A kind of quick effective ratio is compared with the method for battery self discharge rate sizeTechnical field
The present invention relates to the method for a kind of quick effective ratio compared with battery self discharge rate size.
Background technology
Along with country is to the progressively enhancing of the pay attention to day by day of environmental protection and people's environmental consciousness, lithium ion battery not only in traditional digital product, and is applied to electric tool, electric bicycle, even electric automobile and large-scale energy storage device more and more widely.When lithium ion battery applications is in mobile phone or this kind of digital product of camera, owing to being the connection in series-parallel between single to be only used alone without the need to battery, therefore require lower to the overall performance of battery, only need capacity and cycle performance qualified.But when being applied to the higher field of the operating voltage such as electric bicycle, electric automobile, need many batteries to connect to reach required voltage.When serial battery uses, even if now single battery capacity circulating performance is qualified but do not ensure that the performance of integral battery door group meets the requirements, also need battery with two side terminals coupling, i.e. said battery sorting pairing.When carrying out consistance coupling to battery, there are oneself parameter and matching process in each producer, as mated by the multiparameter such as curve degree coupling, comprehensive discharge capacity, constant current capacity, mean voltage, internal resistance, no matter which kind of matching process is all indispensable to selecting of self-discharge of battery.Why so important to the performance of electric battery be selecting of self-discharge of battery? illustrate: a 36V10Ah electric bicycle battery group is in series by 12 3.2V10Ah ferric phosphate lithium cells, suppose that the capacity of dispatching from the factory of every cell is 10Ah, there is the self-discharge rate of 11 batteries consistent in 12 cells, and remaining 1 exceeds 24mAh/ days than other battery self discharge rate, then after battery dispatches from the factory one month, the battery capacity of self discharge high rate will reduce 24*30=720mAh (0.72Ah) than other battery remaining power, now the overall discharge capacity of electric battery just only has 9.28Ah, capacitance loss rate reaches 7.2%.If single battery uses, the capacity now lost supplements by charging next time, does not affect later discharge performance, but when using in groups, during the high battery discharge of self-discharge rate, it is discharged at first, and now other battery capacity does not discharge yet, can not be full of by the battery that the restriction self-discharge rate of other battery charge capacity is high when charging, and self discharge difference is along with whole battery life cycle, so As time goes on, the capacity that the battery that self-discharge rate is high can fill is fewer and feweri compared with other battery, finally cause whole battery capacity defective, if therefore there is no balanced measure or carry out list only to supplement electricity, this loss will cannot make up.At present, select following several thinking to self-discharge of battery difference: one is the self-discharge current size measuring every battery, then mates by self-discharge current, this method is the absolute self-discharge rate measuring battery; Two is that the definition of foundation self discharge is to measure the self-discharge capacity in a period of time, concrete operation step is to setting voltage by constant-current charging of battery, turn constant-voltage charge subsequently until electric current is down to a certain value (being usually not less than 0.01C) stop charging afterwards, shelve, after arrival is shelved the time (usually reaching 28 days), battery is discharged, relatively shelve the capacitance loss of front and back battery, thus calculate the self-discharge capacity that it shelves period; Three is the relative self-discharge rates measuring battery, the same method two of its charging process of the method, difference is that it shelves the time shorter (usually within 14 days), after the time of shelving arrives, measure the open-circuit voltage of battery, be used as with the voltage drop of battery the foundation judging the relative self-discharge rate of battery.At present existing Application way one and the instrumentation made, but its price is high, battery determination period more than 12 hours, and once can only survey a battery, even if therefore this kind of mode test result is accurate, but its testing cost is too high, be not suitable for large-scale production, be only applicable to experiment at present and use; Method two is the standard method of test of general lithium ion battery to self-discharge rate, but it is oversize that its shortcoming is determination period, method three test period is relatively short and can test in batches, also be the selection method that current most producer is adopted aborning, therefore can be described as a kind of classic method selected and compare battery self discharge rate size, but experiment proves it, and to select effect unsatisfactory.
Therefore, a kind of quick effective ratio is needed compared with the method for battery self discharge rate size to solve the problem.
Summary of the invention
Goal of the invention: the defect that the present invention is directed in prior art the method comparing battery self discharge rate size, provides a kind of quick effective ratio compared with the method for battery self discharge rate size.
Technical scheme: for solving the problems of the technologies described above, quick effective ratio of the present invention adopts following technical scheme compared with the method for battery self discharge rate size:
Quick effective ratio, compared with a method for battery self discharge rate size, comprises the following steps:
1), under battery is normally full of electric state, continue to carry out modified constant-voltage charge to battery, until charging current is down to extremely low state or long-time stopping when a certain current value bob is charged, wherein, described extremely low state is that charging current is less than or equal to 0.001C, described long-time for being more than or equal to 1 hour;
2), by the battery through step 1) process shelve, the time of shelving is less than or equal to 7 days;
3), shelve end after, measure the open-circuit voltage of battery;
4) open-circuit voltage, by step 3) recorded and standard value compare, and open-circuit voltage is that self discharge is abnormal lower than the judgement of standard value, and open-circuit voltage is that self discharge is normal higher than the judgement of standard value.
