GB2219151A - Battery charging - Google Patents

Description

2219 151 AP.Paratus for charszing accumulators 1

The invention relates to an apparatus for the charging of accumulators, in particular nickel cadmium accumulators (NC), which comprise a device for the identification of the accumulator type and possibly for sensing its temperature, according to the features set out in the preamble to Patent Claim 1.

Accumulators, particularly strong current-resistant nickel cadmium accumulators (NC batteries), are very expensive supplies of power to appliances which have to operated independently of the mains and which can only be used to a certain extent economically if the effective life of the batteries used is relatively long.

The effective particularly however of at the outset, depends profile, from its initial operation to the present time. This usage profile represents the time-related pattern of operating parameters in terms of charging current, discharge current, cell voltagre, cell temperature and cell pressure.

life of any accumulator, but an accumulator of the type mentioned quite considerably upon its usage its While the operational discharge of an accumulator in a battery-operated appliance is largely determined by the use of the appliance, there are various ways of recharging the accumulator, ranging from a fast charge, a semi-fast charge and a slow charge right down to trickle charge. Chargers which can be switched to these various charging rates are currently already in use. The criteria which are individually applied for a switch- over between the types of charge are based on generally physical considerations which emerge substantially from the diagram in Fig. 5 which indicates the characteristic conditions of an individually defined NC cell. The graphs shown are cell-individual.

both type-specific as well as being The acceptable band width of the p % 2 - cell-individual graphs can thus be represented for each type of cell by a series of graphs provided by the upper and lower as yet still tolerable values.

For the effective life of an accumulator, special problems arise if this is operated at too high a discharging and/or charging current, is overcharged or is discharged as far as a point where it falls short of a specific acceptable minimal cell voltage. Problems also occur with rapid charging which the user employs in order to have his appliances ready for use again as quickly as possible or in order to minimise the number of batteries used, on grounds of cost, or in order to maintain operation as far as possible without interruption. On theone hand, with rapid charging, one also wishes to be sure that after a complete charging operation the cell(s) is/are actually full. On the other hand, the accumulator can also tolerate a certain amount of overcharge.

If it is overcharged, then the pressure in it rises very quickly due to the development of gas and so intensely that the built-in safety valve responds and the cell possibly runs out. The opening of the safety valve does in fact avoid damage which would lead to destruction of the cell but there is however a reduction in capacitance.

An often-practised and reliable method of charging a battery is that of first discharging it completely and of then charging it for -a specific time at a specific current. In this way it is possible to avoid overcharging a still half-charged accumulator which would have the results mentioned above. Fig. 5 shows that the voltage rises very quickly and the pressure and the temperature only slowly as the charge increases. Thus, in the cell, an increasing proportion of the supplied energy is converted to gas (oxygen) which cannot be chemically bonded in the electrodes in the time available. Therefore, the pressure rises accordingly and ensures that some of the oxygen released becomes bound to the negative electrode with a development of heat. With rising temperature, the voltage drops again. Therefore, NC cells have a negative temperature coefficient of about -4mV/OC.

- 3 c This explains the pattern of the voltage characteristics of the cell with the initially rising voltage which after attainment of a complete charge (100%) does indeed continue to increase somewhat only to drop again as the overcharge increases. The major part of the energy supplied is, as Fig. 5 likewise shows, converted to heat. The parameters illustrated are a measure of the charging condition of a cell and represent reliable information for a charger which continues, monitors and completes the charging process Chargers for NC accumulators with a slow-fast and semi-fast charge are already adequately known. For example, DE-OS 26 51 067 describes a rapid charging apparatus in which an accumulator which is to be charged is first charged with an increased charging current up to a predetermined percentage of the final charging voltage which is to be attained whereupon this first rapid charging phase is followed by a further charging phase at a reduced charging current for a predetermined period. In order reliably to avoid a harmful overcharging, it is in addition suggested that the second charging phase possibly be prematurely discontinued when a predetermined terminal voltage or a predetermined temperature of the accumulator is reached or exceeded.

