Battery overdischarge degree detection method
Technical Field
The invention relates to the technical field of battery detection, in particular to a battery overdischarge degree detection method.
Background
The battery has high energy density, long cycle life and portability, and is widely applied to various fields, such as electronic equipment, energy storage power stations, transportation vehicles and the like.
The batteries are often used in groups in actual use, which has a high requirement on the consistency of the batteries, when the consistency between the battery packs is poor, or after a related battery management system fails, a part of battery cells are over-discharged, the overall performance of the battery pack is often determined by the worst battery cell, therefore, it is very important to detect the degree of over-discharge of the batteries, which is important for determining whether the batteries can be used again after over-discharge, however, the detection of the degree of over-discharge of the batteries is only simply determined by setting a corresponding threshold, and the degree of over-discharge of the batteries cannot be accurately detected.
Disclosure of Invention
The present invention is directed to a method for detecting overdischarge level of a battery, which overcomes the above-mentioned drawbacks of the prior art.
The purpose of the invention can be realized by the following technical scheme:
a battery overdischarge degree detection method comprises the following steps:
1) discharging the standard battery to cut-off voltage to become a discharge state standard battery;
2) overdischarging the standard battery in the discharge state;
3) acquiring the state of charge (SOC) and the voltage (V) of the discharge state standard battery in the overdischarge process in real time, and acquiring a relation V (f) (SOC) between the state of charge (SOC) and the voltage (V) of the discharge state standard battery;
4) overdischarge is carried out on the battery to be tested, and terminal voltage V when the overdischarge of the battery to be tested is terminated is obtained0;
5) Charging the overdischarge battery to be tested according to a standard charging mode, and recording whether the overdischarge battery can be fully charged or not;
6) combining the terminal voltage V when the over-discharge of the battery to be tested is terminated according to the relation V (f) (SOC) between the state of charge SOC and the voltage V of the standard battery in the discharge state0And whether the battery to be tested can be fully charged or not is judged to obtain the overdischarge degree of the battery to be tested.
In the step 1), the cut-off voltage is specifically the cut-off voltage for battery discharge specified by a battery manufacturer.
In the step 2), the discharge-state standard cell is overdischarged after the discharge-state standard cell is connected in series with a plurality of full-state cells.
In the step 2) and the step 4), the over-discharge mode is constant current discharge.
And in the step 3), the SOC of the battery is obtained by adopting a direct obtaining method, an ampere-hour integration method or a capacity ratio method.
In the step 3), the voltage V is specifically a battery terminal voltage corresponding to the state of charge SOC during the overdischarge process.
In the step 3), in a relation curve between the state of charge SOC and the voltage V of the discharge state standard battery, the ordinate is the voltage V, the abscissa is the state of charge SOC, and the range is 0-100%.
In the step 3), in the relation curve between the state of charge SOC and the voltage V of the discharge state standard battery, the voltage Vminimum is VminState of charge value of time SOCmThe state of charge value is between 0 and SOCmWithin the range, the voltage V is monotonically decreased and the state of charge value is at SOCmWhen the charge state value is-100%, the corresponding voltage V is less than 0.
In the step 6), the obtaining of the overdischarge degree of the battery to be tested specifically includes:
terminal voltage V when overdischarge of a battery under test is terminated0When the voltage is larger than zero, the relation V (f) (SOC) between the SOC and the voltage V of the discharge state standard battery and the terminal voltage V when the overdischarge of the battery to be tested is terminated are determined0And determining the over-discharge charge state of the battery to be tested.
