Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Patent
1995-04-06
1997-03-04
O'Shea, Sandra L.
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
320 48, G01N 27416, H02J 704
Patent
active
056083254
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of recalibrating a battery energy management processor.
2. Discussion of the Background
A self-contained vehicle with electric traction can be used only in an urban area on condition of knowing, as accurately as possible, the remaining endurance which its traction accumulator batteries can provide it with. The reining endurance of the vehicle corresponds to the distance or to the time for which the car can drive before exhausting the electric charge contained in these traction accumulator batteries. Knowledge of the remaining endurance of the vehicle is derived from knowledge of two factors. The first of these factors, Which is subjective, concerns the consumption of the vehicle over the journeys to come. This consumption depends in particular on the profile of the route, on the density of the traffic and on the mode of driving by the driver. The second factor, which is objective, concerns the charge which is recoverable at any instant from the traction battery.
The current devices indicating the recoverable charge, called gauges, are based on a measurement of the voltage at the terminals of the battery (Curtis-type devices, etc.). The accuracy of these devices is lower than 20% of the rated capacity for a new battery, and degrades considerably as a function of aging: the estimation error may exceed 50%.
Other devices are known, which here will be called "battery energy management processors", which measure the quantities of electricity alternately extracted and stored in the batteries managed by these processors, as well as the alteration in the maximum capacity of the batteries throughout their life. The evaluation of the quantities of energy actually stored in the batteries is only approximated, since the algorithm used is based on a weighted algebraic sum of the electrical current strengths measured in series with the managed batteries, and since the value of the maximum capacity of the batteries alters considerably as a function of the age and of the random aspects of use of the batteries. The errors made in each term of the algebraic sum (measurement errors, but also errors in the calculation of the energy actually stored by the charges, or available for discharges, and in the maximum capacity) cause the accuracy of the prediction of the available energy quantity to drift over time.
SUMMARY OF THE INVENTION
The subject of the present invention is a method making it possible to cancel out or greatly to reduce the drift in accuracy of the prediction of the quantity of electrical energy available in a battery, this method making it possible to maintain an accuracy which is markedly better than that of the known gauges, throughout the whole life of the battery.
The method of the invention consists, at the end of a defined period of time, in initiating a process of recalibration of evaluation of the quantity of electrical energy contained in the battery, in completely recharging the battery, in detecting the end of the complete recharge of the battery, in performing a partial discharge of the battery, in measuring the quantity of electricity extracted during this discharge, in leaving the battery to rest for a defined time, in totally discharging the battery at a low current while measuring the quantity of electricity thus extracted from the battery, in adding the said two quantities of electricity measured in order to obtain the value of the maximum capacity of the battery at the moment of the recalibration.
BRIEF DESCRIPTION OF THE DRAWING
The present invention will be better understood on reading the detailed description of an embodiment, taken by way of non-limiting example and illustrated by the attached drawing, in which the single figure is a diagram showing the alteration in the maximum capacity of an accumulator as a function of the number of charge and discharge cycles.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention is described below by reference to a traction accumulator ba
REFERENCES:
patent: 5352982 (1994-10-01), Nakazawa et al.
patent: 5539318 (1996-07-01), Sasaki
Chabbert Philippe
Chatenay Alain
Menard Christian
Meux Dominique
"Thomson-CSF"
O'Shea Sandra L.
Phillips Roger
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