HU209972B - Method for charging peroxide-zinck accumulators and charger circuit for implementing said method - Google Patents

Abstract

Each period of charging current (Ich) consists of a charging and discharging portion. The charging portion comprises a constant bias current onto which is superimposed a number of steep narrow current pulses. The ressistance-free battery voltage is measured each period and the time delay between charging pulses is decreased as the voltage increases. - The shorter discharge portion comprises a discharge bias current with discharging pulses displaced by a delay followed by a time when the battery is unloaded so that its voltage may be sensed.

Description

A charging circuit for charging alkaline manganese-zinc batteries is a controllable charge current generator (CHG) generating first and second specific output charging currents (ICH) in response to a binary control signal and a first and second specific discharge current in response to another binary signal. ) includes a controllable discharge current generator (DCHG), the outputs of the generators (CHG and DCHG) are connected to a rechargeable battery, includes a first timer (TI) output to the enable and inverse enable input of said generators (CHG and DCHG) ((, EN ) is switched on and alternately enables its current, and the charge current generator (CHG) has an enable time of at least five times that of the discharge current generator (DCHG), and includes a second timer (T2) controlled by the first timer (TI). time after which time the resistor voltage of the battery has become independent of the ambient temperature, this time is shorter than the enable time of the discharge current generator (DCHG) and the third timer for pulse input (tp) of said generators (CHG and DCHG) is at least 3-5 seconds (T3) is connected with a voltage sensor input connected to the battery, the charger circuit includes a bistable output comparator (CP), whose enable input (EN) is connected to the second timer (T2) output, the voltage sensor input is connected to the battery, (CP) has two reference inputs (refl, ref2) connected to each voltage source corresponding to the minimum and maximum threshold voltage, and the comparator (CP) output is connected to the stopping input (st) of the generators (CHG, DCHG) .

The present invention relates to a process for charging alkaline manganese dioxide zinc batteries during charging current.

It is known that the solutions used to charge the batteries differ in many ways and depend on the type, design and use of the batteries. However, all charging procedures require recognition of the fully charged state. A cathode-limited nickel-cadmium and nickel-zinc cell is known to have a reliable charge end detection method, which uses a voltage increase at the end of a charge in a steady state mode to indicate the completion of the charge. Such a filling procedure is described in U.S. Pat. patent.

Rechargeable manganese-zinc cells, due to their specific properties, need to be charged differently from other batteries.

The various properties of such batteries are disclosed in the " 14-19 " Summary of the Lecture on "The Technology of Rechargeable Alkaline Zinc Manganese Dioxide Batteries" at the Seventh Australian Conference on Electrochemistry, authored by K. Kordesch, D. Freeman and K. Tomantschger. With regard to the recharging of such batteries, the presentation emphasized that a non-resistive low-current charger could be considered an optimal solution. It was also noted that research and development in this area should be aimed at eliminating gas formation during the refill process and at reducing dendritic formation on the zinc electrode.

It is a primary object of the present invention to provide a charging method and charging circuit capable of meeting these needs.

In accordance with the present invention, there is provided a process for charging alkaline manganese zinc rechargeable cells by periodically sending specified charging and discharging currents to the battery during a successive series of charging and discharging steps, the charging stages being of substantially longer duration, as in the discharge stages and in each charge stage, a specific bias current and a varying width and intensity of pulses superimposed superimposed on the bias current are transmitted to the battery, whereby the pulses follow each other with a certain delay, and current and steep discharge current pulses of a specified duration and intensity superimposed on it. In each of the discharge phases, the discharge process is stopped after a specified time of at least 3 seconds, preferably 5 seconds, during which the battery voltage is detected and the charging and discharging process is stopped when the detected voltage reaches a certain maximum value, and varying the pulsating charge current depending on the detected battery voltage so that the energy decreases with increasing voltage.

In a preferred embodiment, the reduction of the charging current is solved by increasing the interval of the charging pulses as a function of the detected voltage.

