CN104730462A - Battery pack capacity online detecting method - Google Patents

Abstract

The present invention relates to electric vehicle technical field, in particular to a kind of battery capacity online test method. The detection method includes: t1 moment initial start-up vehicle, detects the open-circuit voltage OCV1 of battery this moment, and according to open-circuit voltage OCV1, obtains the state of charge SOC1 of battery pack this moment; The t2 moment is again started up vehicle, detects the open-circuit voltage OCV2 of battery this moment, and according to open-circuit voltage OCV2, obtains the state of charge SOC2 of battery pack this moment; The current capacity C of battery pack is calculated by following equation: Wherein, Q is the charge value that battery pack carries out charge and discharge in t1 and t2 time interval. Battery capacity online test method provided by the invention, it is ensured that in the case where vehicle operates normally, simply, effectively and reliably calculate the capacity of battery pack, it is ensured that the continual mileage of vehicle.

Description

A kind of battery capacity online test method

Technical field

The present invention relates to electric vehicle technical field, particularly a kind of battery capacity online test method.

Background technology

Along with the demand of global energy-conserving and environment-protective, the new energy vehicles such as pure electric automobile have become the main trend of automotive field, electrokinetic cell system provides power drive for entirety, plays vital effect, and the size of its capacity then directly has influence on the continual mileage of car load.

Under normal conditions, when battery system is initially installed on car load, the capacity of battery system is rated capacity, and at electric vehicle after the operation of certain hour, there is the factors such as aging and damage due to battery, a certain amount of decay will be there is in capacity, battery capacity is after overdamping, if do not monitor out damping capacity in time, so battery management system BMS (BatteryManagement System) still can carry out various algorithm (as SOC according to initial capacity, maximum permission charge-discharge electric power, continual mileage prediction etc.) words, the degree of accuracy of algorithm will be affected, and error increases along with the aggravation of capacity attenuation, carry out the usability affecting car load.

In prior art, the method usually adopted for capacity after monitoring cell decay comprises: discharge test method, DC internal resistance method, AC internal Resistance method or model prediction etc.

Wherein, after battery adopts the mode of constant-current discharge to discharge into cut-off voltage from fully charged state by discharge test method, thus calculate the constant-current discharge capacity of battery, its maximum shortcoming needs off-line test, namely need battery system to be uncarted come, then positive for battery negative output be connected on checkout equipment and detect, during detection, vehicle cannot be runed.

DC internal resistance rule is connected to after on checkout equipment by battery system, apply a big current and continue for some time, draw the DC internal resistance of power brick according to the pressure drop of cell voltage within this time period and the ratio of electric current, then draw the capacity after battery system decay according to the increase of DC internal resistance.

AC internal Resistance method and DC internal resistance method similar, by injecting the alternating current of a certain frequency to DC bus, test draws and compared with the initial AC internal Resistance of power brick, draws the AC internal Resistance of power brick attenuation degree, thus obtain the current actual capacity of power brick.

Above-mentioned internal resistance method, because the detection of internal resistance can be drawn by service data process in car load operational process, thus there is the advantage of on-line operation, but because the relation between the capacity of battery system and internal resistance is not too clear and definite, and because the internal resistance of power brick is all at the milliohm order of magnitude, absolute value is very little, is easily subject to the interference of the factors such as measuring error, thus makes the cell decay capacity measured larger with actual value phase ratio error.

The thinking of model prediction adopts a large amount of experimental datas by testing out, set up the mathematical model of battery capacity decay, using battery the parameter such as service time of process or total discharge and recharge as the input parameter of model, capacity after cell decay is as the output parameter of model, under the support of lot of experimental data, model more accurately can be drawn, under model accurately prerequisite, in the process that mesuring battary uses, the correlation parameter of actual motion is input in model, can show that model exports---the residual capacity after cell decay.But the method needs to carry out a large amount of battery life tests, take time longer, and measurement condition can not be identical with actual operating mode, and causing testing according to these model drawn also just has larger limitation.

Summary of the invention

(1) technical matters that will solve

The object of this invention is to provide a kind of battery capacity online test method, with overcome cannot be simple and reliable in prior art calculate the capacity of electric battery, reduce the defect of car load continual mileage.

