Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Patent
1999-05-19
2000-11-14
Wong, Peter S.
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
320119, H02J 700, G01N 27416
Patent
active
061474991
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a battery voltage measurement device and in particular to a battery voltage measurement device that is ideally suited to voltage measurement of each of the secondary batteries in a power source device wherein a large number of secondary batteries are connected in series.
BACKGROUND ART
In power source devices in for example electric vehicles, an arrangement is adopted whereby a large number of secondary batteries are connected in series to obtain a prescribed drive voltage. In order to ensure reliability and stability of such power source devices, it is necessary to constantly monitor the respective conditions of each of the secondary batteries. For this purpose, it is known to provide a battery voltage measurement device for measuring the voltage at both terminals of each secondary battery.
In such a prior art battery voltage measurement device of this type, as shown in FIG. 4, to each secondary battery 11 there are connected a differential amplifier 12 for obtaining output voltage corresponding to its two terminal voltages and a gain trimmming amplifier 13 for performing gain trimmming of this output voltage. Further, as shown in FIG. 5, the output voltage from each gain trimming amplifier 13 is converted into a digital value by an A/D converter 14 respectively provided corresponding thereto and the digital signal corresponding to the voltage of the two terminals of each secondary battery 11 is input to a microcomputer 15, and the voltage of each secondary battery 11 is thereby detected. As shown in FIG. 4, all the differential amplifiers 12 have their power source terminals and ground terminals respectively connected in common, and power source voltage Vcc is applied by connecting a common control power source between their power source terminals and ground terminals, and their ground terminals are connected to a common ground GND.
The reason for performing respective gain trimmming by connecting gain trimmming amplifiers 13 to each differential amplifier 12 is as follows. In order to achieve digital conversion of the output voltages of the differential amplifiers 12 so that these can be sent to microcomputer 15, the gains of differential amplifiers 12 must be matched with the voltage range of the A/D converter 14 in which input is possible. For example, if the detection range of the battery voltage is 0 to 20V and the input voltage range of A/D converter 14 is 0 to 5V, the battery voltage at differential amplifier 12 must be output multiplied by a factor of 1/4.
However, the differential amplifiers 12 have an in-phase input range consisting of the voltage range in which they can operate normally by application of voltage to their input terminals and are subject to restriction in regard to their input voltage range, depending on the device characteristics and power source voltage. For example, when a certain device is used as a differential amplifier 12, its in-phase input range, when the power source voltage VCC is +15V, is 14V. This in-phase input range differs somewhat depending on the device used to constitute differential amplifier 12 but in general is a value a little lower than the +15V of the power source voltage Vcc, so its value may be taken as 14V. On the other hand, since a large number of secondary batteries 11 are connected in series, as shown in FIG. 6, it may happen that the voltage Va of one terminal of a given secondary battery 11 is for example 200V with respect to ground; in such a case, too, it is necessary to ensure that the input voltage Vb does not exceed 14V, which is the in-phase input range. Consequently, in regard to R.sub.1 and R.sub.2 of FIG. 6, R.sub.2 /R.sub.1 must be made .ltoreq.14(200-14) and in this case the gain of the differential amplifier 12 has to be below R.sub.2 /R.sub.1 (=7/93). Accordingly, in order to match the input range of the above A/D converter, a gain trimmming amplifier 13 of gain R.sub.1/ 4R.sub.2 (=93/28) is required.
However, there was the problem that in the above construction costs were greatly
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Nakanishi Toshiaki
Torii Yuji
Matsushita Electric - Industrial Co., Ltd.
Toatley Gregory J.
Wong Peter S.
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