METHOD FOR THE CYCLICAL TRICKLE CHARGING OF A CHARGEABLE BATTERY INTENDED FOR EMERGENCY OPERATION

Abstract: The charging voltage used for this purpose is the output voltage from a source of d.c. voltage providing a variable level of output voltage. A characteristic feature of the invention is the fact that charging from a starting mode (1) is executed in accordance with a cyclical charging programme (10) which is repeated until the battery has been found to be fully charged. A rest mode (13) then occurs during which the battery is not charged, but the battery voltage is measured continuously. The rest mode (13) is interrupted immediately, and the aforementioned charging programme (10) is re-started if it is noted in the course of measuring the votalge that the battery voltage has dropped below a first predetermined value. Once the rest mode (13) has lasted for a predetermined period, a discharging phase (17) will be initiated which involves the battery being discharged in accordance with a discharging programme during which the battery voltage is measured continuously. The discharging phase (17) is interrupted if it is noted in the course of measuring the voltage that the battery voltage has dropped below a second predetermined value. Once the discharging phase (17) has been interrupted or completed, the charging programme (10) is restarted.

Description: Method for the cyclical trickle charging of a chargeable battery intended for emergency operation. The present invention relates to a method for the cyclical trickle charging of a chargeable battery intended for emergency operation, in which case the charging voltage used is the output voltage from a source of d.c. voltage providing a variable level of output voltage, said source of voltage being connected to the battery via a charging regulator. Batteries of this kind are usually part of a group of batteries in which the number of batteries is determined by the number of Ampere—hours which need to be available when the regular mains electricity supply fails. When this occurs it is important for the battery to function in the intended manner. A further requirement is that the battery is fully charged and exhibits the specified battery voltage. If this is not the case the battery may suffer damage, or at -any rate be impaired, within such a relatively short interval of time as one year. The battery is trickle charged in order to keep it at a high level of readiness for emergency operation, and this takes place in a conventional manner by connecting a continuous charging voltage across the battery, by means of which the battery voltage is made to stay at the specified value. The battery will suffer damage in spite of such trickle charging, mainly for the reason that it is unable to operate in the manner for which it was constructed and dimensioned. The object of the present invention is to make available a method of charging of the kind referred to by way of introduction which does not suffer from the aforementioned disadvantages. The way in which this is achieved is for charging to be executed from a starting mode in accordance with a cyclical charging programme which is repeated until the battery has been found to be fully charged, whereupon a rest mode will occur during which the battery is not charged, but the battery voltage is measured continuously, whereupon the rest mode is interrupted immediately and the aforementioned charging programme is re—started if it is noted in the course of measuring the voltage that the battery voltage has dropped below a first pre—determined value, whereupon, if the rest mode has lasted for a pre—determined interval of time, a discharging phase will be initiated which involves the battery being discharged in accordance with a discharging programme during which the battery voltage is measured continuously, whereupon the discharging phase will be interrupted if it is noted in the course of measuring the voltage that the battery voltage has dropped below a second pre—determined value, whereupon, once the discharging phase has been interrupted or completed, the charging programme will be re—started. According to another characteristic feature of the invention charging is executed in such a way that charging from a starting mode is executed at a normal charging voltage for an interval of time (a) consisting of a single number of minutes, whereupon an assessment is made whether a considerably longer interval of time b in relation to the interval of time a, preferably a single number of days, has elapsed since the starting mode, whereupon, if this is not the case, a check is made during a measurement phase whilst the battery is subjected to load of whether the battery voltage drops below a certain value within a certain interval of time c of the same order of magnitude as, but shorter than the interval of time a, whereupon, if this is the case, charging takes place at an increased voltage for an interval of time d of the same order of magnitude as, but longer than the interval of time a, followed by charging at a normal charging voltage for an interval of time er of the same order of gnitude as, but shorter than the interval of time a, whereupon the aforementioned assessment is made once more, whereupon, if the battery voltage does not drop below the aforementioned value within the aforementioned interval of time e, charging takes place at a normal charging voltage for an interval of time f consisting of a single number of hours, whereupon the charging cycle reverts to the point after the starting mode, whereupon, if the considerably longer interval of time b in relation to the interval of time a has elapsed since the starting mode the battery will be subjected to load for a certain interval of time or until the battery voltage has dropped to a pre—determined value, depending on the capacity of the battery, whereupon the charging cycle will revert to charging at the increased charging voltage during the aforementioned interval of time. The invention is explained in greater detail below with reference to the accompanying drawing, in which Fig. 1 is a flow chart which illustrates the method