CN105738824A - Method for estimating residual capacity of battery - Google Patents

Abstract

The invention discloses a method for estimating the residual capacity of a battery, which sequentially comprises the following steps: calculating the residual capacity of the battery according to the charging and discharging current of the battery pack; if the standing state of the battery pack exceeds the preset time, detecting the open-circuit voltage OCV; calculating the variation of the residual capacity of the battery in each time period and calculating the variation of the residual capacity of the battery according to an open-circuit voltage lookup table; calculating a battery capacity attenuation weight value according to the two calculated variable quantities; and calculating the current battery residual capacity according to the weight value and the battery residual capacity at the previous moment. The method of the invention expresses the attenuation trend of the battery capacity through the weight value, introduces the weight value when calculating the residual battery capacity, and simultaneously carries out error correction, thereby realizing the accurate estimation of the residual battery capacity; the method updates the remaining capacity as long as the condition is met when the battery management system is operated. The method for estimating the residual capacity of the battery can be widely applied to the field of battery pack management.

Description

A kind of battery remaining power evaluation method

Technical field

The present invention relates to battery system management domain, especially a kind of battery remaining power evaluation method.

Background technology

In the battery management system of electric automobile, it is necessary to accurately estimate the residual capacity (SOC) of battery bag.Only know the Expenditure Levels of current electric quantity such that it is able to estimate out vehicle and can travel the mileage continuing to travel.If, it is impossible to accurately may there is battery bag and cross the danger putting monomer in estimation SOC, causes that battery bag monomer is too low causes irreversible injury to battery itself, thus battery life is produced a very large impact.It will be seen that to fill how many electricity when accurately estimating SOC, it is possible to release how many electricity.How much gasoline can have been added, it is possible to estimate how far vehicle can travel accurately as conventional gasoline car is the same.

Accurately estimate that SOC needs the strict total capacity known in the fully charged situation of battery bag under normal circumstances.But user uses the capacity situation that electric automobile has then been difficult to electrolytic cell bag accurate.Even in test chamber in test battery capacity situation, the initial capacity of battery is affected by various factors: the duration that dispatches from the factory of battery core, the charge and discharge cycles number of times of battery core, temperature etc..Still can not well judge the SOC of battery from these factors, it has a problem in that the high temperature storage life-span considering battery, cell load situation, depth of discharge, charge-discharge magnification etc..Can accurately not estimate SOC, it is likely that cause that battery is constantly in big load, when big depth of discharge, the life-span of battery is had a significant impact.

Summary of the invention

In order to solve above-mentioned technical problem, it is an object of the invention to: a kind of method for accurately estimating the battery remaining power being in running status is provided.

The technical solution adopted in the present invention is: a kind of battery remaining power evaluation method, includes following steps:

A, calculate battery remaining power SOC (Ah) according to the charging and discharging currents of battery bag；

If B battery bag static condition exceedes the scheduled time, then detection open-circuit voltage OCV；

C, calculate the variation delta SOC (Ah) of battery remaining power in each time cycle and the variation delta SOC (ocv) according to open-circuit voltage computation of table lookup battery remaining power；

D, calculate battery capacity decaying weight value W according to two variable quantities calculated in step C；

E, calculate present battery residual capacity according to the battery remaining power of battery capacity decaying weight value W and previous moment.

Further, described step A adopts Current integrating method to calculate the battery capacity used according to charging and discharging currents, and calculates battery remaining power.

Further, the static condition in described step B is that the absolute value of electric current output is less than 1A.

Further, in described step D, the computational methods of battery capacity decaying weight value W are:

$W=1-K_1\frac{100SOC{\left(Ah\right)}_{Error}}{\mathrm{\Δ}SOC\left(Ah\right)}+K_2\frac{100SOC{\left(ocv\right)}_{Error}}{\mathrm{\Δ}SOC\left(ocv\right)}+K_{3}SOC{\left(ocv\right)}_{ErrorP},$

Wherein, K₁、K₂、K₃It is side-play amount constant, SOC (Ah)_ErrorFor battery cell voltage measurement error, SOC (ocv)_ErrorFor battery cell open-circuit voltage error, SOC (ocv)_ErrorPBattery cell open-circuit voltage error for upper a period of time.