In this respect, this charging apparatus, just like other known rapid charging apparatuses are based on the assumption that recharging is achieved after a predetermined time or at a clearly specified terminal voltage and that after switching off, each individual accumulator is charged to approximately the full rated capacitance. However, this is often not the case because all manner of influences in course of time (working time, overcharges, short circuits and the like) will to an increasing extent diminish the energy which can be stored in such a battery. This reduction in charging is thereby generally established only when the appliance which is to be operated on the battery suddenly fails during the period of its readiness for use which is intolerable particularly in the case of emergency equipment, but also communications equipment used in the event of a capacitance - 4 catastrophe. This lack of knowledge of the actual prehistory of an accumulator prior to its renewed charge always leads to more unfavourable conditions for the accumulator so that it is charged loss of capacitance unusable.

in a way which always leads more rapidly to a further until the accumulator or battery becomes Therefore, the present invention is based on the problem of indicating a solution by which accumulators, particularly those which are not permanently associated with an appliance can be charged in such a way as to permit of a long working life of the accumulator in terms of high current strength and high capacitance levels.

This problem on which the invention is based is resolved by the features indicated in the main claim.

Further advantageous developments of the object of the invention can be ascertained from the sub-claims.

The way indicated by the invention as to how it is possible to achieve an accumulator-specific charge in fully-automatic chareers results in the advantage of a tz prolonged accumulator life while maintaining the greatest possible capacitance and cur.rent strength.

0 The invention will reference to an example of embodiment which is illustrated in the accompanying drawings in which:

be described hereinafter with Fig. 1 is a diagrammatic view of an NC accumulator with a built-in type identification means and an incorporated temperature sensor, Fig. 2 is a circuit diagram of an arrangement for generating and storing a usage and/or operating parameter profile and for generating control signals for a charger, Fig. 3 is a circuit diagram of an accumulator charger, 1. 1 Fig. 4 is a circuit diagram of a charging circuit, Fig. 5 is a graph showing operating parameters of an NC cell, 0 Ficr. 6 shows in principle a current measuring device, 0 Fig. 7 shows in principle a charger having a series-parallel convertor for supplying setting signals and Figs. 8 to 10 show in circuits.

principle chargers which have thyristor On account of the normally conventional separation of accumulator consumer unit and charger, whereby by the use of a plurality of accumulators, consumer units and chargers, a clear relationship is no longer evident, there is provided in the accumulator a device which records the time-related patterns of charging and discharging currents, voltage, temperature and pressure. Such a device can be accommodated in the power pack, in other words in the case of a necessary grouping together of a plurality of NC cells to form a power pack, using the technology of microelectronics. Previous power packs, as Fig. 1 shows, contain not only the NC cells (2) but al;o identifying means (3), resistors, diodes or the like, for identifying the type of accumulator as well as possibly temperature sensors (4) which can be connected to a charger via the external connections (5 to 8).

An apparatus which can both store and also store in its memory the timerelated pattern of the above-mentioned parameters is shown in principle in Fig. 2. It may consist of a fixed or a flexible circuit board (21) accommodating one to a plurality of semiconductor chips (9 to 17), the necessary wiring and also the connections to the outside world.

Within the scope of a desired low - loss of power within the range of a few pickets, it is necessary for constructing, 0 1 - 6 the circuits in the microchips to use the prior art CMOS technology which is available in various alternative forms. The main element of the apparatus (21) is a microprocessor (MP; 9) which already has a reading memory (ROM) in which there is for example a control programme. The additional electrically erasable and programmable reading memory (EEPROM; 10) serves to receive the measured data which are processed and stored to provide the parameter patterns. In addition, it contains tables, the accumulator type specific graphs of the -parameters and thus the admissible band width of these parameters.

