Abstract:
Method for treatment, in the form of regeneration, of an accumulator ( 160 ) having at least one cell, preferably lead batteries, in which a varying direct current from a power source ( 130 ) is applied in intermittent current supply periods, which are interrupted by pauses of substantially less current, preferably current free, the direct current being sufficient to generate gas in the accumulator. During the treatment process, process data is registered, which process data is used in order to control the treatment process.

Description:
This application is a national stage entry filed under 35 U.S.C.371 of PCT/SE2005/001459 filed 4 Oct. 2005. This application also claims foreign priority under 35 U.S.C.119 and 365 from Turkish patent application No. 2004/02657 filed 12 Oct. 2004. 
     TECHNICAL FIELD 
     The present invention relates to a method and device for regeneration of accumulators having at least one cell, preferably lead batteries. 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 is sufficient to generate gas in the accumulator. 
     THE TECHNICAL STANDPOINT 
     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  and sulphate ions are taken from the electrolyte, which includes sulphuric acid. In principle, the process is reversed during charging. Conventionally, when being recharged by a continuous direct current, lead accumulators have a limited ability to be recharged. The reason for this is not completely investigated, but it is believed that influence is made by factors such as the products of discharge having a limited solubility in the electrolyte, or 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 risks being destroyed by inactive layers of lead sulphate that hinder the charging or decreases the capacity and 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. 
     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. The periods are between about 0.5 seconds and about 10 seconds. However, the technique described in WO 94/28610 is not adapted to all kind of batteries to be recharged, since it is not possible to control the charging process in a sufficiently satisfactory manner. 
     In WO 00/77911 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 is sufficient to generate gas in the accumulator, wherein said treatment constitutes a regeneration process. The current supply periods have a length of between 0.01 and 0.5 seconds. The current level during the current supply periods amounting to between 80 and 1000 A. The pauses have a length of 1-20 seconds. Process data for at least one cell in the accumulator is registered during the treatment process. The process data is used in order to control the treatment process. The method described in this application eliminates the major problems mentioned above, but still suffers from some drawbacks. 
     SHORT DESCRIPTION OF THE INVENTION 
     One object of the present invention is to offer a method for treatment, in the form of regeneration, of accumulators. The treatment process is controlled, in terms of current supply period, pauses and current strength, based on input data. This is achieved by the following steps: 
     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) adapting the amount of current during pulse in order to achieve more than 2.5 volt per cell and less than 3 volt per cell, in the peak of the pulse at open circuit voltage, and in between the pulses.
 
     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 converts crystals 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. 
     Other objects of the invention will become apparent during description of the preferred embodiment below. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
         FIG. 1  is a block diagram of a preferred embodiment of the method of regenerating a battery. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1  there is shown a block diagram of a preferred embodiment of a machine  100  according to the invention. The machine  100  preferably comprises a contactor  105 , for connecting to a supply of power, to supply a power source  130  within the machine  100 . The source  130  in turn feeds the transformer  140 , which in turn feeds a number of thyristors  120 . 
     In the preferred embodiment there are three pairs of double-thyristors  120 , i.e. in total six thyristors forming two sets. One set includes three thyristors in parallel to control one phase each on the positive side of the sinus curve and one set includes 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. 
     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 controls the trigger card  117 . As shown in the  FIG. 1 , the AC/DC converter  107  supplies 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 . 
     The machine  100  preferably includes a capacity testing unit  150 , comprising a thyristor  152  and a variable resistor  155 . 
     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, 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, with 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. 
     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 unit  150  is connected to the battery  160 , 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. 
     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. 
     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  controls 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 preset temperature level. If the temperature surveillance device  200  signals 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 the voltage level within each one of the cells in the battery so that the voltage level 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  signals 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 cells rises too high, too 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. 
     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. 
     The process will be preformed in basically exactly the same manner. 
     However, the treatment process is preferably performed in a number of cycles, e.g. 5-15 cycles, with each cycle including 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, to randomly change the level, such as every 10:th to 30:th second. For example, the current supply can be varied by starting with 60 A for 20 seconds, then 35 A 20 seconds, then 55 A 20 seconds, then 40 A 20 seconds, etc. 
     As mentioned above, 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 battery  160  is above 80% 5 cycles (of 9+1 hours) may be sufficient (total of 50 hours), whereas 10 cycles (6+1 hours=total of 70 hours) may be necessary for a battery  160  where the remaining capacity/condition of the battery  160  is less than 60%. 
     The control unit  110  may register process data, which can be accomplished 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 may be available to the control unit, for example via a network connection or locally stored data. 
     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 person, the different units of the machine  100  may 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 realizes 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 providing a small current to the battery  160 , that gives feed back to the control unit of the actual conductivity of the battery, which in turn may be used to better optimize the treatment. Furthermore, it is foreseen that each cell may be surveyed, not limited to treatment process, by measuring, for example, 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.