CN101299542A - Control method for quickly charging battery - Google Patents

Abstract

The invention discloses a cell fast charge control method based on the theory of 'direct current charging measurement', including changing the charging current, to obtain the internal resistance size of cell through detecting the changing condition at the two end of the secondary battery or the battery; then realtime outputting the controlling quantity of the charging current according to the range of the internal resistance of the cell and the measured adjusting strategy; meanwhile determining end of the fast charge process according to that whether the surface temperature exceeds the set value or the battery charging voltage is present with minus delta U, to reach the object of safe, fast and high efficiency charging. The invention has simple realization and marked effect; the inventive charger can effectively prolong the service life of the secondary cell and advance the availability of the secondary cell.

Description

Battery fast charging control method

technical field

The invention relates to a fast charging control method for a secondary battery that uses a "direct current charging measurement method" to detect and judge the change state of the internal resistance of a secondary battery to realize safe and fast charging. Specifically, it is a battery fast charging control method based on the principle of "DC charging measurement method".

Background technique

With the popularization of portable electronic products and electric vehicles, the role of secondary batteries that provide them with electrical energy has changed from a "supporting role" in the past to a "key" component. At the same time, due to the continuous use of these products and tools, the application of safe and fast charging technology for secondary batteries is becoming more and more important. However, the fast charging modes currently used have certain limitations. Especially when the internal resistance of some secondary batteries that have been used for a long time is relatively large, once a large current is used for fast charging, a large overshoot current will be generated, resulting in charging failure and unusable, resulting in unnecessary waste. Therefore, it is particularly important to design a simple and feasible fast charging device that adjusts charging parameters according to the internal state of the battery to meet the charging requirements of batteries in various states. There is no such simple and effective control method on the market at present.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a battery fast charging control method based on the principle of "DC charging measurement method". The method adopts the "DC charging measurement method" to detect and judge the change state of the internal resistance of the secondary battery, and reasonably adjusts the charging current according to the size of the internal resistance of the battery, so as to realize safe and fast charging. The invention quickly and safely controls the charging of the secondary battery in various states including large internal resistance, and can effectively prolong the service life of the secondary battery.

The purpose of the present invention is achieved through the following technical solutions:

A method for controlling fast charging of a battery, characterized in that: while changing the charging current, the method obtains the size of the internal resistance of the battery at the moment by detecting the change in the voltage of the secondary battery, and realizes the optimal fast charging according to the internal state of the battery. control; it includes the following steps:

1) During the charging process of a battery or battery pack with a certain current I, a charging current ΔI is superimposed instantaneously, that is, the charging current becomes I+ΔI, and this superimposed current generates a voltage increment ΔU= on the internal resistance of the battery U2-U1, measure the voltage U1 and U2 at both ends of the battery or battery pack before and after the charging current is superimposed;

2) Calculate the voltage increment ΔU=U2-U1 according to the measured voltages U1 and U2, and calculate the value of the internal resistance R _i of the battery at this moment from ΔI and ΔU: R _i =(U2-U1)/(I+ΔI- I) = ΔU/ΔI.

3) According to the measured and calculated current value of the internal resistance of the battery, determine whether to increase or maintain the value of the charging current, and determine the adjustment strategy of the nth charging current I _n according to the following fuzzy control rules:

If the internal resistance R _n-1 of the n-1th measurement is large, that is, the measured value exceeds 30% of the standard value, then I _n =I _n-1 ;

If the internal resistance R _n-1 of the n-1th measurement is relatively large, that is, the measured value exceeds the standard value by 1% to 30%, then I _n =I _n-1 +I _d , where I _d is the current unit increment;

If the internal resistance R _n-1 of the n-1th measurement is not large, that is, the measured value is within the allowable fluctuation range of the standard value, then I _n =I _n-1 +kI _d , (k=2, 3, 4) ;

If the internal resistances R _n-3 , R _n-2 and R _n-1 measured three times in a row are not large, then I _n =I _max , where I _max is the maximum charging current;

4) The optimal control of fast charging is achieved through the above regulation strategy.

The present invention is a battery fast charging control method based on the principle of "DC charging measurement method". It uses a single-chip computer as a controller to measure, calculate and analyze the charging state of the secondary battery, and control and adjust the charging current of the battery; If the surface temperature of the battery or battery pack exceeds the set value or the charging voltage of the battery or battery pack continuously appears -ΔU, set _In = I _small , end fast charging, and change to trickle charging, where I _small is 0.05C.

The present invention is based on the principle of "DC charging measurement method". While changing the charging current, the internal resistance of the battery at the moment is obtained by detecting the change of the secondary battery voltage, and the optimal control of fast charging is realized according to the internal state of the battery; it The advantages are: 1. The variation of the internal resistance of the secondary battery can be quickly calculated to determine the appropriate charging current. The method is simple and safe; 2. The present invention can effectively charge the secondary battery with a large internal resistance. The service life of the secondary battery can be extended.

The invention is safe, economical, practical and easy to realize.