Furthermore, a clock generator (TG; 16) is provided which synchronises the cycles in the apparatus (21) and which serves as a time base for recording the time-related pattern of the parameters. Traffic with the outside world takes place via an interface (SCHN; 17) via which analogue input signals, the voltages, voltage-dependent resistances, temperature and pressure-dependent resistances as well as type identifying signals in the form of resistances or diode voltages are supplied and are transmitted via the digital output signals (ES) for the adjustment of any particularly desired charging current to a charein-r circuit (29).

0 0 The said analogue input si-gnals for accumulator voltage (UAK), type identification (ID) and temperature sensor (TF) must first be converted to a digital form of representation in an analogue/digital converter (A/D; 11), so that they can be processed digitally in a microprocessor (8) and the other components, a comparator (VGL; 12), a temperature monitor (TU; 13), a type recognition device (TE 14) and a current measurinr 15) is.possible.

circuit (STM; If the number of conductors, for example those which are connected to the connection point (22 to 26) and which transmit the setting signals (ES) to the charger (27) in Fig. 3 are as far as possible confined to one conductor, then in the device (21), at the appropriate outputs from the interfaces (177), it is necessary to connect a series/parallel t - ' 1 7 converter which in the simplest case may be a 5-position shift register. In operation, its five stages will be charged in parallel and then via an output, be transmitted serially to the charging circuit (LS; 29) in the charger (27).-This latter 2 0 0 then, in contrast to the view in Fig. 3, precedes a series/parallel converter which may likewise consist of a 5-position shift register the five stages of which can be chargid serially and scanned in parallel. The parallel outputs are thereby connected to the inputs of the charging circuit (29). These converters are not shown in either Fig. 2 or in Fig. 3 (see however Fig. 7).

For the derivation of the pressure parameters, there is provided in the power pack (1) a pressure sensor which, according to its basic physical principle, generates a voltage ar a resistance corresponding to the particular pressure in question. Such an analogue value is then likewise supplied via the interface (17) and is fed via an analogue/digital converter (11) to a digital further processing means.

to ascertain the currents (charging and it is advantageous to use a Hall In order discharging currents), generator (HG; 37) which measures the magnetic field of an extremely low-ohm coil (36) which is incorporated into the main current path. There is created thereby a Hall voltage which is dependent upon a material constant, a transverse current and the strength of the magnetic field of the coil in the main current path. Since the strength of the magnetic field is in turn dependent upon the current in the main current path, the charging or discharging current which flows through the main current path and thus through the coil can be used for measuring the current. The current measuring device (15) can in this case calculate the charging or discharging current in conjunction with the measuring circuit (35) which is connected by the interface. At this point, it should be mentioned that the functions of the circuits at the chips (11 to 15) can also be shifted to a microprocessor (9) of corresponding intelligence.

it Also of great use may be a display means (ANZ; 60) which makes it possible to indicate accumulator data which may be of interest in respect of the state of charge of the associated battery at -any given moment, data which may be stored or which may be in process of being scanned.

Here, one or multi-point numerical or alphanumerical liquid crystal displays are recommended which, as is well known, have only a low loss power.

In principle, it is immaterial whether the display means is disposed on the circuit card itself or is separate therefrom, in the power pack itself. The only feature which speaks against a separate arrangement is the additional connection (61, 62) source of disturbance.

which represents a possible subsequent The time-related pattern of currents (charging and discharging currents) can thus likewise be stored in the memory (10). For carrying out the data processing and controlling functions, a data bus (DB; 20), a clock bus (TB; 19) and a control signal bus (STB; 18) are available which combine the individual system components with one another.

The charger (27) shown in Fig. 3 requires no tremendous intelligence of its own for careful charg ging of an accumulator, since this is in the main provided for in the apparatus (21) which is installed in every power pack. Thus, it only consists of two components, namely the power supply (SP; 28) which generates from the mains voltage or the voltage of a suitable battery or of another suitable accumulator a direct current voltage of the desired level.

p This direct current voltage is applied to the power pack via a charging circuit (29). In a manner not shown in Figs. 3 and 4, the type-specific setting signals which are applied to the charging circuit (29) via the contacts (24 to 26) are also used in the power,supply circuit (28) to generate various levels of direct current voltages which are fed to the -9 Z il 1 charging circuit (29) via (33 and 34). Some of the output signals (T1 to T8) from the decoder (31) can be transmitted to th: power supply circuit (28) in order there to generate these variously high direct current voltages which are required for z charging power packs of different rated voltages.

