Lithium battery optimizes charging current preparation method
Technical field
The invention belongs to lithium battery charging technique fields.
Background technique
Lithium battery is constant-current constant-voltage charging method using most charging methods at present, is filled first to battery with constant current
Electricity terminates when Mr. Yu's value small to charging current using constant-voltage charge after cell voltage reaches certain value.Such charging method letter
It list and is easy to control, but the selection of constant-current phase charging current is substantially obtained by experience, to energy loss in battery itself
Influence with the charging time is uncertain.
The main reason for battery itself energy loss is battery-heating, battery-heating easily cause battery thermal runaway;And it fills
Electric overlong time is to restrict one of an important factor for battery is promoted the use of.Usual charging current increases, and the charging time becomes smaller, and electric
The energy loss in pond itself will increase, this is a conflicting problem.
Summary of the invention
The present invention is to solve existing lithium battery charging current and increase, and the charging time reduces, and battery itself loss increases
Big problem now provides the optimal charging current preparation method of lithium battery based on charging time Yu battery itself energy loss.
The optimal charging current preparation method of lithium battery based on charging time Yu battery itself energy loss,
It the described method comprises the following steps:
Charging process partiting step: charging process is divided into N number of charging stage, wherein the propagation process of SOC from 0 to 1
In, every increase p%SOC is a charging stage;
Model foundation step: the single order RC equivalent-circuit model of lithium battery is established, which includes following parameter: controlled electricity
Potential source, the internal resistance of cell, polarization resistance and polarization capacity;
Boundary condition determines step: the ginseng of single order RC equivalent-circuit model in each charging stage is determined using charging experiment
The boundary condition that several and charging current is chosen;
Objective function establishment step: it establishes using charging time in entire charging process and battery itself energy loss as object
Objective function f:
Wherein, IjIt is the charging current of j-th of charging stage, Rj(Ij) it be j-th of charging stage in charging current is IjWhen
Internal resistance resistance value, △jIt is the charging time of j-th of charging stage, W1jIt is the energy damage in j-th of charging stage in polarization resistance
Consumption;
Optimal current obtains step: being optimized using dynamic programming algorithm to objective function f, obtains objective function most
Small value obtains the optimal charging current of each charging stage.
The present invention is with the maximum charging current of battery under different SOC (preestimating battery state-of-charge, State of Charge)
For boundary condition, using in entire charging process charging time and battery itself energy loss as object construct objective function, adopt
Objective function is optimized with dynamic programming algorithm, to obtain making being based on charging time and battery in entire charging process certainly
The optimal charging current of body loss.
A kind of optimal charging current acquisition side based on lithium battery charging time and self-energy loss of the present invention
Method is related to battery boosting technology field, using the maximum charging current of battery under different SOC levels as boundary condition, comprehensively considers
Battery charge time and the two conflicting aspects of battery itself energy loss, building are the mesh of object with the two aspects
Scalar functions.Further charging process is walked for 5% point with the every variation of SOC for N, using dynamic programming algorithm, forward from final step
It calculates, obtains the electric current of each step charging process, so that entire charging process be made to be optimal, battery itself loss and constant current are permanent
Pressure charging method, which is compared, reduces 5%.
Detailed description of the invention
Fig. 1 is the process based on charging time Yu the optimal charging current preparation method of lithium battery of battery itself energy loss
Workflow graph;
Fig. 2 is the corresponding single order RC equivalent-circuit model schematic diagram of each charging stage battery;
Fig. 3 is the flow chart of charging experiment;
Fig. 4 is the method flow diagram optimized using dynamic programming algorithm to objective function f;
Fig. 5 is the optimal charging current curve schematic diagram obtained after optimization.
