The correct charging method and detailed explanation of the charging process for the lithium battery of electric vehicles

lithium battery charging

Nowadays, lithium batteries are used in mobile phones, notebook computers and even automobiles. This kind of battery is used as a secondary battery, which can be charged many times and is easy to use. However, there are many opinions and even misunderstandings about the lithium battery charging method. So, which are the correct lithium battery charging methods? Get a new electronic device, for the new lithium battery, how to charge it correctly? This article sorts out the commonly used charging methods for lithium batteries such as mobile phones, electric vehicles, and automobiles. Of course, you must know why. The correct use of lithium batteries is inseparable from the understanding of the charging and discharging process of lithium batteries.

Electric vehicle lithium battery charging method

21700 3S2P 8Ah Battery
21700 3S2P 8Ah Battery

1st, when charging for the first time, it is the same as the usual charging, no special treatment is required, and it can be charged for eight to twelve hours.

2nd, you must use the special charger provided by the lithium battery manufacturer for charging. When charging, first connect the output port of the charger to the battery, and then connect the charger to the power supply.

3rd, since the lithium battery has no memory effect, it can be charged whenever it is used, which is good for the life of the battery. It is recommended to charge it for eight to twelve hours each time, and the longest time should not exceed one day.

4th, in the case of long-term non-use, it is necessary to charge the lithium battery for two hours every two months, otherwise the performance of the battery will decrease. In addition, try not to charge the battery after the battery is completely discharged.

Mobile phone lithium battery charging method

Mobile phone charging
Mobile phone charging

Lithium batteries generally have a “shelf life” of 3 years, and they will decay quickly no matter whether they are used or not. Also pay attention to the full charge cycle of lithium batteries, which decays quickly after about 400-500 cycles. It depends on whether you use it for 3 years first or charge it to the number of times first.

Lithium batteries are not only afraid of low power, but also afraid of heat, especially when charging, if the phone case has poor heat dissipation, you must take it off. The long-term storage method of lithium batteries is to charge to 40% and put them in the refrigerator, but remember not to freeze them.

Don’t always wait until the battery runs out to recharge, this will speed up its loss. When the lithium battery is in low power, the loss is relatively large. Long-term 40%-60% power can make it last longer, but for frequently used equipment, this is impossible, but you can always keep it at 100%, that is, often Charging, do not pull out after charging. It will not be overcharged, and it uses the power of the power supply at this time, and the battery will not waste chargecycle, so it is beneficial to prolong life.

Lithium battery can be used when charging, the battery is not charging while discharging, there are two circuits in the mobile phone, one for charging the battery, and one for powering the machine directly through AC.

Connecting to the power supply after charging will not cause any harm to the lithium battery, because it is directly powered by the power supply, which reduces the number of charging and is beneficial to prolong the battery life.

(to be discussed) Always charging when the battery is above 90% but below 100% is not good for lithium batteries, ie always “topping off”. Thinkpad notebooks have a mechanism that allows the battery to not charge when it is above 90%.

There’s absolutely no harm in charging it overnight because you’re not using it and it doesn’t generate heat. Personally, I think overcharging is never a good thing. It is best not to charge at night. In some areas, the voltage is unstable at night, which is harmful to the machine!

Correct charging method of NCM lithium battery

NCM battery charging
NCM battery charging

Use the matching charger to fully charge the NCM lithium battery and then charge it for an hour.

Discharge until there are about 20℅ left, and then recharge. Excessive discharge will damage the NCM lithium battery.

When charging NCM lithium, try to fully charge it at one time.

The correct way to charge a new lithium battery

When using a lithium battery, it should be noted that the battery will enter a dormant state after being placed for a period of time. At this time, the capacity is lower than the normal value, and the use time is also shortened.

Lithium batteries are easy to activate, as long as they go through 3-5 normal charge and discharge cycles, the battery can be activated and the normal capacity can be restored.

Due to the characteristics of the lithium battery itself, it has almost no memory effect. Therefore, the new lithium battery in the user’s mobile phone does not need special methods and equipment during the activation process.

Two common misunderstandings of lithium battery charging methods

As for the charging method of the new battery, the most popular folklore is “the first three times should be charged for more than 12 hours to activate the battery”, in fact, this statement is wrong.

