Patent Document

TECHNICAL FIELD 
       [0001]    The present invention relates to a method and device for treatment, in the form of regeneration, of accumulators having at least one cell, preferably lead batteries, in which a varying direct current from a charging unit, is applied in intermittent current supply periods which are interrupted by pauses of substantially less current, preferably current free pauses, the direct current being sufficient to generate gas in the accumulator. 
       THE TECHNICAL STANDPOINT 
       [0002]    In a charged lead accumulator, i.e. a lead battery, the active substance in the positive electrodes consists of lead superoxide, PbO 2 , and of porous metallic lead in the negative electrodes. When the battery is discharged, these active substances are converted to lead sulphate, PbSO 4 , sulphate ions being taken from the electrolyte, which include sulphuric acid. In principle the process is the reversed at charging. Conventionally, when being recharged by a continuous direct current, lead accumulators have, however, a limited ability of being recharged. The reason for this is not completely investigated, but it is supposed that influence is made by factors such as the products of discharge having a limited solubility in the electrolyte, it being considered that diffusion of the divalent lead ions constitutes the limiting factor both at discharging and recharging. Furthermore, lead sulphate is a very poor conductor of electricity. All these circumstances often result in problems in connection with the charging of lead batteries, which i.a. risks being destroyed by inactive layers of lead sulphate which hinders the charging or decreases the capacity, and which eventually makes the battery useless. In addition, there are problems in the form of different densities before and after the charging, which leads to the formation of sludge and to a decreased strength. 
         [0003]    In WO 94/28610, there is presented a solution to the above problems in connection with the charging of accumulators, especially lead batteries. According to this document, lead batteries may thus be charged by high current levels with a very good result and without a noticeable increase in temperature, when a direct current is being applied on the battery in intermittent current supply periods, interrupted by pauses in which no current is supplied, which periods are between about 0.5 seconds and about 10 seconds. 
         [0004]    However, the technique described in WO 94/28610 is not adapted to all kind of batteries to be recharged Neither is it possible to control the charging process in a sufficiently satisfactory manner. 
         [0005]    In WO00/77911 there is known method for treatment of accumulators having at least one cell, preferably lead batteries, in which a varying direct current from a charging unit is applied in intermittent current supply periods, which are interrupted by current free pauses, the direct current being sufficient to generate gas in the accumulator, wherein said treatment constitutes a regeneration process, wherein said current supply periods have a length of between 0.01 and 0.5 seconds, a current level during said current supply periods amounting to between 80 and 1000 A, said pauses have a length of 1-20 seconds, and wherein process data, for at least one cell in the accumulator, is registered during the treatment process, which process data is used in order to control the treatment process. The method described in this specification does eliminate the major problem/s mentioned above, but still suffers from some drawbacks. 
       SHORT DESCRIPTION OF THE INVENTION 
       [0006]    One object of the present invention is to offer a method for treatment, in the form of regeneration, of accumulators, the treatment process being controlled, in terms of current supply period, pauses and current strength, based on given input data. This is achieved by the following steps: 
         [0000]    a) measuring the available capacity of the accumulator to be treated by means of a capacity test,
 
b) adapting the parameters of said treatment in accordance with the result in step a),
 
c) using a first set of starting parameters if said capacity is above 80%, using a second set of parameters if said capacity is below 60% and using a further criteria to chose between said first and second starting parameters if said capacity is between 60%-80%.
 
d) adapt the amount of current during pulse in order to achieve more than 2.5 volt per cell, but less than 3 volt per cell, in the peak of the pulse, which are different from normal way of controlling battery voltage, at open circuit voltage, in between the pulses.
 
