Therefore, if the notebook does not use the external power supply for a long time and the battery is removed, the battery will remain in the high fever of the notebook for a long time and will be scrapped soon.

Influencing factors 4: Long-term power, no power state

Excessively high and low battery conditions adversely affect the life of a lithium battery. The number of recharges that can be marked on most appliances or batteries is based on a discharge of 80%. 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 1 /3; The more full the battery is charged, the greater the loss of the battery. The long-term low-battery or no-battery condition will cause more and more resistance to the movement of electrons inside the battery, resulting in a decrease in battery capacity. Lithium batteries are best in the middle of the battery, so that the battery life is the longest.

From the above, it can be concluded that the following points can extend the lithium battery capacity and life precautions.

1. If you are using an external power supply to power the notebook for a long period of time, or if the battery power has exceeded 80%, remove the battery immediately. Usually charge without charging the battery, charge it to 80% or so. Adjust the operating system's power options to adjust the battery alarm to more than 20%, and normally do not lower the battery power below 20%.

2. Small electronic devices such as mobile phones should be immediately disconnected from the power cord (including the USB port for charging function) when they are charged. Connecting them will damage the battery. Always charge, but you do not have to charge the battery.

3. Be sure not to run out of battery (automatic shutdown) for laptops or mobile phones.

4. If you are traveling, charge the battery, but charge the appliance at any time if conditions allow.

5. Use smarter power-saving operating systems.

In summary, the most important tips for the charge and discharge problems of lithium batteries in use are:

1. Charging according to standard time and procedures, even if it is a new lithium battery, it must be done in the first three times;

2. When the low battery indicator appears, you should start charging as soon as possible (don't wait for automatic shutdown);

3. Lithium battery activation does not require special methods, in the normal use of the lithium battery will be naturally activated. If you insist on using the popular "first three 12-hour charge" activation method, it will not actually work.

Therefore, all pursuing the 12-hour long charging and the use of a single-cell lithium battery for automatic shutdown are all wrong. If you used to do it in the wrong way, please correct it in time. It may not be too late.