(2) technical scheme

To achieve these goals, the invention provides a kind of battery capacity online test method, it specifically comprises:

T1 moment initial start-up vehicle, detects the open-circuit voltage OCV1 of electric battery this moment, and according to open-circuit voltage OCV1, obtains the SOC SOC1 of electric battery this moment;

The t2 moment starts vehicle again, detects the open-circuit voltage OCV2 of electric battery this moment, and according to open-circuit voltage OCV2, obtains the SOC SOC2 of electric battery this moment;

The current capacity C of electric battery is calculated by formula (1):

$C=\left|\frac{Q}{\mathrm{soc}1-\mathrm{soc}2}\right|---\left(1\right)$

Wherein, Q is the charge value that in t1 and the t2 time interval, electric battery carries out discharge and recharge.

Preferably, the t1 moment, according to open-circuit voltage OCV1, show that the SOC SOC1 of electric battery this moment obtains especially by formula (2):

$\mathrm{SOC}1=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}1-{\mathrm{OCV}}^{\′})---\left(2\right)$

Wherein, OCV ' and OCV " be respectively predetermined upper limit value interval belonging to OCV1 and lower limit;

SOC ' is the higher limit of the SOC of the electric battery corresponding with OCV ';

SOC " be and OCV " lower limit of the SOC of corresponding electric battery;

Described OCV ', OCV ", SOC ' and SOC " be calibration value in advance.

Preferably, the t2 moment, according to open-circuit voltage OCV2, show that the SOC SOC2 of electric battery this moment obtains especially by formula (3):

$\mathrm{SOC}2=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}2-{\mathrm{OCV}}^{\′})---\left(3\right)$

Wherein, OCV ' and OCV " be respectively predetermined upper limit value interval belonging to OCV2 and lower limit;

SOC ' is the higher limit of the SOC of the electric battery corresponding with OCV ';

SOC " be and OCV " lower limit of the SOC of corresponding electric battery;

Described OCV ', OCV ", SOC ' and SOC " be calibration value in advance.

Preferably, the charge value Q of described discharge and recharge can be drawn by formula (4):

$Q=\frac{{\∫}_{t1}^{t2}\mathrm{\ηidt}}{3600}---\left(4\right)$

Wherein: η is the coulombic efficiency of electric battery, i is the electric current of electric battery.

Preferably, the open-circuit voltage OCV of described battery is the voltage of battery under open-circuit condition.

Preferably, described voltage under open-circuit condition is that charging and discharging currents amount is less than threshold value and leaves standstill the voltage exceeded under certain hour state under uniform temperature and air pressure conditions.

Preferably, described temperature range is-30 DEG C ~ 60 DEG C, and time of repose is 10 minutes ~ 12 hours.

(3) beneficial effect

Battery capacity online test method provided by the invention, guarantees, when vehicle normally runs, simply, effectively, reliably to calculate the capacity of electric battery, guarantees the continual mileage of vehicle.

Accompanying drawing explanation

Fig. 1 is embodiment of the present invention battery capacity online test method principle schematic;

Fig. 2 is embodiment of the present invention battery capacity online test method process flow diagram.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples for illustration of the present invention, but are not used for limiting the scope of the invention.

As depicted in figs. 1 and 2, the embodiment of the present invention provides a kind of battery capacity online test method, and it specifically comprises:

Step S1, t1 moment initial start-up vehicle, detect the open-circuit voltage OCV(Open Circuit Voltage of battery this moment) 1, and according to open-circuit voltage OCV1, draw the SOC SOC1 of electric battery this moment;

Concrete, shelve after static state shelves certain hour at vehicle, the moment of vehicle is started in the t1 moment, by BMS(battery management system, Battery Management System) the open-circuit voltage OCV1 of battery can be directly detected, and the SOC SOC1 of current battery group is drawn according to open-circuit voltage OCV1.

It should be noted that, in the present embodiment, the open-circuit voltage OCV of battery is the voltage of battery under open-circuit condition.Voltage under concrete open-circuit condition refers to charging and discharging currents under uniform temperature and air pressure conditions and is less than threshold value and leaves standstill the voltage exceeded under certain hour state.