         [0007]    A basic object of the method and device according to the invention, is to achieve a regeneration of batteries which is non destructive to a battery, and convert crystal&#39;s of “hard lead sulphate” back to active material. The treatment process should moreover be adaptable and controllable for every single battery without causing mechanical damage. 
         [0008]    Other objects of the invention will become apparent during description of the preferred embodiment below. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
         [0009]    In the following, a device according to the invention, for the performance of the method according to the invention, will be described, while referring to  FIG. 1 , which is a block diagram of a preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    In  FIG. 1  there is shown a block diagram of a preferred embodiment of a machine  100  according to the invention. The machine  100  comprises a preferably a contactor  105 , for in supply of power, to supply a power source  130  within the machine  100 . The voltage source  130  in turn feeds the transformer  140 , which in turn feeds a number of thyristors  120 . 
         [0011]    In the preferred embodiment there are three pairs of double-thyristors  120 , i.e. in total six thyristors forming two sets, one set including three thyristors in parallel to control one phase each on the positive side of the sinus curve and one set including three thyristors in parallel to control one phase each on the negative side of the sinus curve respectively. It is evident for the skilled person that one set would suffice, but in such an embodiment the machine would merely be able to supply half of the power compared to using two sets. As indicated by  121  the thyristors  120  are connected to an accumulator  160  to supply a desired voltage and current to the accumulator. 
         [0012]    The thyristors  120  are controlled by a control unit  110 . In a preferred embodiment the control unit  110  comprises a PC,  112  (with conventional equipment, e.g. screen, mouse, hard drive, keyboard, etc.) and trigger card device  117 . As indicated the thyristors  120  are controlled by control signals  118  from the trigger card  117 . The trigger card  117  is in turn controlled by the PC  112  (sometimes the PC may control an intermediate control card which in turn is controls the trigger card  117 ). As shown in the FIGURE, there is arranged in AC/DC converter  107  to supply the electronics within the control unit  110  with power. Furthermore there is shown that the machine  100  includes a temperature surveillance unit  200  and a voltage surveillance circuit  180 . 
         [0013]    Furthermore the machine  100  preferably includes a capacity testing unit  150 , comprising a thyristors/s  152  and a variable resistor  155 . 
         [0014]    The control unit  110  controls the thyristors  120  to open and close a feed path  121  for electrical energy, supplied by the power source  130  (which in turn preferably is supplied by the common electricity supply network). The desired voltage and current for the process is controlled by the control unit  110  via the trigger card  117 , by controlling the phase angle and the opening time when trigging the thyristors  120  in collaboration with the transformer  140 . Moreover also the current is rectified by the thyristors  120 . Thereafter, the rectified current is supplied to the battery  160 , as a treatment by means of a tuned electrical energy, by continuously having feed back  191  for the supplied current from the current transducer  190 , feed back  181  for achieved voltage from the voltage surveillance circuit  180  and feed back  201  for temperature from the temperature surveillance unit  200 . According to the preferred embodiment the process is controlled during the whole process time, and adjustments of parameters are automatically set depending on the way battery is responding to the process. 
         [0015]    The battery is preferably charged from a discharged state. This discharge of the battery is preferably performed by a discharging unit  150  mounted within the machine  100 . By connecting  151  the discharging  150  to the battery  160  (which then should be for the charge) controlled total discharge of the battery  160  may be achieved. During this process information  153  is supplied to the control unit  110 , to control the actual capacity/condition of the battery that is to be charged. 
         [0016]    Thereafter the battery  160  is connected to the power feed  121  and also to the surveillance devices  180 ,  200 . The control unit  110  is thereafter provided with a number of starting parameters for the process that is adapted to the result of the capacity test. 
         [0017]    If, for instance for a 48-V battery (e.g. originally 560 Ah), the capacity test has shown that the remaining capacity/condition of the battery is above 80% of the original/starting capacity, the following starting parameters may be set in the PC  112  in a preferred embodiment, a current supply level of 350 ampere, a current supply period of 180 ms, and a pause of 2 seconds. Thereafter the process is started, and the PC  112  controlling the trigger card  117  to control the thyristors  120  to supply the set parameters to the battery. During the process the surveillance units  180 ,  190 ,  200  will continuously feed information to the control unit  110 . The current transducer  190  will give feed back  191  to the control unit  110  in connection with each supply period/pulse the exact amount of current within the pulse. In accordance with the invention the voltage within at least most of the cells of the battery  160  should reach at least 2.5 V during the pulse. If that feedback signal  191  identifies that the voltage in most of the cells of the battery  160  does not reach 2.5 volt, the control unit  110  will change the settings to increase the current level in a subsequent supply period, e.g. by 