according to the invention for the cyclical trickle charging of a battery. Fig. 2 is a flow chart which shows an alternative method according to the invention for the trickle charging of a battery. The reference designation 1 is used in Fig. 1 to indicate a starting mode during which certain routine control measurements, amongst other things, are performed, as indicated by a block 2. The starting mode 1 is followed by a charging programme which involves charging at a number of different voltages for. different intervals of time, plus measurements, for instance in accordance with a programme which is identical or similar to that which will be described in relation to Fig. 2. The charging programme is represented in Fig. 1 by a block 10. The block identified by the figure 11 indicates an option stage at which an assessment is made of whether the battery has been fully charged during the charging programme. If this is not the case the charging programme 10 is repeated, as indicated by the arrow 12. If the battery has been fully charged a rest mode 13 will occur, during which the battery will not be charged. The battery voltage is monitored continuosuly during the rest mode, and this will be interrupted immediately and replaced by the charging programme 10, indicated by an arrow 15 connected to the arrow 12, if it is found in assessment block 14 that the battery voltage has dropped below a pre—determined value, for example by 1.3% of the battery voltage. A drop in the battery voltage may be attributable to spontaneous discharging or to the connection of an external load to the battery. A check is also made in assessment block 14 whether the rest mode has lasted for a pre—determined number of days, for example 10 days. If this is not the case the rest mode will continue, as indicated by an arrow 16 in Fig. 1. If the rest mode has lasted for the specified interval of time a discharging phase 17 will be initiated, during which the battery voltage is measured and the battery is discharged at a constant current for an interval of time whose length is determined by the size of ' the battery. The battery voltage is measured in order to assess, as indicated by block 18 in Fig. 1, whether the battery voltage drops during the discharging programme below a pre—determined value, for example by 1.6% of the battery voltage when- the battery is fully charged. Should this not be the case the discharging phase will continue, as indicated by an arrow 19. Once the battery voltage has dropped below the aforementioned pre-determined value, the discharging phase is terminated and the charging programme is re—started, as indicated in Fig. 1 by an arrow 20 connected to the arrows 12 and 15. The battery is reconditioned during the discharging phase, and the charging method described above gives the battery an increased service life compared with conventional charging methods and guarantees that the battery is fully charged at all times. As before, the reference designation 1 is used in Fig. 2 to indicate the starting mode, and the designation 2 to indicate routine control measurements. The starting mode 1 is followed by a charging period, represented by a block 3 in the flow chart in accordance with Fig. 2. During this charging period charging of the battery takes place for a period of about 5 minutes at a voltage about 17% greater than the battery voltage. Charging is executed for an interval of time a consisting of a single number of minutes, preferably about 5 minutes. The block identified by the figure 4 indicates an option stage at which an assessment is made whether a considerably longer interval of time b in relation to the interval of time a has elapsed since the starting mode 1. The interval of time b amounts to a single number of days. If it is found at the optional stage 4 that an interval of time of the specified order of magnitude has not elapsed, the next stage in the flow chart is a measurement phase 5 during which, for a certain interval of time c, a check is made whether or not the battery voltage drops below a certain value. The interval of time c is of the same order of magnitude as, but less than the interval of time a, with an appropriate value being about 1 minute. If this is the case charging will take place in two stages, indicated by 6 and 7 respectively in the Figure, whereupon the assessment in accordance with 4 is repeated. During charging stage 6 charging of the battery will take place at an increased charging voltage for an interval of time d which is of the same order of magnitude as, but longer than the interval of time a...This increased charging voltage means that its value is of the order of 22% above the battery voltage, with an appropriate value for d being about 8 minutes. The following charging stage 7 involves charging at a normal charging voltage for an interval of time e which is of the same order of magnitude as the interval of time a, but is shorter than the latter; an appropriate value is about 2 minutes. The advantage of dividing up the charging operation into two stages in accordance with the above is that the following measurements are more reliable if charging at a normal charging voltage has preceded the measurement operation. If it is found during measurement phase 5 that the battery voltage does not drop below the aforementioned value U m -j n during the interval of time c, charging will take place in two stages, of which the first in Fig. 2 is designated by 8 and the second is identical with charging stage 3. During charging stage 8 charging of the battery takes place at a normal charging voltage during an interval of time f which consists of a single number of hours, preferably 3 hours. If it is found at assessment stage 4 that the interval of time b has elapsed since the starting mode 1, the charging cycle will enter a load phase 9 which is followed by charging stage 6. During the loading phase 9 ttie battery is subjected to resistive loading, either for a certain interval of time or until the battery voltage 1% has dropped to a pre—determined value Utø. The capacity of the battery determines the manner in which the load phase 9 is executed.