HU 209,972 Β

In another embodiment, the interval of discharge pulses is also increased as a function of the detected voltage.

The optimum for cell life is to stop the periodic sequence when the defined first threshold level of the detected voltage is between 1.68 V and 1.78 V.

Automatic recharging can be provided by restarting the periodic sequence when the cell voltage drops below a second predetermined threshold level, e.g., 1.5V-1.65V.

The alkaline manganese dioxide-zinc cells with several types of life cycle is increased, when the charge pulse intensity is maximum three times the ampere-hours capacity of the battery corresponding to one tenth of current _I10. In such cases, it is advantageous if the prestressing current at the charge is less than or equal to the charge pulses.

Further preferably, the discharge pulses of at most a half times the I values from circuit _10, and if not more than half of the discharging bias current value with respect to the discharge pulses.

The present invention also provides a charging circuit for charging alkaline manganese zinc rechargeable batteries, characterized in that the circuit comprises a controllable charge current generator capable of generating a first and a second defined output current in response to a binary control signal. a controllable discharge current generator capable of generating a first and second output current of defined value in response to an additional binary control signal, wherein the outputs of the generators are connected to the rechargeable battery terminals, the circuit comprising a first timing unit which alternately enables said generators; the charge generator has an enabling time of at least five times as long as the discharge generator and the circuit includes a second timer unit activated by the first timer unit t, which provides a timer after which the resistance-free cell voltage has become independent of ambient temperature and is shorter than the start-up time of the discharge generator and has a third timing unit which is a binary pulse control of the generators for at least 3-5 seconds. connected to an input and generates binary signals that produce periodic pulses, the pulse duration of which is significantly less than the start-up time of the discharge generator, the voltage sensor input is connected to the battery, and a bistable output yes, the comparator also has two reference inputs, which refer to the minimum and maximum threshold voltage values connected to the voltage sources, the comparator output is connected to the stopping inputs of both generators, thereby allowing alternate charging and discharging processes if the cell voltage in the discharge periods after the second timer expires between the two reference values.

A preferred embodiment comprises a fourth timer unit enabled by the output of the second timer unit which provides a timer within the discharge periods that is at least as long as the transient processes within the battery required by the second timer unit during the discharge phase After the timer has been set, the output of the fourth timer unit is connected to the stop generator input of the discharge generator to stop the discharge process within the fourth timer, thereby bringing the battery to a no-load condition for the time the comparator is enabled.

The invention will now be described in more detail with reference to the drawings, in which: In the drawing it is

Figure 1 illustrates preferred current waveforms, a

Fig. 2 shows a major waveform of the arrangement of Fig. 8, a

Figure 3 illustrates the evolution of battery voltage over a full charge period with slightly distorted time scales;

Figure 4 illustrates the battery voltage during a charging and discharging period in an enlarged time scale,

Figure 5 illustrates a second preferred embodiment of the current waveforms, a

Figure 6 is a typical discharge time diagram, a

Figure 7 illustrates the charge capacity as a function of charge time with different charge times and cycle numbers, and

Fig. 8 is a functional block diagram of a charging circuit according to the invention.

Figure 1 shows the waveform of a periodic charge current of the present invention for rechargeable alkaline manganese dioxide zinc cells. Each such period consists of a charge and a subsequent discharge phase. In the exemplary case, the charging section consists of a duration of about 60 seconds and a constant current bias I _b and a plurality of steep current pulses superimposed on it. In the example, the narrow pulses were set to have a prescribed constant duration of 200 ms. The delay time t _d , interpreted between successive pulses, is considered an adjustable parameter and depends on the magnitude of the _unreinforced U _Rfree cell voltage sampled at certain times within each period. The maximum charge current I _{cb is} set to 2.4 times the cell's tenth capacity. In the exemplary case, C-type alkaline manganese dioxide zinc cells with a nominal capacity of 2.5 Ah were tested, so the charge current of I _{cb was} 600 mA. The magnitude of the biasing I _b was set to half the peak current I _cbm , i.e. 300 mA.

