Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Patent
1995-04-06
1996-12-24
Arana, Louis M.
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
324431, G01N 2742
Patent
active
055876609
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for evaluating the remaining charge in an accumulator battery.
A self-contained electric traction vehicle cannot be used in an urban area unless the remaining endurance which its traction accumulator batteries can confer upon it is known as accurately as possible. The remaining endurance of the vehicle corresponds to the distance or time for which the car can run before exhausting the electric charge contained in these traction accumulator batteries. A knowledge of the remaining self-containment of the vehicle relies on a knowledge of two factors. The first of these factors, which is subjective, concerns the consumption of the vehicle over the trips ahead. This consumption depends in particular on the profile of the journey, on the density of traffic and on the driver's way of driving. The second factor, which is objective, concerns the charge restorable at each instant by the traction battery.
The existing devices which indicate the restorable charge, and which are called gauges, are based on measurement of the voltage across the terminals of the battery (Curtis type devices, etc.). The accuracy of these devices is less than 20% of the nominal capacity for a new battery, and deteriorates considerably on aging: the error of estimation can exceed 50%.
The subject of the present invention is a process for evaluating the remaining charge in an accumulator battery, which makes it possible to evaluate the remaining charge with the best possible accuracy, regardless of the conditions of use of the battery and regardless of its age.
The process according to the invention, for evaluating the remaining charge in an accumulator battery, according to which the residual charge at the start of discharge is determined and the quantities of electricity extracted as and when the battery is used are added up, is characterized in that account is taken of the quantities of charge which are not restorable instantaneously under the influence of the discharge rate and of the charge which is restorable by reducing the intensity of the current drawn from the battery.
The present invention will be better understood on reading the detailed description of an embodiment taken as non-limiting example and illustrated by the appended drawing in which:
FIG. 1 is a graph of the restorable charge of a battery, as a function of temperature, and
FIG. 2 is a graph of the restoring of the charge which is not restorable instantaneously of a battery as a function of time;
FIG. 3 is a graph of the changes in a coefficient involved in the formula giving the portion of the charge of a battery which is not restorable under the influence of the discharge rate, as a function of discharge current;
FIGS. 4 to 8 are examples of curves used by the process of the invention.
The invention is described below with reference to a traction accumulator battery for electric vehicle, but obviously it is not limited to such a type of accumulator and may be implemented for various types of accumulator, from the simple accumulator for small portable apparatus up to a large back-up accumulator set for stationary plant of high power. These accumulators can be of various technologies: lead, cadmium-nickel, etc. For simplicity, in the remainder of the text, the term battery will be used to designate any one of these accumulators or sets of accumulators.
The operating modes envisaged for the battery are as follows: discharge, charging when stationary, charge recovery by braking (valid only for the application to vehicles with energy recovery from braking or deceleration), and self-discharge during storage without use. To each of these modes of operation of the battery there corresponds a determination of the charge restorable by the battery, described below.
Mode of operation in the discharge regime:
Calculation of the charge remaining in a battery during the discharge phase amounts to calculating, for a set of consecutive time spans .DELTA.t, the value Ch.sub.(t) whose mathematical expression (1)is given a little later on.
In th
REFERENCES:
patent: 4377787 (1983-03-01), Kikuoka et al.
patent: 4952862 (1990-08-01), Biagetti et al.
patent: 5130659 (1992-07-01), Sloan
patent: 5349540 (1994-09-01), Birkle et al.
Chabbert Philippe
Chatenay Alain
Meux Dominique
"Thomson-CSF"
Arana Louis M.
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