SYSTEM FOR COLLECTING MEASUREMENT DATA IN BATTERY ROOMS

Abstract: A series of accumulator cells is monitored by means of special measurement processors (s), one measurement processor to each cell. Each measurement processor (s) comprises a number of sensors for measuring parameters like temperature, acid density, acid level and pole voltage, as well as a microprocessor. The microprocessor reads measurement values and supplies these values to a common data bus (d). Each measurement processor (s) takes its power feed current from the accumulator cell to which it belongs.

Description: SYSTEM FOR COLLECTING MEASUREMENT DATA IN BATTERY ROOMS The present invention relates to a method and a means for collecting measurement values from a number of sensors moni¬ toring physical parameters in respective ones of a series of accumulator cells. This may for example concern lead accumu¬ lators in a submarine, or emergency power batteries in power stations, hospitals or similar. It is common to all these uses that the accumulator cells are located as a collection in a battery of cells in a room which is classified as explosion dangerous. It is a known fact that lead accumulators liberate oxyhydrogen gas during charging. In explosion dangerous areas, strict regulations are enforced regarding safety and reliability of the electronic equipment to be placed there. In this connection there are several limiting parameters, like for instance the total energy which can be conducted into the explosion dangerous area. There are also a rather long series of general certi¬ fying provisions, with corresponding definitions and require¬ ments. In a battery room containing for example fifty accumula¬ tors in series, it is not difficult in theory to measure four physical parameters per cell and lead the signals out to a common data collection unit. However, this will require perhaps four times fifty conductor pairs, which will often be a very complex and space-demanding arrangement. In a submarine there may be a total of five hundred lead accumulator cells, and all of these may be connected in series. This means that there may be a DC voltage potential of almost 1400 volts between the lowest and the highest cell in the series connection. In a traditional sensor coupling, such a potential difference will create very large safety problems. The idea of the present invention is to solve in a prac¬ tical manner the problems arising in connection with both complex cable multitudes and the use of sufficiently low current to achieve a certificate in explosion dangerous areas class 1 or 0, and at the same time the problem in connection with high DC voltage potentials is solved. A means in accordance with the present invention also complies with all necessary requirements for approval in the explosion dangerous surroundings mentioned above. The objects just mentioned, are achieved by putting into use a method and a means of the kind appearing from the enclosed patent claims. A more detailed description of the invention will now be given, with reference to embodiment examples and the enclosed drawings, where fig. 1 shows a measurement processor, fig. 2 shows schematically a circuit connection containing several, possibly a few hundred measurement proces¬ sors, and fig. 3 shows optoisolators in one single measurement processor. In fig. 1 there is shown a complete measurement processor s. This processor is designed as a unit, which in its lower, elongated end part accomodates a number of sensors for measuring different physical parameters for an accumulator cell. In the top housing a microprocessor is located, which microprocessor reads measurement values from the respective sensors, provides current feed to the same sensors, and also delivers the measurement values, possibly in a somewhat pro¬ cessed form, via the connection cable c to a data bus d (see fig. 2) . The microprocessor is also adapted to receive requests via the same data bus. Reference numerals a and b indicate respectively positive and negative voltage feed wire connected to the poles of the accumulator cell where measurements shall be conducted by the measurement processor. Besides, also the cell voltage is measured by means of these two wires a, b. Other physical parameters to be measured are, typically, electrolyte density, electrolyte level and electrolyte tem¬ perature. Reference numeral c designates a two-pair cable connected to a common four-conductor data bus d. In fig. 2 the data bus d, measurement processors s and connection cables c from the measurement processors to the data bus are also present. These elements are located in the explosion dangerous area designated EX, and the data bus d leads out into a safe area S outside, where a so-called "zener barrier" e is placed in front of a collecting computer f which receives measurement data from the data bus d. This collecting computer f communicates with a control room via a data line g. A detail of the measurement processor microprocessor is shown in fig. 3, i.e. the detail consists of two optoisolators h and i, respectively an optoisolator for addressing the measurement processor s from the collecting computer f, and an optoisolator via which the measurement processor s re¬ transmits signals. As previously mentioned, the measurement processor s may contain several sensors for measuring cell voltage, tempera¬ ture, electrolyte level and electrolyte density for example. In addition, the measurement processor contains a micro¬ processor which collects and scales the measurement values from the different sensors. The microprocessor will also control the voltage feed to the different sensors, so that the voltage is disconnected in those periods where no measurements are conducted. The total power comsumption can then be reduced to a minimum when the sensors are "asleep". Only that part of the microprocessor which reads and recognizes its own address, possibly a common request, needs any power in this period. Each measurement processor has its own number, stored in e.g. an EEPROM in the microprocessor, and they can be addressed either one by one, or in larger groups. The measurement processor is preferably mounted solidly in the accumulator cell, and the feed voltage for the measure¬ ment processor is taken from the accumulator cell poles. This means that preferably the measurement processor can be manu¬ factured as part of the lead accumulator cell, and conse- quently it must be zone classified as a part thereof. Also regarding e.g. military certification procedures it will be favourable to define the measurement processor as part of the accumulator cell, or the measurement processor system as part of the accumulator cell battery. Lead accumulators are often built with two cells in a block. It is possible to provide a voltage from a series connection of two cells on the voltage feed wires. This may be favourable in certain cases, when it is desirable that the measurement processor shall function even when the cell vol¬ tage is substantially lower than the ordinarily acceptable minimum. When each measurement processor has its feed voltage from the cell in which a level is to be measured (or possibly a cell in series with a neigbouring cell) , the following is achieved: The sensor which reads electrolyte level can be of a capacitive type, using the electrolyte as one condenser side of the sensor. Thereby is eliminated the possible influence on the measurement from the varying electrical characteristics of the liquid, cp. British patent no. 1.318.512. The connection cable c is connected to respectively transmitter and receiver in two different optoisolators included in the microprocessor of the measuring processor. These optoisolators secure the necessary galvanic separation between the data line and the remaining part of the measure¬ ment processor. (The measurement processor may be situated at a potential of more than 1000 volts, while the data line has earth potential via the data collecting unit f.) The multiplexing of the measurement processors can be implemented in many well known manners, and this constitutes no part of the present invention.