In the step 6), the obtaining of the overdischarge degree of the battery to be tested specifically includes:
terminal voltage V when overdischarge of a battery under test is terminated0When the voltage is less than zero, according to the relation V (f) (SOC) between the state of charge SOC and the voltage V of the discharge state standard battery and the terminal voltage V when the over-discharge of the battery to be tested is terminated0Determining the state of charge SOC of two possible overdischarges of a battery1And SOC2And SOC1|<|SOC2Charging the battery to be tested, and if the battery to be tested can be fully charged, the overdischarge degree of the battery to be tested is a state of charge SOC with a small absolute value1If the battery to be tested can not be fully charged, the overdischarge degree of the battery to be tested is the state of charge SOC with a larger absolute value2。
Compared with the prior art, the invention has the following advantages:
according to the characteristic of a relation V (f) (SOC) curve between a state of charge (SOC) and a voltage V of a discharge state standard battery, the overdischarge degree of the battery can be obtained only by obtaining a terminal voltage of the battery at the end of overdischarge in actual detection, extra detection equipment is not required to be added, and the overdischarge degree of the battery can be accurately diagnosed in actual application.
Drawings
FIG. 1 is a general flow diagram of the present invention.
Fig. 2 is a graph of state of charge versus voltage for a battery overdischarge.
Detailed Description
As shown in fig. 1, the present invention provides a method for detecting overdischarge degree of a battery, which comprises the following steps:
1) discharging the standard battery to a cut-off voltage, namely the cut-off voltage of battery discharge specified by a battery manufacturer;
2) connecting other full-state batteries and discharge-state standard batteries in series, and performing constant-current discharge on the discharge-state standard batteries;
3) acquiring a state of charge (SOC) of a discharge state standard battery in an overdischarge process and a battery terminal voltage corresponding to the SOC in the overdischarge process, wherein the SOC in the embodiment adopts a mode including but not limited to direct acquisition, an ampere-hour integration method and a capacity ratio method;
4) obtaining the relation between the charge state and the voltage of the discharge state standard battery in the overdischarge process;
5) carrying out overdischarge test on a battery to be tested, and acquiring a terminal voltage when overdischarge of the battery is terminated;
6) charging the overdischarge battery according to a standard charging mode;
7) determining the overdischarge degree of the battery together according to the terminal voltage of the battery to be tested at the over-discharge end and the result of whether the battery can be fully charged, specifically:
and when the terminal voltage of the battery to be detected at the over-discharge end is larger than zero, determining the over-discharge charge state SOC of the battery to be detected by using the over-discharge voltage of the battery to be detected according to the relation between the charge state and the voltage of the battery.
When the terminal voltage of the battery to be detected at the end of overdischarge is less than zero, determining the overdischarge charge states SOC of two possible batteries by using the overdischarge voltage of the battery to be detected according to the relationship between the charge states and the voltage of the battery, then charging the battery to be detected, and if the battery to be detected can be fully charged, determining the overdischarge degree of the battery to be detected to be the charge state SOC with a smaller absolute value; and if the battery to be tested cannot be fully charged, the overdischarge degree of the battery to be tested is the state of charge SOC with a larger absolute value.
The specific principle is as follows:
if the battery to be tested can be fully charged in a constant-current and constant-voltage mode according to the standard specified by a manufacturer, the overdischarge degree of the battery to be tested is a charge state with a small absolute value.
Examples
The experimental object in the embodiment of the invention is a soft package lithium ion battery, a fully discharged battery and the other four fully charged batteries are connected in series, and an overdischarge test is carried out on a charge and discharge test bench at room temperature of 25 ℃. The battery in a discharge state is completely overdischarged to-100% SOC, during which the terminal voltage and the discharge capacity of the battery are obtained in real time, the SOC of the overdischarge of the battery is obtained according to the ratio of the discharged capacity to the standard capacity of the battery, so as to obtain the relation between the SOC and the terminal voltage of the battery when the battery is overdischarged, as shown in FIG. 2, in the embodiment, the battery to be detected is overdischarged to-1.93V, then the overdischarged battery is charged according to the standard charging mode, the battery cannot be fully charged, and the degree of the overdischarge of the battery is judged to be-14.8% SOC according to the relation between the SOC of the overdischarge of the battery and the terminal voltage of the battery.
The above description is only exemplary of the present invention, and not intended to limit the present invention, and all the modifications and variations are included within the spirit and scope of the present invention.