Basic concept and charging knowledge of lithium battery

The lithium battery charging ratio of C: used to say battery when charging and discharging current size ratio, namely the ratio. As the 1200 mAh battery, 0.2 C said 240 ma (1200 mAh ratio 0.2), 1 C said 1200 ma (1200 mAh 1 ratio).Charge and discharge efficiency is also associated with C (ratio), under the condition of 0.2 C, polymer lithium battery charge and discharge efficiency should be at 99.8%.Charge and discharge efficiency = discharge capacity/charging capacity by 100%

Lithium electricity rated capacity of the pool: refers to the battery after a full charge, light condition to devolve power to cut off voltage, can release of electrical energy, general with mAh or Ah Ah (1 = 1000 mAh) symbol. But if the battery connection when using load and use for a long time after the battery release of electricity will decline. Capacity is due to the charge and discharge under the certain condition of C - rate, so the capacity of the battery is directly related to the C - rate. Normally nominal capacity of battery is 0.2 C electric capacity under the condition of test. C - the greater the ratio, the smaller the battery discharge rate. Charging capacity (Ah or mAh) = (charging time, charging current discharge capacity (Ah or mAh) = x discharge current discharge time. In general, basic can achieve 0.2 C discharge current discharge rate 95% ~ 100%, and 1 C discharge current can only can reach the discharge rate is about 90%.

The usefulness of lithium battery charging ratio of C:

We are reading the battery specification or technical requirements and the related articles about charge discharge will be found that there often mentioned "charge" in 0.5 C, "maximum discharge current should not exceed 2 C, general control under 1 C." Because, each battery charge and discharge requirements are different, and for the same type of battery, often is the charge and discharge current value is a C, because nature with its capacity (that is, the milliampere hours), so, define a C, is a standard unit of meaning.

By the lithium battery charging ratio C, we can know some basic common sense.

1 How long the rechargeable lithium-ion batteries?

Normally recommended standard lithium-ion batteries charging time is 15 hours, this is how to calculate? Said, in front of the charging current associated with C, generally set to 0.1 C of charging current, so, in theory should be 10 hours, however, generally considering the problem of charging efficiency, manufacturers suggest check the capacity of 1.5 times, so the standard time is 15 hours.

Of course, few charge for so long now. Performance improvement due to the battery itself, can withstand the charging current increases, the natural time is shortened. Such as lithium-ion batteries, quick charge mode generally set to 0.3C to 1C, but generally the lower the recommended more conducive to battery life and charging efficiency, general under 0.5 C as well.

To add stressed the point is: the lithium battery charging current and charging time and is not a simple linear relationship between.

Charging at a rate of about 0.1 C, for example, only need 15 hours, does not mean that is filled to capacity of 1.5 times, it is mainly the relationship between the charging efficiency, and my understanding is that constant current charge in the different time into the capacity is not constant.

2 the concept of lithium-ion battery discharge depth

The so-called depth of discharge, is refers to the discharge and store energy by the ratio of (standard capacity).The smaller the number, means that discharge more shallow. For example, the discharge depth is 20%, that is to say in the remaining 80% of capacity.

Two concepts associated with lithium battery discharge depth:

1 and the service life of the relationship, the deeper the depth of discharge, the easier it is to shorten the service life. Factors related to the life is more, it besides associated with the depth of discharge, also related to the discharge rate. Simple said, is "slow", "whole".

2 in addition, the depth of discharge go deeper, the voltage and current can't guarantee anything. On the other hand, most of the time, power meter, power consumption as the battery work termination conditions, also is the platform in order to guarantee a certain voltage and current, the other is from life.

3 Way to lithium batteries

There are two kinds of lithium battery charging ways, simpler is pure constant current. The CC tends to cooperate with the charging time control. More advanced and more typical is the CC/CV, namely the constant current + constant pressure. That is to say, start with a larger charging rate, this phase is called quick charge, charge to a voltage threshold, turn into trickling water filling pattern, make the voltage rise to the highest voltage bit by bit, this time, the capacity is close to the standard capacity, and at the end of the quick charge mode, generally translates to about 80%.

The threshold voltage is called the over voltage threshold, lithium-ion battery now most of the high voltage to 4.35 V, in the face of this situation, a recommended standard threshold is 4.2 V. But, remember, it's just a statistics, most of the time, we will choose a slightly lower, but also cannot too low, too low charging efficiency is not high.

Have some more advanced charging scheme and a prefilled stage.

What is this concept? Said, in front of the discharge is too deep, voltage drop so much, and will damage the lithium battery. If we are in the quick charge before such excessive discharge of battery, there is a trickling water filling pattern of moderate process, can give a part to repair damaged cells.

The page contains the contents of the machine translation.