What exactly is the right way to use lithium batteries?

Note 1: Lithium-ion battery storage

Lithium-ion batteries can be stored in clean, dry and ventilated rooms with an ambient temperature of -5 ° C - 35 ° C and a relative humidity of not more than 75%. Avoid contact with corrosive substances and keep away from fire and heat sources. Battery power is maintained at 30% to 50% of nominal capacity. The recommended storage battery is charged every 6 months.

Note 2, Lithium-ion battery charging

To charge a Li-Ion battery, use a dedicated Li-Ion battery charger.

Lithium-ion battery charging adopts CC/CV mode (constant current + constant voltage), that is to say, charging with a constant current first, when the voltage reaches 4.2V*n, it is converted to constant voltage charging until the current is reduced to 0.01C.

Note 3: Lithium-ion battery is fully stored and then stored, which can reduce the capacity loss.

This idea is a big mistake. Lithium-ion batteries are different from nickel-chromium and nickel-metal hydride batteries because they have a very bad "aging" characteristic, that is, after storage for a period of time, even if it is not recycled, its partial capacity. It will also be permanently lost. The reason is that the positive and negative materials of the battery have already started its depletion process since leaving the factory. The speed of "aging" varies with different temperatures and different states of charge.

Storage temperature state

Store after storage at 100% saturation after 40% saturation

0% left 98% (after one year) 94% left (one year later)

96% left after 25oC (after one year) 80% left (one year later)

85% left after 40oC (after one year) 65% left (one year later)

60% remaining at 60oC (after one year) 60% remaining (after 3 months)

Lithium batteries have no memory effect, so you can charge them at any time.

Caution: When using lithium cell should be noted that the period of time after the battery is placed into hibernation, lower than normal capacity at this time, use of time will also be shortened. However, the lithium battery is easy to activate, as long as the battery is activated after 3 to 5 normal charge and discharge cycles, and the normal capacity is restored. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the new lithium battery in the user's mobile phone does not require special methods and equipment during the activation process. Not only in theory, but from my own practice, it is best to use a standard method of charging this "natural activation" method from the beginning.

For the "activation" problem of lithium batteries, there are many sayings: charging time must be more than 12 hours, repeated three times in order to activate the battery. This statement that "the first three charges have to be charged for more than 12 hours" is obviously a continuation of nickel batteries (such as nickel cadmium and nickel hydride). So this kind of statement can be said to be misinformation at the beginning. The charge and discharge characteristics of lithium and nickel batteries are very different, and it is very clear to tell you that all the serious formal technical information I have reviewed emphasizes that overcharge and over discharge will make lithium batteries, especially liquid lithium. Ion batteries cause great damage. Therefore, charging is preferably done in accordance with standard time and standard methods, especially for ultra-long charging of more than 12 hours. Usually, the charging method described in the mobile phone manual is a standard charging method suitable for the mobile phone.

In addition, the lithium battery phone or charger will automatically stop charging after the battery is fully charged, there is no so-called “turbulent” charging that the nickel battery charger has for 10 hours. In other words, if your lithium battery is full, it will be white charger on the charger. And none of us can guarantee that the characteristics of the battery's charge and discharge protection circuit will never change and the quality will be foolproof, so your battery will be on the edge of danger for a long time. This is another reason why we oppose long charging.

In addition, on some mobile phones, after charging for more than a certain period of time, if you do not remove the charger, then the system will not stop charging, and will start the discharge-charge cycle. Perhaps the manufacturer of this approach has its own purpose, but it is clearly unfavorable for the life of the battery and the phone/charger. At the same time, long charging takes a long time and often needs to be carried out at night. In the case of China's power grid, the voltage at night is high in many places and fluctuates greatly. As mentioned earlier, lithium batteries are very delicate, and they are much less resistant to fluctuations in charge and discharge than nickel, which in turn poses additional risks. In addition, another aspect that cannot be ignored is that lithium batteries are also not suitable for over-discharge, and over-discharge is also disadvantageous for lithium batteries.

Rechargeable lithium ion battery

The rechargeable lithium-ion battery is currently the most widely used battery in mobile phones, but it is more "squeaky" and cannot be overcharged or over-discharged during use (which can damage the battery or cause it to be scrapped). Therefore, there are protective components or protection circuits on the battery to prevent expensive battery damage. Lithium-ion battery charging requirements are very high, to ensure that the termination voltage accuracy is within 1%. At present, various semiconductor device manufacturers have developed a variety of lithium-ion battery charging ICs to ensure safe, reliable and fast charging.