Further, step 2) described in the time of shelving be 5 days.
Beneficial effect: the present invention is the improvement to classic method, by reducing the difference between charge cutoff electric current and normal battery self-discharge current, self-discharge of battery after charging stops is made to become the principal element causing cell voltage to decline, strengthen the matching relationship between voltage drop and self discharge, thus judge to compare self discharge difference between battery.Quick effective ratio of the present invention, compared with the relative classic method of the method for battery self discharge rate size, is significantly increased to the validity that battery self discharge rate is selected, and this method is applicable to scale and selects, and selects efficiency higher, more effectively.
Accompanying drawing explanation
Fig. 1 is battery simple equivalent circuit figure;
Fig. 2 be the battery shelved voltage that measures by traditional shelved voltage method and its shelve corresponding relation figure between rear capacitance loss rate;
Fig. 3 be the battery shelved voltage that adopts quick effective ratio of the present invention to measure compared with the method for battery self discharge rate size and its shelve corresponding relation figure between rear capacitance loss rate.
Embodiment
Below in conjunction with the drawings and specific embodiments, illustrate the present invention further, these embodiments should be understood only be not used in for illustration of the present invention and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within the application's claims limited range.
Refer to shown in Fig. 1, Fig. 2 and Fig. 3, quick effective ratio of the present invention, compared with the method for battery self discharge rate size, comprises the following steps:
1), under battery is normally full of electric state, continue to carry out modified constant-voltage charge to battery, until charging current is down to extremely low state or long-time stopping when a certain current value bob is charged, wherein, extremely low state is that charging current is less than or equal to 0.001C, for a long time for being more than or equal to 1 hour;
2), by the battery through step 1) process shelve, the time of shelving is less than or equal to 7 days; When scale is selected, under all batteries through step 1) process are placed on identical environment, shelve;
3), shelve end after, measure the open-circuit voltage of battery;
4) open-circuit voltage, by step 3) recorded and standard value compare, and open-circuit voltage is that self discharge is abnormal lower than the judgement of standard value, and open-circuit voltage is that self discharge is normal higher than the judgement of standard value.Wherein, standard value provides by experiment, and this standard value is applicable to the battery of the same manufacturer production of same recipe same process.
When studying the performance of battery, generally can by simple for battery equivalence one-tenth electric capacity as shown in Figure 1 and the circuit diagram of resistance.Self-discharge of battery can regard that the electric capacity pair conductive discharge in parallel with it cause as.When after stopping charging, the voltage of battery declines thereupon.But now the decline of cell voltage is caused by self discharge on the one hand, be then due to the current path caused that fades away when battery polarization after stopping charging on the other hand.For ferric phosphate lithium cell, its self-discharge current is generally less than 0.0001C, and the general not low 0.01C of charge cutoff electric current during tradition charging, when stopping charging, by polarizing, the current path caused will be far longer than the voltage drop caused by self discharge, and the latter is flooded completely by the former, unless therefore self discharge is abnormal especially, otherwise be difficult to find the voltage differences that causes because of self discharge, this point confirm by Fig. 2.The present invention is the improvement to classic method, by reducing the difference between charge cutoff electric current and normal battery self-discharge current, self-discharge of battery after charging stops is made to become the principal element causing cell voltage to decline, strengthen the matching relationship between voltage drop and self discharge, thus judge to compare self discharge difference between battery.In order to contrast classic method and actual effect of the present invention, choosing 20 3.2V10Ah batteries and testing, normal full electric charging process is: after 0.2C constant-current charge to 3.65V, turn constant-voltage charge, and when charging current reaches 0.01C, charging terminates.Shelved voltage in Fig. 2 records in a traditional way, and the shelved voltage in Fig. 3 then measures for the present invention, and namely continue to be less than 0.001C with constant-voltage charge to electric current, within 10 hours, to shelve subsequently in limited time after being normally full of electricity, the time of shelving is 5 days.After two kinds of methods measure the shelved voltage of battery, by charging normal mode, electricity is full of to experimental cell, then shelve for a long time (shelving 1 year), finally discharge, measure the battery remaining power shelved after a year, contrast with the capacity before shelving, calculate capacitance loss rate, again the corresponding battery shelved voltage that the capacitance loss rate of each experimental cell and two kinds of methods record is compared, obtain Fig. 2 and Fig. 3 respectively.As can be seen from the contrast of two figure, the voltage differences (9mV) that the relative classic method of shelved voltage difference (37mV) of 20 batteries that the present invention records records is obvious, and to done experimental cell, when shelved voltage is lower than 3420mV, its self-discharge capacity loss percentage is substantially all higher than 6%, and the shelved voltage that classic method measures, except its corresponding shelved voltage of battery that capacitance loss rate is maximum is lower, other battery and its capacitance loss rate are all without corresponding evident regularity.The relative classic method of the present invention, is significantly increased to the validity that battery self discharge rate is selected.
Quick effective ratio of the present invention, compared with the relative classic method of the method for battery self discharge rate size, is significantly increased to the validity that battery self discharge rate is selected, and this method is applicable to scale and selects, and selects efficiency higher, more effectively.