Claims: Patent Claims 1. A method for the cyclical trickle charging of a chargeable battery intended for emergency operation, in which case the charging voltage used is the output voltage from a source of d.c. voltage providing a variable level of output voltage, c h a r a c t e r i z e d in that charging from a starting mode (1) is executed in accordance with a cyclical charging programme (10) which is repeated until the battery has been found to be fully charged, in that a rest mode (13) then occurs during which the battery is not charged, but the battery voltage is measured continuously, in that the rest mode (13) is interrupted immediately, and the aforementioned charging programme (10) is re-started if it is noted in the course of. measuring the voltage that the battery voltage has dropped below a first pre—determined value, in that once the rest mode (13) has lasted for a pre—determined period, a discharging phase will be initiated which involves the battery being discharged in accordance with a discharging programme during which the battery voltage is measured continuously, in that the discharging phase (17) is interrupted if it is noted in the course of measuring the voltage that the battery voltage has dropped below a second pre—determined value, and in that once the discharging phase has been interrupted or completed, the charging programme (10) is re—started. 2. A method according to Patent Claim 1, c h a r a c t e r i z e d in that the charging programme (10) includes a number of different charging voltages, measurements and time intervals. 3. A method according to Patent Claim 1, c h a r a c t e r i z e d in that the pre—determined time interval is a single number of days. 4. A method according to Patent Claim 1 , c h a r a c t e r i z e d in that duri ng the di schargi ng phase (17) the battery i s di scharged at a constant current for an interval of time se lected depending on the size of the battery. 5. A method for the cyclical trickle charging of a chargeable battery intended for emergency operation, in which case the charging voltage used is the output voltage from a source of d.c. voltage providing a variable level of output voltage, said source of voltage being connected to the battery via a charging regulator, c h a r a c t e r z e d in that charging from a starting mode (1) is executed at a normal charging voltage (UR) for an interval of time (a) consisting of a single number of minutes, in that an assessment is then made of whether a small number or a large number of charging cycles has taken place, that is to say whether a considerably longer interval of -time in relation to the interval of time (a), preferably a- single number of days (b), has elapsed since the starting mode (1), in that, if this is/ the case, a check is made during a measurement phase (5) whilst the battery is subjected to load of whether the battery voltage (1%) drops below a certain value (U m -j n ) within a certain interval of time (c) of the same order of magnitude as, but shorter than the interval of time (a), in that, if this is the case, charging takes place at an increased voltage (Up) for an interval of time (d) of the same order of magnitude as, but longer than the interval of time (a) followed by charging at a normal charging voltage (1 ) for an interval of time (e) of the same order of magnitude as, but shorter than the interval of time (a), whereupon the aforementioned assessment is made once more, in that if the battery voltage (1%) does not drop below the aforementioned value (U m -j n ) within the aforementioned interval of time (c), charging takes place at a normal charging voltage (U |j ) for an interval of time (f) consisting of a single number of hours, whereupon the charging cycle reverts to the point after the starting mode (1), and in that if the considerably longer interval of time in relation to the interval of time (a) has elapsed since the starting mode (1) the battery will be subjected to load for a certain interval of time or until the battery voltage (Ug) has dropped to a pre—determined value, depending on the capacity of the battery, whereupon the charging cycle will revert to charging at the increased charging voltage (Up) during the aforementioned interval of time (d).

Inventors: WAHLSTROEM TOMMY, WAHLSTROEM, TOMMY
Applicants: WAHLSTROEM TOMMY, WAHLSTROEM, TOMMY
Application year: 1985
Main classification: H02J7
IPC codes: H02J7