10 ampere. This control loop will continue until the measured voltage level reaches 2.5 volt, and under the condition that the temperature surveillance unit  200  has not provided input to the control unit  110  that the temperature is above a treasure level. If the temperature surveillance device  200  would signalise that the preset temperature level has been reached, without reaching the desired level of voltage, the control unit  110  will also increase the period of pause between two supply periods, in order not to let the battery reach a critical level of temperature. The control unit  110  also monitors that the voltage level within each one of the cells in the battery does not exceed 3 volt, since otherwise this may cause damages to the battery. Directly after termination of a supply period, the voltage surveillance  180  will give a feedback signal  181  to the control unit  110 . Hence, if the feedback signal  181  signalises that the threshold level of 3 volts is approaching, the control unit  110  will change the time of the supply period to be shorter, and/or lower the current level for a subsequent supply period. If voltage of the cell/s rises to high, to fast, the regeneration may be terminated and the discharge unit  150  may be used in order to reduce specific gravity and voltage, before regeneration is continued as usual again. 
         [0018]    If instead the capacity test has shown that the remaining capacity/condition of the battery is less than 60%, the following starting parameters may be chosen, a current supply level of 250 ampere, a current supply period of 180 ms, and a pause of 3 seconds. 
         [0019]    The process will be preformed in basically exactly the same manner. 
         [0020]    However, the treatment process is preferably performed in a number of cycles, e.g. 5-15 cycles, each cycle includes a regeneration part and a charging part, e.g. 6-9 hours regeneration and 1 hour charging. The regeneration part, for a battery  160  where the remaining capacity/condition of the is above 80% (i.e. when using said first set of starting parameters) is set to be longer (e.g. 9 hours) than for a battery  160  where the remaining capacity/condition is less than 60% (e.g. 6 hours). The charging part may be set to be substantially the same independent of the capacity/condition of the battery  160 , e.g. 0.5-2 hours. Preferably the current level during charging is less than half of the current level during regeneration, e.g. 40-70 A. Moreover a variable current supply during charging, has shown to be beneficial, i.e. to alternate the current level during charging, e.g. to randomly change the level, e.g. every 10:th-30:th second, for example to start with 60 A for 20 seconds, then 35 A 20 seconds, then 55 A 20 seconds, then 40 A 20 seconds, etc. 
         [0021]    As mentioned the regeneration part when using the first set of parameters will be longer compared to using the second set of parameters. In other words a battery  160  having a good remaining capacity/condition may be regenerated “tougher” than a battery  160  having a poor remaining capacity/condition. This leads to a quicker improvement of a battery  160  having a good remaining capacity/condition, which in turn leads to less cycles being necessary. For instance, for a battery  160  where the remaining capacity/condition of the is above 80% 5 cycles (of 9+1 hours) may be sufficient (totally 50 hours), whereas 10 cycles (6+1 hours=totally 70 hours) may be necessary for a battery  160  where the remaining capacity/condition of the is less 60%. 
         [0022]    The control unit  110  may register process data, which e.g. by means of the temperature and conductivity surveillance  200  and the voltage surveillance circuit  180 . The control unit  110  may also make use of general data for the specific battery, for the control, as well as older process data and general data, which are available to the control unit, e.g. via a network connection or locally stored data. 
         [0023]    The invention is not limited by the above described embodiments, but may be varied within the scope of the claims. As its evident for the skilled man the different units of the machine  100  must not be stored within one and the same vessels/housing. For instance, as is evident for the skilled person in the art the discharging unit  115  may be a separate unit, as also the control unit  110  and/or the surveillance units  180 ,  200 , to be used separate in a connecting network or as modular units that may or may not be assembled. It is evident to the skilled person that the different connections between different units of the machine  100  may be designed in many different ways, e.g. as is know per se, that digital information signals may be transmitted wireless as or by wire or by optical means. Furthermore the skilled person realises that many variations from what have been described in the examples given, may be made without departing from the concept according to the invention, e.g. to use it in relation to one phase current (then merely one thyristor or one double-pair being needed), to use different sets of starting parameters, etc. Moreover it is evident for the skilled person that the process may be further supplemented by adding a conductivity surveillance unit, which preferably may be integrated within circuit  180 . This may be achieved by super posing a small current to the battery  160 , that gives feed back to the control emit of the actual conductivity of the battery, which in turn may be used to better optimise the treatment. Furthermore it is foreseen that each cell may be surveyed, not limited to treatment process, by measuring e.g. conductivity, voltage, temperature and specific gravity, e.g. by means of wire less sensor units within each one of the cells. It is evident that such an arrangement would provide for even better surveillance during a treatment according to the invention and also for improved surveillance during use of the battery.

Technology Category: 4