Mobile phones are now very common, some of them are nickel-metal hydride batteries, but smart phones are lithium-ion batteries. Proper use of lithium-ion batteries is important to extend battery life. Lithium-ion batteries are currently the most widely used lithium batteries. They can be made into flat rectangular, cylindrical, rectangular and button type according to the requirements of different electronic products, and have a battery pack composed of several batteries connected in series. Lithium-ion batteries are rated at 3.6V (some products are 3.7V). The termination charge voltage at full charge is related to the battery anode material: the anode material is 4.2V for graphite; the anode material is 4.1V for coke. The internal resistance of different anode materials is also different. The internal resistance of the coke anode is slightly larger, and the discharge curve is slightly different. It is generally called 4.1V lithium ion battery and 4.2V lithium ion battery. Most of the current use is 4.2V, and the termination discharge voltage of the lithium ion battery is 2.5V to 2.75V (the battery factory gives the operating voltage range or gives the termination discharge voltage, and the parameters are slightly different). Continued discharge below the termination discharge voltage is called over discharge, and over discharge can damage the battery.

Lithium-ion batteries are not suitable for high-current discharges. When excessive current is discharged, the discharge time is reduced (the internal temperature is higher and the energy is lost). Therefore, the battery production plant gives the maximum discharge current, which should be less than the maximum discharge current in use. Lithium-ion batteries have certain temperature requirements. The factory gives the charging temperature range, discharge temperature range and storage temperature range. Lithium-ion batteries have high requirements for charging, and they require sophisticated charging circuits to ensure safe charging. The termination charge voltage accuracy tolerance is ±1% of the rated value (for example, a 4.2V lithium-ion battery with a tolerance of ±0.042V), and over-voltage charging can cause permanent damage to the lithium-ion battery. Lithium-ion battery charging current should be based on the recommendations of the battery manufacturer and require a limited current circuit to avoid overcurrent (overheating). The commonly used charging rate is 0.25C to 1C (C is the capacity of the battery, such as C=800mAh, and the charging rate of 1C is 800mA). It is often necessary to detect the battery temperature during high current charging to prevent overheating from damaging the battery or exploding.

Lithium-ion battery charging is divided into two phases: first constant current charging, to constant voltage charging when it is close to the termination voltage. This is a 800mAh capacity battery with a termination charging voltage of 4.2V. The battery is charged at a constant current of 800 mA (charging rate 1C). At the beginning, the battery voltage is boosted with a large slope. When the battery voltage is close to 4.2V, it is changed to 4.2V constant voltage charging, the current gradually decreases, and the voltage does not change much. When the charging current drops to 1/10C (about 80mA), it is considered to be nearly full, and charging can be terminated (some chargers start the timer after 1/10C, and end charging after a certain period of time). If the lithium ion battery is overcharged, over discharged or overcurrent during charging or discharging, it may cause damage to the battery or reduce the service life.

Lithium-ion battery application precautions In addition to the above non-rechargeable lithium battery, the following points should be noted in charging:

1. Lithium-ion batteries have different types of 4.1V and 4.2V termination charging. Therefore, when charging, the 4.1V battery cannot be charged with the 4.2V charger, otherwise there will be danger of overcharging (4.1V and 4.2V). The charger IC for the charger is different!).

2. When charging the battery, its ambient temperature should not exceed the temperature range listed in the product characteristics table.

3. Can not reverse charge.

4. It is not possible to charge a lithium-ion battery with a charger filled with nickel-cadmium batteries (three-cell nickel-cadmium batteries) (although the rated voltage is 3.6V), but the charging method is different, which may cause overcharging.

Pay attention to the following points in terms of discharge:

1. The discharge current of the lithium ion battery should not exceed the maximum discharge current given in the product characteristics table. When the discharge current is large, a higher temperature (loss energy) is generated, and the discharge time is reduced. If there is no protection element in the battery, overheating may damage the battery.

2. The discharge curves are different at different temperatures, and the discharge voltage and discharge time are also different. The worst case is when discharging at -20 °C.

In terms of storage:

1. If the battery is stored for a long time, it should be kept at 50% discharge state.

2. The battery should be stored in a low temperature, dry environment.

3. Keep away from heat and keep out of direct sunlight.

The analogy of the working principle of the image:

Now the principle and charge and discharge mechanism of lithium-ion batteries are compared with the foam phenomenon that is common in life. Lithium-ion batteries are like a pile of soap foam, and the energy stored in the bubble is electricity. When charging, the bubble will increase as the charging time is lengthened. When it exceeds its limit value, the bubble will rupture, which will damage the lithium crystal form and cause permanent damage.

When over-discharged, the bubble will collapse and disappear, so that the bubble will not be charged during the next charge, causing the lithium battery to fail. How to control the bubble not to burst and the bubble does not collapse too much? It must be strictly controlled by a protection circuit. Of course, high-quality batteries and precise control circuitry can greatly extend battery life.