Fig. 4 shows one of a plurality of possible alternative ways of generating the charging currents for four types of charge and eight different types of power packs. The setting signals (ES) which are applied to the charging circuit (29) via the connections (22 to 26) reach a first binary decoder (DEC1 30) and a second binary decoder (DEC2; 31). While the first decoder (30) generates from the first two control signals which are supplied via the first two connections (22 and 23) the charging type signals for fast charge (SL), semi-fast charge (QL), for slow charge (LL) and for trickle charge (EL), are decoded to produce type signals (T1 to T8) from the following setting signals to the connections (24 to 26).

A third decoder (DEC3; 32) on the downstream side generates 32 setting signals each of which is representative of a type of charge of a type of power pack. Fig. 4 shows a decoder (32) which decodes the twelve input signals (SL to EL and Tl tp T8) from 32 according to principle 1. The resultant output signal from this decoder (32), for example (SL/T1 or EL/T1 or EL/T8) can be regarded as a control signal for a controllable switch (S1 to S32) which loops in a current limiting resistor (Rl to R32) into the main charging current circuit. Such a main current circuit extends for example via the +conductor at the connection point (33), a closed switch (Si), a current limiting resistor (Ri), the connection point (5), the positive pole of a power pack (2) (Fig. 1) and the connection point (6) to earth.

With a favourable layout, two or more current limiting resistors can be connected in parallel so that the component expenditure can thus be reduced. The decoder (32) must then have a different kind of internal setup which makes - 10 it possible for it to use other decoding principles which will on the one hand cope with the multiplicity of charm-,in=c currents and on the other the reduced expenditure of components in terms of power limiting resistors (Ri) and selections which is (Si).

A different embodiment of charger which can be controlled by a device (21) individually associated with a power pack is shown in Fig. 7. The charger (43) shown therein in turn consists of a power supply (45) and a charging circuit (46), this latter feeding the setting signals serially via the connection (22). The setting signals pass via a shift register (SR 44) which is connected as a series/parallel converter to the charging circuit (46). The setting signals which are transmitted bit-wise and which serially arrive at the input (E) of the shift register (44) are applied by means of five shift pulses which are applied to the clock input of the shift register and are fed into the five stages. At the outputs from the five stages of the shift register, it is now possible to tap the five setting signals in parallel in fact until such time as fresh setting signals are transmitted by the device (21) to the charger (43) so that a different charging current and/or a different charging voltage are adjusted.

The principle assumption that the controllable rectifiers with a thyratron characteristic. The charging circuit (46) then contains the control elements, also referred to as starting elements, which set the desired power flux angle. The setting signals (ES) then serve either in the manner explained already in conjunction with Fig. 4, by means of the controllable switches (S1 to S32), to apply'startincr members (ZGLi; 53, 54, 55) having definite starting moments (determined by (RC members) contained in them to the control electrode (SE) of a thyratron (52) for adjusting the desired power flow angle or, as Fig. 8 shows, in a charger (.47) of a different type (e.g. in a bridge circuit (BS) in a power supply (48) to control the thyristors (52) via a control line illustrated in Fig. 7 also explains the power supply circuit (45) uses T 11- 1 (51) by means of a starting member (50) in which the setting signals (ES) conveyed by the device (21) and the connection point (22) have already been generated as trigger pulses in respect of the type of charge and of the power pack of calculated duration. As Fig. 8 shows, this leads to a particularly economical embodiment of charger (47).

