Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2002-05-28
2004-09-07
Le, N. (Department: 2858)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
C324S425000
Reexamination Certificate
active
06788068
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a method and device for measuring a pure resistance of an on-vehicle battery, which is mounted on a vehicle to supply electric power to loads in the vehicle.
(2) Description of the Related Art
In general, a battery can repeatedly be used within a range of its charging capacity by carrying out a charge which compensates a discharge thereof. However, when an unexpected event such as a deep discharge and lack of electrolyte takes place or even when the battery is used for a long period of time, repeated charges cause a rapid deterioration in chargeable capacity that corresponds to the electric power to be supplied to loads by discharge. Consequently, in a state that the chargeable capacity deteriorates as a result of the aging of the battery, an engine of a vehicle might not be started again when a starter motor is started after a stoppage of the engine, even if the discharge exceeding the charge takes place for a short period of time.
In this connection, when a new battery is compared with a battery in which the aging takes place, it is known that the latter has a pure resistance greater than that of the former. This is a reason why the measured pure resistance of a battery is a measure of replacing the battery when the vehicle is periodically inspected. By knowing the pure resistance, the degree of the deterioration of the battery can be defined taking the pure resistance and the polarization resistance component into consideration. When the pure resistance is determined, its value can be used to estimate the open circuit voltage of the battery.
In general, when current is discharged from a battery, it causes a voltage drop in the terminal voltage of the battery. The voltage drop is caused by an internal impedance (combined resistance) of the battery and is divided into a voltage drop due to IR loss (pure resistance, i.e. voltage drop due to ohmic resistance) caused by the structure of the battery and a voltage drop due to the polarization resistance component (activation polarization, concentration polarization) caused by a chemical reaction. As shown in
FIG. 11
, when a current-voltage characteristic (I-V characteristic) is computed, the voltage drop due to IR loss does not change provided that the battery state remains the same. On the other hand, the voltage drop resulting from the polarization resistance component changes depending upon the magnitude of the current and a period of the discharging time. When various states of the battery are estimated on the basis of the I-V characteristic including such a polarization resistance component, an accurate estimation cannot be obtained. This is a reason why a technique for measuring the pure resistance of the battery is necessary. The pure resistance can be obtained by separating the polarization resistance component out from the voltage drop in the terminal voltage of the battery.
As for an instrument generally used so far for measuring the pure resistance of a battery, the pure resistance is measured when the battery is in its static condition, that is, when neither the voltage rise nor the voltage drop resulting from the polarization and so on takes place in the electrolyte caused by charge or discharge.
As an example, there is a method for computing the pure resistance of a battery in which the battery is subjected to a repeated charge and discharge process by applying an alternating current with a frequency from 1 kHz to 100 kHz and in a condition that no polarization of charge or discharge is stored in the battery the pure resistance is computed from a relationship between voltage and current, which changes in a specific period of time, for example, 1 &mgr;sec.
That is, as shown in
FIG. 12
, after a charge is halted a phenomenon is investigated, in which the voltage recovers rapidly and thereafter gradually recovers. Supposing that said rapid recovery within a period of time &Dgr;t arises only as a result of the pure resistance R and said gradual recovery arises as a result of the other components (capacitance and inductance components) including the polarization excluding the pure resistance, a change in the voltage and current in a short period of time in each applied cycle of the alternating current with a frequency from 1 kHz to 100 kHz is investigated so as to measure the pure resistance.
However, when an on-vehicle battery is a subject for the above mentioned technique, the static condition of the battery exists in a very limited period of time and such a technique cannot be used when the vehicle is in operation.
Moreover, in the example described above, because the data of the voltage V and current I must be collected in a short period of time, that is, because the sampling during a short periodic period of time together with their analog/digital conversion must be carried out in a specific period of time &Dgr;t, therefore although it can indeed be used as an instrument which can be used independently, to use it while mounting it on the vehicle is very hard to do. Further, in order to make the computed &Dgr;V/&Dgr;I to be accurate each value of &Dgr;V and &Dgr;I inevitably must be large, however in the vehicle a case in which such a condition is established is very much limited. Consequently, the technique described above cannot be applied to a case in which the pure resistance of an on-vehicle battery must be measured when the vehicle is in operation.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to solve the above problem and to provide a method and device for measuring a pure resistance of an on-vehicle battery, by which the pure resistance of the battery can be measured even when the vehicle is in operation.
In order to attain the above objective, the present invention provides a method of measuring a pure resistance of an on-vehicle battery for supplying electric power to loads in the vehicle comprising the steps of:
periodically measuring a discharge current and terminal voltage of the battery while a rush current flows into a predetermined constant load of the loads, the rush current first monotonically increasing from zero to a peak value and subsequently monotonically decreasing from the peak value to a steady value;
computing a first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current, said current-voltage characteristic indicating a correlation between the discharge current and terminal voltage of the battery; and
computing an intermediate value of two values of the terminal voltage change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component when the first and second approximate expressions include the voltage drop, wherein the intermediate value computed is taken as a measurement of the pure resistance of the battery.
With the construction described above, the discharge current and terminal voltage of the battery are measured when an electric power is supplied to a load in a normal operation of a vehicle. The pure resistance of the battery can be computed only by processing the data thus measured.
That is, the present invention provides a method of measuring a pure resistance of an on-vehicle battery, by which the pure resistance of the battery can be measured even when the vehicle is in operation.
Preferably, the intermediate value is computed by averaging the two values of the terminal voltage change.
With the construction described above, the present invention provides a method of measuring a pure resistance of an on-vehicle battery, by which the pure resistance of the battery can be accurately measured when the change in the activation polarization at a point corresponding to the peak value becomes the same.
Preferably, each said value of the terminal voltage change is first multiplied by a cor
Armstrong Kratz Quintos Hanson & Brooks, LLP
Benson Walter
Yazaki -Corporation
LandOfFree
Method and device for measuring pure resistance of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for measuring pure resistance of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for measuring pure resistance of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3258911