Device and method for determining characteristic variables for batteries

• US 20050189948A1
• Filed: 02/04/2005
• Published: 09/01/2005
• Est. Priority Date: 02/04/2004
• Status: Active Grant

• Current Assignee: VB Autobatterie GmbH & Co. KGaA (Robert Bosch GmbH)
• Original Assignee: VB Autobatterie GmbH
• Inventors: Koch, Ingo
• Granted Patent: US 7,327,147 B2
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/3828 using current integration

Abstract

A method for determination of characteristic variables for electrical states of an energy storage battery has the following steps:

• a) the electrolyte volume (v) of the energy storage battery is subdivided into at least two electrolyte volume components (v_i) with associated electrolyte balancing areas (S_i);
• b) at least two electrode plate balancing areas (P_k) are defined by subdividing the total resistance (R^M) of the electrode plates in the energy storage battery into resistance components (R_k^M) for the defined electrode plate balancing areas (P_k), and the total energy storage capacity (K^M) of the electrode plates in the energy storage battery into energy storage capacity components (K_k^M) for the defined electrode plate balancing areas (P_k);
• c) the electrolyte concentration (r_i) of the electrolyte volume components (v_i) for the defined electrolyte balancing areas (S_i) is determined;
• d) the amounts of charge (KE_k^M) which are in each case held in the electrode plates in the electrode plate balancing areas (P_k) are determined; and
• e) at least one characteristic variable is determined for associated electrical states of the energy storage battery by means of a mathematical model for describing an electrical equivalent circuit at least by means of the variables of the resistance components (R_k^M), of the energy storage capacity components (K_k^M), of the electrolyte concentration (r_i) and of the amounts of charge (KE_k^M) held.

Claims

1. Method for determination of characteristic variables for electrical states of an energy storage battery, having the following steps:

a) Subdividing the electrolyte volume (v) of the energy storage battery into at least two electrolyte volume components (v_i) with associated electrolyte balancing areas (S_i);

b) Defining of at least two electrode plate balancing areas (P_k) by subdividing the total resistance (R^M) of the electrode plates in the energy storage battery into resistance components (R_k^M) for the defined electrode plate balancing areas (P_k), and the total energy storage capacity (K^M) of the electrode plates in the energy storage battery into energy storage capacity components (K_k^M) for the defined electrode plate balancing areas (P_k);

c) Determining of the electrolyte concentration (r_i) of the electrolyte volume components (v_i) for the defined electrolyte balancing areas (S_i);

d) Determining of the amounts of charge (KE_k^M) which are in each case held in the electrode plates in the electrode plate balancing areas (P_k); and

e) Determining of at least one characteristic variable for associated electrical states of the energy storage battery by means of a mathematical model for describing an electrical equivalent circuit at least by means of the variables of the resistance components (R_k^M), of the energy storage capacity components (K_k^M), of the electrolyte concentration (r_i) and of the amounts of charge (KE_k^M) held.

2. Method according to claim 1, characterized in that the acid density of the electrolyte volume components (v_i) is a measure of the electrolyte concentration.

3. Method according to claim 1 or 2, characterized by the rest voltages (U_00k) being determined in the defined electrode plate balancing areas (P_k) as a function of the electrolyte concentration (r_i) in an associated electrolyte balancing area (S_i).

4. Method according to claim 3, characterized by the rest voltages (U_00k) also being determined in the defined electrode plate balancing areas (P_k) as a function of the battery temperature (T) and of the amounts of charge (KE_k^M) held.

5. Method according to one of the preceding claims, characterized by the currents (I_i) for the electrolyte balancing areas (S_i) being calculated from the total current (I) flowing to the connecting terminals of the energy storage battery and from a division ratio which is dependent on the electrolyte concentration (r_i) in the respective electrolyte balancing area (S_i).

6. Method according to one of the preceding claims, characterized by the currents (I_k) for the electrode plate balancing areas (P_k) being calculated from the total current (I) flowing to the connecting terminals of the energy storage battery and from a division ratio which is dependent on the rest voltage (U_00k) in the respective electrode plate balancing area (P_k) and the resistance components (R_k^M).

7. Method according to claim 6, characterized in that, for the discharge currents, the currents (I_i) for the electrolyte balancing areas (S_i) are assumed to be equal to the currents (I_k) calculated for the associated electrode plate balancing areas (P_k).