12 -

Claims (1)

1. CLAIMS:

   An apparatus for charging, accumulators comprising means of identifying the battery type and possibly for sensing its temperature, with a power supply means and with a charging circuit comprising a switch-over means so that the charging can be fast, semi-fast, slow or trickle charge and serve for one to several types of accumulator, characterised in that to adjust the type of charge and thus the charging currents of the charging circuit, setting signals are fed thereto having been ascertained by comparison of the individual charging current, discharging current, voltage temperature and/or pressure-time profile formed and stored in a device permanently associated with the relevant accumulator with a likewise stored desired profile.

   2. An apparatus for charging accumulators according to Claim 1, characterised in that the device which is permanently as'sociated with an accumulator or a power pack comprises a data processing arrangement comprising at least one microprocessor, a memory, an analogue/digital convertor, - a comparator, clock generator. a temperature monitor', battery type recognition circuit, device and an interface circuit connected to one another by means of a data bus, control signal bus and a clock bus.

   a a current measuring which are An arrangement according to Claim 1 and/or2, characterised in that the components of the device which is permanently associated with the W J h 1 p 7 accumulator are disposed on a circuit board comprising the necessary connecting conductors.

   4. An arrangement according to one or more of the preceding Claims, characterised in that the memory of the data processing arrangement is an electrically erasable and programmable reading memory of the EEPROM type which does not lose its content upon current failure.

   5. An arrangement according to one or more of the preceding Claims, characterised in that the memory is a dynamic or static reading/writing memory (RAM) with which there is associated an EEPROM memory which, when the accumulator voltage falls below a predetermined minimum value, operation to continue takes over the data urgently required for 6. An arrangement preceding Claims, main current path according to one or more of the characterised in that there is in the a cutout switch which opens the main current path when a predeterminable minimum voltage is reached at the accumulator during discharge, in order to avoid excessive discharge and possibly reversal of the accumulator cell polarity.

   An arrangement according to one or more of the preceding Claims, characterised in that the functions of the analogue/digital convertor, of the comparator of the temperature monitor accumulator type recognition means into the microprocessor.

   and of the are integrated An arrangement according to one or more of the--preceding Claims, characterised in that at least the desired profiles mentioned in Claim 1 are stored in tabular form.

   An arrangement according to one or more of the preceding Claims, characterised in that the setting signals calculated from comparison of the actual values with the desired values of the said profiles by the microprocessor and which are transmitted serially or in parallel to the charging circuit of a charger are passed to at least one decoder generates charging signals case adiust a which type and accumulator specific control which in turn in each controllable switch which in each case loops into the main current path a power limiting resistance corresponding to a desired type of charge and type of accumulator.

   An arrangement according to Claim 9, characterised in that the decoder(s) also generate two or a plurality of parallel control signals, so that simultaneously two or a plurality of controllable switches are adjusted and two or a plurality of current limiting resistors are looped into the main current path in parallel.

   An arrangement according to Claim 9 or 10, characteri.sed in that a part of the control signals derived from the setting signals decoding is^ transmitted to the power supply means., where at least one controllable switch sets a different starting voltage.

   by 12.

   An arrangement according to one or more of Claims 1 to 9, characterised in that the setting signals, after being decoded, are adjusted to control signals by means of the same controllable switches which apply starting members for setting individual current flow angles which correspond to a desired type of charging operation for a desired type of accumulator, to the control electrodes of a controllable rectifier with a thyristor characteristic.

   v A 4 k - is - 13. An arrangement according to one or more of the preceding Claims, characterised in that a display device is provided which is connected to the device and which indicates stored a6d/or derived situation values of accumulator parameters (charge, voltage or the like).

   14. An arrangement according to Claim 13, characterised in that a singleor multi-position numerical or alphanumerical liquid crystal display is provided as the display device.

   15. An arrangement according to Claim characterised in that the display device on the circuit board.

   16. An arrangement according to Claim characterised in that the display device from the circuit board, in the power pack.

   1 13 or 14, is disposed 13 or 14, is separate P.hiiah@d ioag atThe patent 0Moe. SmteHmise,66171 High nolbomljondonWC1R4TP.Purthercopies be obtatiodfrom The Patent.