Claims: P A T E N T C L A I M S 1. A method for simultaneously monitoring the condition of a number of accumulator cells which are possibly grouped in accumulator blocks containing at least two cells per block, where a microprocessor incorporated in a special measurement processor arranged in correspondence with each accumulator cell, reads measurement values from a set of sensors which are also incorporated in the same measurement processor and adapted to measure respective physical parameters of the cell, each measurement processor delivering the acquired measurement information via a connection cable to a common data bus which is connected to a collecting computer, c h a r a c t e r i z e d in that the necessary power feed for the microprocessor and sensors in the measurement processor is taken from the poles of the same accumulator cell or from the poles of the accumulator block comprising said cell. 2. A method as claimed in claim 1, c h a r a c t e r i z e d i n that the microprocessor in each measurement processor by it'self reduces the power con¬ sumption of the measurement processor by disconnecting all unnecessary microprocessor parts as well as the sensors in those periods where measurements are not conducted. 3. A means for simultaneously monitoring the condition of a number of accumulator cells which are possibly grouped in accumulator blocks containing at least two cells per block, each accumulator cell having a corresponding special measurement processor (s) which comprises a set of sensors adapted for measuring respective physical parameters of the cell and a microprocessor adapted to read and possibly process measurement values from the sensors, each measurement processor (s) being connected via a connection cable (c) to a common data bus (d) which is also connected to a collecting computer (f) , c h a r a c t e r i z e d in that each measurement processor (s) is connected to the poles of its corresponding accumulator cell or of the accumulator block comprising said cell, for feeding current to the microprocessor and the sensors of said measurement processor (ε) . 4. A means as claimed in claim 3, c h a r a c t e r i z e d i n that each measurement proces¬ sor (s) constitutes an integral unit adapted to be fixed or screwed in place in an accumulator cell. 5. A means as claimed in claim 3, c h a r a c t e r i z e d i n that each measurement proces¬ sor (s) is incorporated as an integrated part of an accumu¬ lator cell. 6. A means as claimed in any one of claims 3-5, c h a r a c r i z e d i n that the set of sensors in each measurement processor (s) comprises sensors for measuring the accumulator liquid temperature, level, density as well as the pole voltage of the accumulator cells. 7. A means as claimed in claim 6, c h a r a c t e r i z e d i n that the sensor for measuring liquid level is a capacitive level meter in which the electro¬ lyte (the liquid) constitutes one condenser side of the capa¬ citive sensor. 8. A means as claimed in any one of claims 3-7, c h a r a c t e r i z e d i that the microprocessor in each measurement processor (s) is adapted to reduce the power consumption of the measurement processor (s) by disconnecting all unnecessary microprocessor parts as well as the sensors in those periods where measurements are not conducted. 9. The use of a means as claimed in any one of claims 3-8, as a monitoring means for an accumulator battery in a sub- marine . 10. The use of a means as claimed in any one of claims 3-8, as a monitoring means for an emergency power unit which com¬ prises a number of accumulator cells.

Inventors: GOTAAS EINAR, GOTAAS, EINAR
Applicants: SKAND INSTR AS, SKAND-INSTRUMENT A/S
Application year: 1992
Main classification: H01M10
IPC codes: G01R31, H01M10