Specific embodiment
Specific embodiment 1: referring to Fig.1, Fig. 2 and Fig. 5 illustrate present embodiment, base described in present embodiment
In the optimal charging current preparation method of lithium battery in charging time and battery itself energy loss, comprising the following steps:
Charging process partiting step: charging process is divided into N number of charging stage, wherein the propagation process of SOC from 0 to 1
In, every increase p%SOC is a charging stage;
Model foundation step: the single order RC equivalent-circuit model of lithium battery is established, which includes following parameter: controlled electricity
Potential source, the internal resistance of cell, polarization resistance and polarization capacity;
Boundary condition determines step: the ginseng of single order RC equivalent-circuit model in each charging stage is determined using charging experiment
The boundary condition that several and charging current is chosen;
Objective function establishment step: it establishes using charging time in entire charging process and battery itself energy loss as object
Objective function f:
Wherein, IjIt is the charging current of j-th of charging stage, Rj(Ij) it be j-th of charging stage in charging current is IjWhen
Internal resistance resistance value, △jIt is the charging time of j-th of charging stage, W1jIt is the energy damage in j-th of charging stage in polarization resistance
Consumption;
Optimal current obtains step: being optimized using dynamic programming algorithm to objective function f, obtains objective function most
Small value obtains the optimal charging current of each charging stage.
Specific embodiment 2: present embodiment be to described in specific embodiment one based on charging time and battery from
The optimal charging current preparation method of the lithium battery of body energy loss is described further, and in present embodiment, utilizes following methods
Determine the boundary condition that the parameter and charging current of single order RC equivalent-circuit model in each charging stage are chosen:
In each charging stage, rate of charge is since 0.1C (C indicates battery rated capacity), the every increase of rate of charge
0.1C carries out primary charging experiment, and until rate of charge reaches lithium battery permission maximum charge multiplying power, it is real to carry out X charging altogether
It tests, obtains the parameter and X maximum charging current of X group single order RC equivalent-circuit model, X maximum charging current is fitted to one
Current curve, the boundary condition which is chosen as the charging current of current charging stage.
Specific embodiment 3: illustrating present embodiment referring to Fig. 3, present embodiment is to specific embodiment two
Described is described further based on charging time and the optimal charging current preparation method of lithium battery of battery itself energy loss,
In present embodiment, before charging experiment, charging experimentation is divided into M experimental stage first, wherein SOC's from 0 to 1
In propagation process, every increase q%SOC is an experimental stage,
Charging experiment the following steps are included:
Step 11: to static 5min after lithium battery charging 10s, obtaining the single order RC equivalent circuit mould of i-th of experimental stage
Shape parameter, wherein the initial value of i is 1, then executes step 12;
Step 12: charging to lithium battery, and judge whether lithium battery voltage is greater than charge cutoff voltage, be to then follow the steps
16, it is no to then follow the steps 13;
Step 13: judging whether lithium battery charging capacity is more than or equal to i × q%SOC, be, make i=i+1, then execute
Step 14, otherwise return step 12;
Step 14: judge whether i is greater than M, is to then follow the steps 16, it is no to then follow the steps 15;
Step 15: by the static 3h of lithium battery, then return step 11;
Step 16: terminating charging experiment, and be that current charging is real by maximum charging current corresponding to lithium battery SOC at this time
The maximum charging current tested.
In present embodiment, a charging experiment can obtain the single order RC equivalent circuit model parameter of M experimental stage
With the maximum charging current of a charging experiment.In each experimental stage, rate of charge is the rate of charge of current charging stage.
Specific embodiment 4: present embodiment be to described in specific embodiment three based on charging time and battery from
The optimal charging current preparation method of the lithium battery of body energy loss is described further, and in present embodiment, obtains i-th of experiment
The single order RC equivalent circuit model parameter in stage specifically:
Parameter identification is carried out with nonlinear least square method, obtains the single order RC equivalent-circuit model of i-th of experimental stage
Parameter.
Specific embodiment 5: present embodiment be to described in specific embodiment one based on charging time and battery from
The optimal charging current preparation method of the lithium battery of body energy loss is described further, in present embodiment, j-th of charging stage
Charging time △jIt is obtained by following formula:
Wherein, s (j) is the SOC level of j-th of charging stage, and cap is the rated capacity of lithium battery, unit Ah.