8. Method according to one of the preceding claims, characterized by the amount of charge (KE_k^M) held in an electrode plate balancing area (P_k) after a time period (dt) being calculated from the energy storage capacity (KE_k^M) held in this electrode plate balancing area (P_k) until immediately before this time period and the charge (I_k^M×

dt) which has flowed through the electrode plate balancing area (P_k) in the time period (dt);

KE_k^M(t₁+dt)=KE_k^M(t₁)+I_k^M·

dt.

9. Method according to one of the preceding claims, characterized by the amount of charge (RK_k^M) which can still be drawn from the electrode plates in the individual electrode plate balancing areas (P_k) being calculated from the energy storage capacity component (K_k^M) of the respective electrode plate balancing area (P_k) minus the amount of charge (KE_k^M) which was drawn from the active mass in the electrode plate balancing area (P_k) prior to the time period (dt), and minus the charge (I_k^M×

dt) drawn from the electrode plates in the electrode plate balancing area (P_k) in the time period (dt).

10. Method according to one of the preceding claims, characterized by the amounts of charge (RK_i^s) which can still be drawn from the electrolyte volume components (V_i) in the individual electrolyte balancing areas (S_i) being calculated as a function of the electrolyte concentration (r_i) at that time and the electrolyte volume (v_i) in the respective electrolyte balancing area (S_i) and the battery temperature (T).

11. Method according to one of the preceding claims, characterized by the remaining capacity (RK_g) which can still be drawn from the energy storage battery being calculated as a characteristic variable as a function of the amounts of charge (RK_k^M) which have been determined for the electrode plate balancing areas (P_k) and can still be drawn from the active masses of the respective electrode plate balancing areas (P_k), and as a function of the amounts of charge (RK_i^S) which have been determined for the electrolyte balancing areas (S_i) and can still be drawn from the electrolyte volume components (v_i) in the respective electrolyte balancing areas (S_i).

12. Method according to one of the preceding claims, characterized by the characteristic variable being determined as a function of the charge reversal current (I_U) on the electrode plates between points where the rest voltage (U_00,x) is relatively high and points where the rest voltage (U_00,y) is relatively low, with the charge reversal current (I_U) being calculated from the polarization resistance (R_p) on the electrode plate surfaces and the sum of the grid resistances (R_n) between the points (x, y), using the formula:

$I_U=\left(U_{00,x}-U_{00,y}\right)·<br><br>\left(R_{P,x}+R_{P,y}+\underset{n=x}{\overset{y}{\sum <br><br>}}<br><br>R_n\right)$

13. Method according to one of the preceding claims, characterized by the rest voltage (U_00,g) of the energy storage battery being calculated as a characteristic variable as a function of the state of charge of the individual electrode plate balancing areas (P_k), of the rest voltages (U_00,k) in the electrode plate balancing areas (P_k), of the resistance components (R_k^M) of the polarization resistance (R_p) and of the charge reversal current (I_U) by reversing the charge on in each case one individual electrode plate.

14. Method according to one of the preceding claims, characterized by the critical temperature (T_crit) for the start of ice crystal formation in the balancing areas being determined as a function of the electrolyte concentration (r_i) in the electrolyte balancing areas (S_i), the temperature (T) and the electrolyte volume components (v_i).

15. Method according to one of the preceding claims, characterized by the ice crystal volume (v_ice) in the electrolyte balancing areas (S_i) being determined from a defined relationship between the equilibrium concentration (CGG_i) of the acid in the electrolyte and the temperature (T) as well as the acid concentration (C_i) in the electrolyte using the formula:

v_ice,i′

=(1−

C_i/CGG_i)·

v_i.

16. Method according to claim 14 or 15, characterized by a characteristic variable for the performance of the energy storage battery being determined as a function of the proportion of the ice crystal volume (v_ice) to the electrolyte volume (v_i) in the electrolyte balancing areas (S_i) and the location (S_i) at which the ice crystal formation occurs.

17. Method according to one of the preceding claims, characterized by the state values for the electrolyte concentration (r_i) in the electrolyte balancing areas (S_i) being adapted as a function of the difference between the actual rest voltage (U₀₀) and the calculated rest voltage (U_00,g).

18. Method according to one of the preceding claims, characterized in that separate electrolyte balancing areas (S_i) are assigned to outer areas of the energy storage battery and are assessed separately from the other electrolyte balancing areas (S_i).

19. Monitoring device for an electrochemical energy storage battery having a measurement unit for measurement of the battery terminal voltage (U), of the battery terminal current (I) and of the battery temperature (T), and having an evaluation unit, characterized in that the evaluation unit is designed to carry out the method according to one of the preceding claims, preferably by programming of a microprocessor unit.