Description of drawings

Fig. 1 is a block diagram of the circuit structure of the battery fast charging control system in the present invention;

Figure 2 shows the transient voltage and current waveforms during DC charging.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Accompanying drawing 1 shows the block diagram of the circuit structure of the battery fast charging control system based on the principle of "DC charging measurement method". The control system includes: a controllable charging current circuit 1 , a current detection circuit 2 , a voltage detection circuit 3 , a temperature detection circuit 4 , a single chip computer 5 and a battery or a battery pack 6 . The controllable charging current circuit 1 provides charging current to the charged battery or battery pack 6 under the control of the single-chip computer 5; the current detection circuit 2 is used to measure and provide the adjusted charging current value to the single-chip computer 5; the voltage detection circuit 3 is used to It detects the instantaneous voltage at both ends of the battery or battery pack 6 and sends it to the single-chip computer 5; the temperature detection circuit 4 is used to measure the surface temperature of the battery or battery pack 6 and sends it to the single-chip computer 5; The change of battery terminal voltage caused by the moment of current change, calculate the increment of charging current correction and adjust the value of battery charging current according to the feedback signal of the current detection circuit; at the same time, when the temperature of the battery or battery pack 6 exceeds the upper limit or the battery Or if the charging voltage of the battery pack is -ΔU for a certain period of time, the fast charging is terminated, and the charging current I _n =I _small is changed to trickle charging.

Accompanying drawing 2 is the transient voltage and current variation waveform during DC charging. At the beginning, the single-chip computer controls the controllable charging current circuit to charge the secondary battery with a certain current I, and then superimposes a charging current increment ΔI at regular intervals, and this superimposed current must exceed the internal resistance of the battery. Will produce a voltage increment ΔU=U2-U1, as shown in Figure 2.

From the formula: R≈(U2-U1)/(I+ΔI-I)=ΔU/ΔI, the current DC internal resistance Ri of the battery can be approximately calculated. Then, according to the calculated battery internal resistance, determine the adjustment strategy for the next charging current I _n :

If the internal resistance R _n-1 of the n-1th measurement is large, that is, the measured value exceeds 30% of the standard value, then I _n =I _n-1 ;

If the internal resistance R _n-1 of the n-1th measurement is relatively large, that is, the measured value exceeds 1% of the standard value and does not exceed 30% of the standard value, then I _n = I _n-1 + I _d , where I _d is the current unit increment;

If the internal resistance R _n-1 of the n-1th measurement is not large, that is, the measured value is within the allowable fluctuation range of the standard value, then I _n =I _n-1 +kI _d , (k=2, 3, 4) ;

If the internal resistances R _n-3 , R _n-2 and R _n-1 measured three times in a row are all small, then I _n =I _max , where I _max is the maximum charging current.

The present invention uses a single-chip computer as the core of the control system to measure, calculate and analyze the charging state of the secondary battery, and control and adjust the charging current of the battery; If the voltage continuously appears -ΔU, set In=I _small , end fast charging, and change to trickle charging, where I _small is 0.05C.

It is proved by experiments that the present invention can not only realize fast charging control of batteries with relatively large internal resistance, but also timely detect deteriorated (excessive internal resistance) storage batteries, and eliminate potential hidden dangers of storage batteries (or storage battery packs). The invention has the characteristics of simple test, convenient calculation and easy circuit realization, can effectively improve the availability rate of the battery, and is suitable for product application and popularization.

Claims (2)

1, a kind of control method for quickly charging battery, it is characterized in that: this method is when changing charging current, obtain the size of the internal resistance of cell this moment by the variation that detects secondary cell voltage, and realize the Optimal Control of quick charge according to the internal state of battery; It may further comprise the steps:

1) battery or battery pack with a certain electric current I charging process in, the moment charging current Δ I that superposes, be that charging current becomes I+ Δ I, the electric current of this stack produces a voltage increment Δ U=U2-U1 in the internal resistance of battery, measure the voltage U 1 and the U2 at charging current stack front and back battery or battery pack two ends;

2) calculate voltage increment Δ U=U2-U1 according to measured voltage U 1 and U2, obtain internal resistance of cell R this moment by Δ I and Δ U _iValue: R _i=(U2-U1)/(I+ Δ I-I)=Δ U/ Δ I.

3) according to the internal resistance of cell currency of measuring and calculating, determining to increase still is the value that keeps charging current, and determines charging current I the n time according to following fuzzy control rule _nThe adjusting strategy:

If the internal resistance R that measures for the n-1 time _N-1For greatly, I then _n=I _N-1

If the internal resistance R that measures for the n-1 time _N-1For bigger, I then _n=I _N-1+ I _d, I wherein _dBe the current unit increment;

If the internal resistance R that measures for the n-1 time _N-1For not quite, I then _n=I _N-1+ kI _d, (k=2,3,4);

If continuous three measured internal resistance R _N-3, R _N-2And R _N-1All little, I then _n=I _Max, I wherein _MaxBe maximum charging current;

4) by realize the Optimal Control of secondary cell quick charge with the adjusted strategy.

2, control method for quickly charging battery according to claim 1 is characterized in that: adopt monolithic computer as controller, measure, calculate and analyze the charged state of secondary cell, the charging current of control and regulating cell; If battery or battery surface temperature surpass the voltage of set point or battery or batteries charging and occur continuously-Δ U, then make I _n=I _Small, finish quick charge, change trickle charge into, wherein I _SmallBe 0.05C.

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