In actual applications, this temperature range refers to battery operated scope, namely-30 DEG C ~ 60 DEG C, and air pressure conditions is for should (determine with different monomers design) not cause battery cell safety valve to be opened for, this charging and discharging currents is less than threshold value, and this threshold value can be determined according to concrete vehicle, and more excellent situation is charging and discharging currents is 0, and time of repose is 10 minutes ~ 12 hours, such as, can select 20 minutes, 30 minutes, 2 hours, 5 hours etc.

Step S2, t2 moment start vehicle again, detect the open-circuit voltage OCV2 of battery this moment, and according to open-circuit voltage OCV2, draw the SOC SOC2 of electric battery this moment;

Concrete, vehicle, after operation after a while, needs standing a period of time, starts moment in another t2 moment, the open-circuit voltage OCV2 of current time battery detected by BMS, and draw the SOC SOC2 of current battery group according to open-circuit voltage OCV2.

The current capacity C of step S3, electric battery is calculated by formula (1):

$C=\left|\frac{Q}{\mathrm{soc}1-\mathrm{soc}2}\right|---\left(1\right)$

Wherein, Q is the charge value that in t1 and the t2 time interval, electric battery carries out discharge and recharge.

Because the open-circuit voltage OCV of electric battery is relative clear and definite with the corresponding relation between state-of-charge SOC, therefore, the state-of-charge of electric battery can be drawn easily by OCV according to homologous thread, and the computational accuracy of accumulation discharge and recharge is also higher, therefore, capacity after cell decay obtains according to the method the level that its error can reach lower, and then simply, effectively, reliably can calculate the capacity of electric battery, guarantees the continual mileage of vehicle.

Concrete, in step S1, according to open-circuit voltage OCV1, show that the SOC SOC2 of electric battery this moment obtains especially by formula (2):

Record the open-circuit voltage OCV1 value of t1 moment battery, the value of described OCV1 substituted in formula (2):

$\mathrm{SOC}1=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}1-{\mathrm{OCV}}^{\′})---\left(2\right)$

Wherein, OCV ' and OCV " be respectively predetermined upper limit value interval belonging to OCV1 and lower limit;

SOC ' is the higher limit of the SOC of the electric battery corresponding with OCV ';

SOC " for OCV " corresponding to the lower limit of SOC of electric battery;

Described OCV ', OCV ", SOC ' and SOC " be calibration value.

Wherein, it should be noted that, the respective value between this SOC ~ OCV is the calibration value of electric battery when dispatching from the factory, and a certain specific model battery has the specific SOC ~ OCV corresponding calibration value corresponding with it.

As shown in table 1, be the 35Ah battery that the solid profit of alliance of CITIC Guoan is produced, model is the corresponding calibration value of SOC ~ OCV of SPIM14245190.

Table 1

SOC%	100	95	90	85	80	75	70	65	60	55	50
												OCV	4.173	4.113	4.085	4.068	4.053	4.038	4.017	3.994	3.968	3.935	3.915
SOC%	45	40	35	30	25	20	15	10	5	0
												OCV	3.898	3.881	3.861	3.84	3.811	3.707	3.649	3.598	3.545	3.417

As shown in table 2, be the 60Ah battery that Beijing Pride New Energy Battery Technology Co., Ltd. produces, model is the corresponding calibration value of SOC ~ OCV of 29/135/220.

Table 2

SOC%	100	95	90	85	80	75	70	65	60	55	50
												OCV	3.449	3.338	3.336	3.334	3.333	3.331	3.331	3.31	3.296	3.293	3.291
SOC%	45	40	35	30	25	20	15	10	5	0
												OCV	3.29	3.289	3.286	3.272	3.256	3.24	3.218	3.202	3.123	2.692

Reference table 1, is OCV1=4.040 as recorded t1 moment open-circuit voltage, then substitutes in following formula by this value:

$\mathrm{SOC}1=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}1-{\mathrm{OCV}}^{\′})$

Wherein, due to OCV1=4.040, then the regional extent fallen into is 4.053 ~ 4.038, therefore, and OCV '=4.053, OCV "=4.038; And SOC '=80%, SOC "=75%, by calculating SOC1=75.7%.

If the OCV1 recorded just in time drops on the endpoint value of OCV in table, then SOC value directly can obtain by tabling look-up.If record OCV1=4.017, so directly obtain SOC=70%.

Certainly, the SOC2 in t2 moment adopts said method to obtain, and does not repeat them here.

Certainly, the value of this SOC1 and SOC2, except adopting said method and obtaining, also can adopt other existing modes to obtain.