Reason 1: This statement is continued from nickel batteries, but the charging and discharging characteristics of lithium batteries and nickel batteries are very different. For lithium batteries, over-discharging and over-charging will cause serious damage to the battery, so the best It is best to charge according to the standard time and standard method, and remember not to charge for more than 12 hours.

Reason 2: The lithium battery will automatically stop charging after it is fully charged, but if it has been placed on the charger, a discharge-charge cycle may occur, and the characteristics of the battery’s charge-discharge protection circuit may change, and the battery is on the verge of danger.

“Recharge as you use it” or “recharge when you need to automatically shut down when there is no power left”? Many people will choose the latter when buying a new machine, but in fact it is not necessary.

Reason 1: The life of a lithium battery is generally 300~500 charging cycles. Assuming that the power provided by a complete discharge is 1Q, regardless of the fact that the power will decrease after each charging cycle, the lithium battery can provide a total of 300Q~500Q of power . If you charge 1/2 every time, you can charge 600-1000 times; if you charge 1/3 every time, you can charge 900-1500 times; if you charge randomly, the number of times is variable. In short, a total of 300Q-500Q of electricity that can be supplemented is constant. Therefore, the life of a lithium battery is related to the total charging capacity of the battery, but has nothing to do with the number of charges. Deep charging or shallow charging does not have much impact on the life of the lithium battery.

Reason 2: In fact, shallow discharge and shallow charging are more beneficial to lithium batteries. Only when the power module of the product is calibrated for lithium batteries, is it necessary to deep discharge and deep charge. Therefore, in the daily use process, you don’t have to stick to using photoelectric recharging, you can recharge it as you use it, and put convenience first.

Detailed explanation of lithium battery charging process

The most suitable charging process for lithium-ion batteries can be divided into four stages: trickle charging, constant current charging, constant voltage charging, and charging termination. Refer to Figure 1.

Detailed explanation of lithium battery charging process
Detailed explanation of lithium battery charging process

Phase 1: Trickle Charge – Trickle charge is used to precharge fully discharged cells first (recovery charge). When the battery voltage is lower than about 3V, first use the maximum constant current of 0.1C to charge the battery.

Phase 2: Constant current charging – when the battery voltage rises above the trickle charging threshold, the charging current is increased for constant current charging. The constant current charging current is between 0.2C and 1.0C. The current during constant current charging is not required to be very accurate, and quasi-constant current is also acceptable. In linear charger designs, the current is often ramped up as the battery voltage rises to minimize thermal issues on the pass transistor.

Constant current charging greater than 1C will not shorten the entire charging cycle time, so this approach is not advisable. When charging at a higher current, the battery voltage rises more rapidly due to the overvoltage of the electrode reaction and the voltage rise across the battery’s internal impedance. The constant current charging phase will be shortened, but the overall charging cycle time will not be shortened because the time of the following constant voltage charging phase will be increased accordingly.

Phase 3: Constant voltage charging – when the battery voltage rises to 4.2V, the constant current charging ends and the constant voltage charging phase begins. For best performance, the regulation tolerance should be better than +1%.

Phase 4: Termination of charge – Unlike nickel batteries, continuous trickle charging of Li-ion batteries is not recommended. Continuous trickle charging will cause plate plating effect on lithium metal. This destabilizes the battery and has the potential to cause a sudden automatic rapid disassembly.

There are two typical charging termination methods: using the minimum charging current to judge or using a timer (or a combination of the two). The minimum current method monitors the charging current during the constant voltage charging phase and terminates charging when the charging current decreases to the range of 0.02C to 0.07C. The second method counts from the beginning of the constant voltage charging phase, and terminates the charging process after two hours of continuous charging.

The above four-stage charging method takes approximately 2.5 to 3 hours to fully charge a fully discharged battery. Advanced chargers also incorporate more safety measures. For example, if the battery temperature exceeds a specified window (typically 0°C to 45°C), then charging is suspended.

After reading the above introduction, you know the correct lithium battery charging method. It can also be seen from the lithium battery charging curve that the lithium battery charging process is divided into 4 stages. According to the characteristics of each stage, we can not only do Proper use of lithium batteries, better protection of lithium batteries, avoid improper operation that may cause damage to lithium batteries.

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