At the end of each charge cycle, a discharge cycle of approximately 10 s will begin. The discharge phase consists of two main parts, each of which is about 5 s long. In the first part discharge I _pieces

A bias current of about 0.2 x 10 _lo = 50 mA was generated and superimposed on 200 ms discharge pulses. The discharge pulses had peak current I p O _d, 8xI _lo, i.e. 200 mA. The delay time t _d between each pulse was equal to the value determined in the charge phase. If the delay time _{t d is} varied depending on the value of the _unreinforced sampled U _Rfree cell voltage, this change affects the repetition period of the pulses in both the charge and discharge periods.

In the second part of each discharge phase, the cell was not loaded at all. At the initial time of this unloaded portion (i.e., 1 or 2 ms after the cell current was discontinued), the cell voltage was measured, and this value formed the _unreinforced U _Rfree cell voltage. The interruption of the current eliminates the voltage drop that would occur due to the series resistance of the cell under load.

It is also shown in Figure 1 that an interruption of 0.5 s was initiated before the discharge phase started. This interruption was used to measure the unrestricted voltage of the cell immediately after the charging process was completed.

Figure 3 illustrates the change in delay time t _d between superimposed pulses as a function of the measured _unrestricted U _Rfree cell voltage. The delay time t _d maintains its original value until the cell voltage is below 0.7 V (Figure 3, Section A), and then the period time begins to increase (Figure 3, sections B and C). Initially, the higher charge frequency decreases and, on average, supplies energy with an average value close to that of conventional non-resistive chargers, which have been considered ideal for alkaline manganese-zinc cells.

In Figure 3, the time scale is distorted with respect to pulse duration. During the charging periods, the peak voltage of the pulses reaches its maximum value and at the peak during the discharge periods, it reaches the minimum at the peak of the load. The dashed lines represent the envelope of these two extreme voltages. The dotted line between them corresponds to the sampled resistance URfree cell voltage. The diagram also shows a decrease in the frequency of the charging pulses as the voltage increases. The sampled, unrestricted battery voltage gradually increases during the charging process, and this increase is sufficiently definite to complete the charging process when this voltage reaches the upper limit of 1.72-1.75 V.

When the charging process is complete, the unloaded cell voltage will begin to decrease. The charging circuit of the present invention resumes when the cell voltage drops below a lower limit, preferably between about 1.55 V and about 1.6 V. The charging process will now be shorter and the increase in sampled voltage will now be faster than when charging a discharged battery. The charger stops when the voltage reaches the upper limit. This process is constantly repeated, although the charging phases follow each other at increasing intervals and their duration decreases.

Figure 4 is an enlarged time diagram of the evolution of battery voltage, consisting of a charging and discharging phase as it appears at the output of a multichannel voltage recorder. The voltage peaks during the charge phase correspond to the current peaks of Fig. 1, and the low voltage values correspond to the bias between the pulses. During the discharge phase, similar but opposite voltage changes can be seen, but the envelope of the deep peaks and biases exponentially decreases after the charging phase is completed. It has been found that the shape of this decreasing curve is temperature dependent, and this dependence is greater than the onset of the discharge stages and then decreases rapidly thereafter. Our measurements confirmed that after 5 seconds after the start of the discharge phase, the battery voltage is practically independent of the ambient temperature. This fact justifies the choice of such a long waiting time that is required before sensing a resistor voltage. At each given temperature, the value of the resistance-free voltage sampled immediately after the completion of the charging cycles and the value of the voltage sampled 5 seconds after these times change in the same way throughout the charging process. It is worth noting that the battery voltage measured during the preload period changes similarly throughout the charging process and, consequently, the control of charge completion and pulse parameters may be based on this voltage value if sampled approximately 5 seconds after the completion of each charge cycle. It happens. Such samples contain a certain amount of error, which depends on the internal resistance of the battery. The charging of batteries with different internal resistances by such sampling is not as uniform as in the case of control based on the resistive measurement principle, since the voltage measured depends on the actual actual load current and the internal resistance of different values. However, for many uses, the resulting inaccuracy is well within the tolerable limits.