Wherein, the charge value Q of discharge and recharge can be drawn by formula (3):

$Q=\frac{{\∫}_{t1}^{t2}\mathrm{\ηidt}}{3600}---\left(4\right)$

Wherein: η is the coulombic efficiency of electric battery, i is the electric current of electric battery.

Certainly, except the charge value Q adopting the integral way in the present embodiment to calculate discharge and recharge, other modes in prior art can also be adopted to obtain.

Because the speed of the capacity attenuation of battery or change is very slow, as long as there is leaving standstill for twice operating mode just can be used for the decay capacity of estimating battery, convenient enforcement, therefore, the present invention can when not affecting the capacity obtaining present battery vehicle normally runs.

Foregoing description provides in order to example with for the purpose of describing, and is not exhaustively or limit the invention to disclosed form.Many modifications and variations are obvious for the ordinary skill in the art.Selecting and describing embodiment is in order to principle of the present invention and practical application are better described, and enables those of ordinary skill in the art understand the present invention thus design the various embodiments with various amendment being suitable for special-purpose.

Claims (7)

1. a battery capacity online test method, is characterized in that, comprising:

T1 moment initial start-up vehicle, detects the open-circuit voltage OCV1 of electric battery this moment, and according to open-circuit voltage OCV1, obtains the SOC SOC1 of electric battery this moment;

The t2 moment starts vehicle again, detects the open-circuit voltage OCV2 of electric battery this moment, and according to open-circuit voltage OCV2, obtains the SOC SOC2 of electric battery this moment;

The current capacity C of electric battery is calculated by formula (1):

$C=\left|\frac{Q}{\mathrm{soc}1-\mathrm{soc}2}\right|---\left(1\right)$

Wherein, Q is the charge value that in t1 and the t2 time interval, electric battery carries out discharge and recharge.

2. online test method as claimed in claim 1, it is characterized in that, the t1 moment, according to open-circuit voltage OCV1, show that the SOC SOC1 of electric battery this moment obtains especially by formula (2):

$\mathrm{SOC}1=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}1-{\mathrm{OCV}}^{\′})---\left(2\right)$

Wherein, OCV ' and OCV " be respectively predetermined upper limit value interval belonging to OCV1 and lower limit;

SOC ' is the higher limit of the SOC of the electric battery corresponding with OCV ';

SOC " be and OCV " lower limit of the SOC of corresponding electric battery;

Described OCV ', OCV ", SOC ' and SOC " be calibration value in advance.

3. online test method as claimed in claim 1, it is characterized in that, the t2 moment, according to open-circuit voltage OCV2, show that the SOC SOC2 of electric battery this moment obtains especially by formula (3):

$\mathrm{SOC}2=\frac{{\mathrm{SOC}}^{\′\′}-{\mathrm{SOC}}^{\′}}{{\mathrm{OCV}}^{\′\′}-{\mathrm{OCV}}^{\′}}(\mathrm{OCV}2-{\mathrm{OCV}}^{\′})---\left(3\right)$

Wherein, OCV ' and OCV " be respectively predetermined upper limit value interval belonging to OCV2 and lower limit;

SOC ' is the higher limit of the SOC of the electric battery corresponding with OCV ';

SOC " be and OCV " lower limit of the SOC of corresponding electric battery;

Described OCV ', OCV ", SOC ' and SOC " be calibration value in advance.

4. online test method as claimed in claim 1, is characterized in that, the charge value Q of described discharge and recharge can be drawn by formula (4):

$Q=\frac{{\∫}_{t1}^{t2}\mathrm{\ηidt}}{3600}---\left(4\right)$

Wherein: η is the coulombic efficiency of electric battery, i is the electric current of electric battery.

5. online test method as claimed in claim 1, it is characterized in that, the open-circuit voltage OCV of described battery is the voltage of battery under open-circuit condition.

6. online test method as claimed in claim 5, is characterized in that, described voltage under open-circuit condition is that charging and discharging currents amount is less than threshold value and leaves standstill the voltage exceeded under certain hour state under uniform temperature and air pressure conditions.

7. online test method as claimed in claim 6, it is characterized in that, described temperature range is-30 DEG C ~ 60 DEG C, and time of repose is 10 minutes ~ 12 hours.