Further, described battery cell voltage measurement error SOC (Ah)_ErrorComputational methods be:

SOC(Ah)_Error=∫ (gI+k) dt,

Wherein, g is current error gain, and I is charging and discharging currents, and k is side-play amount.

Further, in described step E, present battery residual capacity SOC (Ah)_presentComputational methods be:

SOC(Ah)_present=1-(battery capacity of use/battery system total capacity),

Wherein, the described battery capacity used adopts Ah integration method to calculate according to the charging and discharging currents of battery bag, and described battery bag total capacity is the battery bag total capacity product with battery capacity decaying weight value W of previous time period.

The invention has the beneficial effects as follows: the attenuation trend of battery capacity is showed by weighted value by the inventive method, and introduce this weighted value when the calculating of remaining battery capacity, calculating process carries out error correction, thus realizing the accurate estimation to battery remaining power；As long as the method is the eligible renewal just carrying out residual capacity when battery management system runs.

Accompanying drawing explanation

Fig. 1 is the total flow chart of steps of the inventive method；

Fig. 2 is battery management system structured flowchart of the present invention.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described further:

With reference to Fig. 1, a kind of battery remaining power evaluation method, include following steps:

A, calculate battery remaining power SOC (Ah) according to the charging and discharging currents of battery bag；

If B battery bag static condition exceedes the scheduled time, then detection open-circuit voltage OCV；

C, calculate the variation delta SOC (Ah) of battery remaining power in each time cycle and the variation delta SOC (ocv) according to open-circuit voltage computation of table lookup battery remaining power；

D, calculate battery capacity decaying weight value W according to two variable quantities calculated in step C；

E, calculate present battery residual capacity according to the battery remaining power of battery capacity decaying weight value W and previous moment.

Battery management system structure, as in figure 2 it is shown, include battery bag (or single battery), is obtained battery bag current information by temperature sensor, voltage sensor, current sensor, enters in MCU processor after being changed by ADC.Processor MCU external clock circuit, display device and storage device.

It is further used as preferred embodiment, described step A adopts Current integrating method to calculate the battery capacity used according to charging and discharging currents, and calculates battery remaining power.

Current integrating method obtains battery system current size by current sensor, then periodic electric current and time value product accumulation are obtained, following I (t1) * t1+I (t2) * (t2-t1) ... I (tn) * (tn-t (n-1)).In order to ensure the accuracy of integration, period of time T is typically in below 100ms, i.e. t1=t2-t1=...=(tn-t (n-1)) < 100ms.I (tn) is tn moment current value.

Being further used as preferred embodiment, the static condition in described step B is that the absolute value of electric current output is less than 1A.

Thinking that battery bag is in static condition when current value is less than certain threshold values time, such as vehicle is in halted state does not have powerful device to use, and electric current output absolute value is less than 1A, it is believed that battery bag is in static condition.The setting of threshold values is determined on a case-by-case basis, and is construed as static condition under the current conditions less on the impact of battery bag.

After the time of repose sufficiently long time, carry out OCV calculating by battery bag monomer voltage.SOC (Ah)=SOC (Ah) is calculated by t1 and the t2 moment_t1-SOC(Ah)_t2；By t1 and t2 moment SOC (ocv)=SOC (ocv)_t1-SOC(ocv)_t2。

Being further used as preferred embodiment, in described step D, the computational methods of battery capacity decaying weight value W are:

$W=1-K_1\frac{100SOC{\left(Ah\right)}_{Error}}{\mathrm{\&Delta;}SOC\left(Ah\right)}+K_2\frac{100SOC{\left(ocv\right)}_{Error}}{\mathrm{\&Delta;}SOC\left(ocv\right)}+K_{3}SOC{\left(ocv\right)}_{ErrorP},$

Wherein, K1, K2, K3 are side-play amount constant, SOC (Ah)_ErrorFor battery cell voltage measurement error, SOC (ocv)_ErrorFor battery cell open-circuit voltage error, SOC (ocv)_ErrorPBattery cell open-circuit voltage error for upper a period of time.

