Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-07-03
2001-03-06
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S134000, C320S136000, C429S061000, C324S427000, C324S433000
Reexamination Certificate
active
06198254
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery capacity measurement apparatus, and in particular, to a battery capacity measurement apparatus, taking a gassing voltage into consideration, wherein a full charge capacity during traveling is estimated from a gassing voltage that changes relative to temperature.
2. Description of the Related Art
Electric vehicles use a battery for traveling, hence it is important to accurately estimate the remaining capacity.
For example, in a battery remaining capacity apparatus disclosed in Japanese Patent Application Laid-Open (JP-A) No. 7-278351, a battery controller determines the remaining capacity SOC (also referred to as “dischargeable capacity”) of a battery immediately after turning on the ignition from a following expression (1), as shown in
FIG. 1
, in view of an easy calculation, and displays this:
SOC=[(Vn
2
−Ve
2
)]/(Vs
2
−Ve
2
)]×100% (1)
wherein
Vn: estimated voltage of a battery
Ve: discharge terminating voltage
Vs: full charge voltage.
The full charge voltage Vs is a voltage related to a new one in which a battery does not deteriorate, and is a voltage when the battery is charged at a temperature of 20° C. so as to be fully charged up to 100%.
Calculation of the aforesaid remaining capacity SOC is performed as described below.
The discharge current from the battery and the terminal voltage are collected in a predetermined number to be averaged on a voltage-current coordinate, and when the predetermined number of the averaged data are collected, a correlation coefficient r of the data is determined.
Next, when the correlation coefficient r shows a strong negative correlation, a regression line (also referred to as “approximation line”) of the data is determined from the method of least squares. From the approximation line Y (Y=a·X+b) and a reference current Io, the estimated voltage Vn of the battery at present is estimated.
Then, using the estimated voltage Vn, the present remaining capacity SOC during traveling is determined from the full charge voltage Vs corresponding to the remaining capacity 100% and the discharge terminating voltage Ve corresponding to the remaining capacity 0%, according to the above-described expression (1), and displayed.
Moreover, in hybrid vehicles comprising an engine and a motor, and driven by either of these, a battery controller has recently been used. During traveling, if the remaining capacity decreases, regenerative electric power from an alternator of the hybrid mechanism (a mechanism having a plurality of power sources comprising an alternator, an engine and the like) is charged to the battery. The remaining capacity during traveling is controlled to 60% to 80% so that the battery controller used in such a hybrid vehicle can charge the regenerative electric power at all times during traveling.
However, in general, batteries have such characteristics that the capacity decreases at low temperature compared to that of at the time of high temperature, and at the time of low temperature, even if the battery is fully charged, the capacity does not reach 100%, and for example, the capacity is 80%.
Moreover, there is a case where even if the battery is fully charged, the capacity does not show 100% due to deterioration of the battery, and the capacity shows, for example, 80%.
That is to say, if a temperature drops, or the battery is deteriorated, the remaining capacity does not show 100%, even if the battery is fully charged, hence overcharge occurs.
At the time of high temperature, on the contrary, the voltage of the battery tends to be high, causing insufficient charge.
That is to say, there is a problem in that it cannot be accurately judged, from the remaining capacity of the battery, how much it is chargeable during traveling.
In particular, with a method of determining the remaining capacity from the above-described expression (1), the remaining capacity actually shows 100%, only when the battery is fully charged at a reference temperature (20° C.), in a non-traveling condition.
Accordingly, to prevent an error from arising during traveling, because of the capacity change of the battery due to the temperature, there is a method in which the full charge capacity in the non-traveling condition is made 100%.
However, even if it is attempted to apply this method to a hybrid vehicle in which regenerative electric power of the alternator is charged to thereby keep the remaining capacity (dischargeable capacity) constant during traveling, the temperature changes even at the time of traveling. Therefore, if the method using the expression (1) is applied to the hybrid vehicle, the determined remaining capacity is not a reliable charge capacity, causing a problem in that overcharge or insufficient charge occurs.
On the other hand, batteries reach a gassing voltage (a voltage at which generation of gasses becomes active), when the charge capacity exceeds 90%.
With the conventional remaining capacity measurement apparatus of a battery, however, there is a problem in that calculation of the remaining capacity and charge are not performed, taking the effects of gassing into consideration.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the above-described problems, and it is an object of the present invention to obtain a battery capacity measurement apparatus, taking into consideration a gassing voltage that changes relative to temperature, which can accurately determine a full charge capacity during traveling, taking a gassing voltage and temperature into consideration.
To achieve the above-described object, there is provided a battery capacity measurement apparatus which charges a battery with power produced by the operation of a load in a constant current, when the remaining capacity of the battery decreases due to the operation of the load, to thereby keep a set full charge capacity during the load operation, and collects the voltages and currents of the battery to determine the remaining capacity of the battery from these voltages and currents, comprising: a temperature sensor for detecting the temperature in the vicinity of the battery; a gassing detection processing section which determines a gassing voltage of the battery, based on the temperature detected by the temperature sensor, every time the voltages and currents are collected, and detects that the battery is in a gassing condition, when the collected voltage is or exceeds the gassing voltage; a charge current changeover instruction processing section for instructing a changeover of the constant current value at the time of charging the battery to a smaller value, upon detection of the gassing condition; and a full charge capacity calculation processing section which reads the remaining capacity every time the gassing condition is detected, and determines the full charge capacity at the time when the load changes, from the remaining capacity at the time of gassing, a chargeable capacity set in advance, and a full charge capacity at the time of a reference temperature and no load, to thereby set the full charge capacity.
According to a preferred aspect of the present invention, the charge current changeover instruction processing section instructs a stepwise changeover of the constant current value at the time of charging the battery to a smaller value, every time the gassing condition is detected.
According to a preferred aspect of the present invention, the battery capacity measurement apparatus further comprises: a full charge voltage correction processing section which corrects the full charge voltage based on the ratio of the set full charge capacity to the full charge capacity at the time of a reference temperature and no load, every time the full charge capacity is set, and measures the remaining capacity based on the corrected full charge voltage.
According to a preferred aspect of the present invention, the full charge capacity calculation processing section determines the full charge capacity at
Enomoto Michito
Satake Syuji
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Toatley , Jr. Gregory J.
Wong Peter S.
Yazaki -Corporation
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