Specific embodiment 6: present embodiment be to described in specific embodiment one based on charging time and battery from
The optimal charging current preparation method of the lithium battery of body energy loss is described further, in present embodiment, j-th of charging stage
Energy loss W in interior polarization resistance1jIt is obtained by following formula:
Wherein, △ is the sampling time, and α is the number of samples of j-th of charging stage, R1j(Ij) and C1j(Ij) it is respectively jth
A charging stage polarization resistance value and polarization capacity value, U1jFor the voltage on j-th of charging stage initial time polarization capacity.
In present embodiment, firstly, set in j-th of charging stage each sampling time as △, then j-th charging stage
Number of samples α are as follows:
The then energy loss W in j-th of charging stage in polarization resistance1jAre as follows:
For the charging current of j-th of charging stage any sampling instant k, expression formula are as follows:
Therefore, W1jIt can rewrite are as follows:
It was influenced by a upper charging stage, the voltage of each charging stage initial time of polarization capacity was a upper charging stage
The voltage at end moment fills to express polarization capacity in the voltage of each charging stage initial time using from the last one
The method of recursion forward of electric stage.Due to the charging current very little of the last one charging stage, the charging time is relatively long, therefore
Think the electric current I in the last moment polarization resistance of the last one charging stageNHave reached stable state:
Wherein, I1NMIt is the electric current in last last moment charging stage polarization resistance, △NFor the last one charging stage
Charging time, R1N(IN) it be the last one charging stage polarization resistance in electric current is INWhen resistance value, C1N(IN) it is last
A charging stage polarization capacity is I in electric currentNWhen capacitance, U1NFor on the last one charging stage initial time polarization capacity
Voltage;
It can be concluded that the voltage U on the last one charging stage initial time polarization capacity1N, and at this time on polarization capacity
Voltage was the voltage at a upper end moment charging stage again:
I1(N-1)MFor the electric current in the N-1 last moment charging stage polarization resistance, R1(N-1)It is the N-1 charging rank
Section polarization resistance is I in electric currentN-1When resistance value, IN-1For the charging current of the N-1 charging stage, U1(N-1)It is filled for N-1
Voltage on electric stage initial time polarization capacity, R1(N-1)(IN-1) it be the N-1 charging stage polarization resistance in electric current is IN-1
When resistance value, C1(N-1)(IN-1) it be the N-1 charging stage polarization capacity in electric current is IN-1When capacitance, △(N-1)For N-
The charging time of 1 charging stage.
It can be concluded that voltage of the polarization capacity in the N-1 charging stage initial time.By constantly recursion back to front,
Voltage U of the available polarization capacity in the initial time of each charging stage1j。
Specific embodiment 7: present embodiment be to described in specific embodiment one based on charging time and battery from
The optimal charging current preparation method of the lithium battery of body energy loss is described further, and in present embodiment, utilizes Dynamic Programming
The method that algorithm optimizes objective function f are as follows:
Step 21: making the initial value N of j, add a charging stage, it may be assumed that N+1 stage, and lithium battery self-energy
W is lostN+1(IN+1)=0, charging time TN+1(IN+1Then)=0 executes step 22,
Step 22: enabling
0<IN<INmax
0<IN-1<I(N-1)max
0<Ij<Ijmax
Wherein, IjmaxFor the boundary condition that j-th of charging stage charging current is chosen, j=1,2 ..., N.
Step 23: judge whether following formula is true:
Tj(Ij)=opt (△j+Tj+1)
Opt=min { Wj(Ij)Tj(Ij)}
It is to make j=j-1, then return step 22, no to then follow the steps 24,
In above formula, △ is sampling time, Rj(Ij) it be j-th of charging stage in charging current is IjWhen internal resistance resistance value,
I1jkFor the electric current of j-th of charging stage, k-th of charging moment polarization resistance, Wj(Ij) it is that j-th of charging stage initial time arrives
The energy loss of battery itself, T at the end of chargingj(Ij) it is j-th charging stage initial time to the time at the end of charging,
Tj+1For the time at the end of+1 charging stage initial time of jth to charging, opt indicates optimal;
Step 24: judging whether j is 1, be to complete to optimize, otherwise return step 22.