SOC(ocv)_ErrorFor battery cell voltage measurement error, this error causes that OCV tables look-up generation error, the source that this difference produces mainly includes following aspect: the time of repose length of battery, moment temperature conditions before standing, and before standing, moment temperature conditions directly results in the time length required for battery cell depolarization.Such as in 0 DEG C of situation, the time required for depolarization, monomer voltage measurement error at this time was less more than 4 hours；In 30 DEG C of situations, the time required for depolarization is comparatively short.If depolarization is incomplete, then SOC (ocv) Error error amount is more high；In practice process, it is necessary to carry out Experimental Calibration by battery bag.

Weighted value introduces battery cell open-circuit voltage error SOC (ocv) of upper a period of time in calculating_ErrorPIt is to prevent OCV Watch Error from making SOC (ocv) when relatively larger_ErrorWeight accounting excessive.

It is further used as preferred embodiment, described battery cell voltage measurement error SOC (Ah)_ErrorComputational methods be:

SOC(Ah)_Error=∫ (gI+k) dt,

Wherein, g is current error gain, and I is charging and discharging currents, and k is current measurement errors side-play amount；Above-mentioned side-play amount constant K1, K2, K3 and k require over demarcation in practice process and obtain.

It is further used as preferred embodiment, in described step E, present battery residual capacity SOC (Ah)_presentComputational methods be:

SOC(Ah)_present=1-(battery capacity of use/battery system total capacity),

Wherein, the described battery capacity used adopts Ah integration method to calculate according to the charging and discharging currents of battery bag, and described battery bag total capacity is the battery bag total capacity product with battery capacity decaying weight value W of previous time period.

It is above the preferably enforcement of the present invention has been illustrated, but the invention is not limited to described embodiment, those of ordinary skill in the art can also make all equivalents or replacement under the premise without prejudice to spirit of the present invention, and these equivalent deformation or replacement are all contained in the application claim limited range.

Claims (6)

1. a battery remaining power evaluation method, it is characterised in that: include following steps:

A, calculate battery remaining power SOC (Ah) according to the charging and discharging currents of battery bag；

If B battery bag static condition exceedes the scheduled time, then detection open-circuit voltage OCV；

C, calculate the variation delta SOC (Ah) of battery remaining power in each time cycle and the variation delta SOC (ocv) according to open-circuit voltage computation of table lookup battery remaining power；

D, calculate battery capacity decaying weight value W according to two variable quantities calculated in step C；

E, calculate present battery residual capacity according to the battery remaining power of battery capacity decaying weight value W and previous moment.

2. a kind of battery remaining power evaluation method according to claim 1, it is characterised in that: described step A adopts Current integrating method to calculate the battery capacity used according to charging and discharging currents, and calculates battery remaining power.

3. a kind of battery remaining power evaluation method according to claim 1, it is characterised in that: the static condition in described step B is that the absolute value of electric current output is less than 1A.

4. a kind of battery remaining power evaluation method according to claim 1, it is characterised in that: in described step D, the computational methods of battery capacity decaying weight value W are:

$W=1-K_1\frac{100SOC{\left(Ah\right)}_{Error}}{\mathrm{\&Delta;}SOC\left(Ah\right)}+K_2\frac{100SOC{\left(ocv\right)}_{Error}}{\mathrm{\&Delta;}SOC\left(ocv\right)}+K_{3}SOC{\left(ocv\right)}_{ErrorP},$

Wherein, K₁、K₂、K₃It is side-play amount constant, SOC (Ah)_ErrorFor battery cell voltage measurement error, SOC (ocv)_ErrorFor battery cell open-circuit voltage error, SOC (ocv)_ErrorPBattery cell open-circuit voltage error for upper a period of time.

5. a kind of battery remaining power evaluation method according to claim 4, it is characterised in that: described battery cell voltage measurement error SOC (Ah)_ErrorComputational methods be:

SOC(Ah)_Error=∫ (gI+k) dt,

Wherein, g is current error gain, and I is charging and discharging currents, and k is side-play amount.

6. a kind of battery remaining power evaluation method according to claim 1, it is characterised in that: in described step E, present battery residual capacity SOC (Ah)_presentComputational methods be:

SOC(Ah)_present=1-(battery capacity of use/battery system total capacity),

Wherein, the described battery capacity used adopts Ah integration method to calculate according to the charging and discharging currents of battery bag, and described battery bag total capacity is the battery bag total capacity product with battery capacity decaying weight value W of previous time period.