In addition to the charge current waveforms shown in Figure 1, experiments were also conducted with other waveforms. The current-time curves of these are illustrated in Figure 5. In this example, only the delay time t _d between the pulses superimposed on the bias current was changed by the change in the resistance-free voltage. In this current waveform, both the amplitude and the duration of the charge pulses were constant. The pulse width was 400 ms and the pulse amplitude corresponding to a maximum charge current of I _chm

HU 209,972 Β

600 mA was the equivalent of 2.4xI _z0 . The pre-tension I _{b was} 60 mA, i.e., O, 24xI _lo . The discharge section 50 mA, ie O, 2xi value _lo, the amplitude of the discharging pulses of I _ks precharge current is 300 mA, that is l and 2xi value _{of 10,} and the width remained impulusok 400ms. Charging the battery with such current waveforms is obviously a much more intensive process than using the waveforms of Figure 1. In each discharge phase, the active load lasted for about 5 seconds and was followed, as shown in Figure 1, by occasionally 5 seconds of no-load rest. The battery was sampled in the same way as in the previous example.

With the signal shapes shown in Figure 5, two series of manganese dioxide zinc rechargeable batteries of type C were charged. Each kit had 8-8 serially connected batteries. One channel of a multichannel recorder is connected to each battery. Charging was continued until the resistor-free voltage reached 1.72 V per cell. In the first cycle, the voltage reached this threshold in 7.25 hours. After about two hours of rest, the kits were discharged with a constant current of 190 mA. The discharge was completed when the cell voltage dropped to 0.7 V. Due to the serial connection of the eight batteries, the discharge process was actually stopped when the voltage dropped to 8x0.7 = 5.6V. The discharge time was 8.54 hours and the average capacity was found to be 1.62 Å. During this measurement we observed that the batteries are not the same. Figure 6 shows a typical discharge curve. In the second charge cycle, the charge time increased to 7.5 hours and the discharge time decreased to 8.5 hours, corresponding to a capacity of 1.61 Ah. In the third cycle, the charge time was 7.8 hours. In this case, the batteries were discharged with a 60 ohm resistor connected to each kit. With constant load resistance, the discharge time was 10.1 hours. Capacity was not calculated at this time.

The temperature of each battery was monitored during the charging process, but no change was detected. In contrast, the same batteries were previously charged with a conventional switching current charger, which allowed a constant voltage of 1.72 V and limited the maximum charge current to 1A. Here, during the first few hours of the charging process, an average increase of 3 ° C relative to the ambient temperature was observed. The charging circuit was left connected to the batteries for 28 hours and then discharged to an average capacity of 1.84 Å.

The experiments with the current waveforms shown in Fig. 5 were completed at this stage. Now, the waveforms outlined in Figure 1 are coupled to the two sets and a charging process is initiated, which was otherwise the fourth charge cycle with pulse charging. The charging end threshold was set to U _Rfree = 1.72 cell voltage. The charging process took 7.5 hours, followed by a 2 hour rest. A constant discharge current of 190 mA was then discharged for 8.4 hours and a capacity of 1.596 Å was obtained.

In order to make the capacity measurement more uniform, we selected similar behaviors from the two sets and assembled another set of eight identical batteries. With this new set we started an additional (fifth) cycle. Charging was completed after 7.5 hours in this cycle. The charging circuit was kept connected to the kit for an additional 2.5 hours while charging was automatically activated when the voltage dropped below 1.6 V for the two short periods shown in Figure 3. The 190 mA subsequent discharge lasted for 9.5 hours and had a capacity of 1.8 Ah. In the next (sixth) cycle, the charging stopped after 7.5 hours, at which point the charger was switched off and a rest period was started after resting. The discharge time was 7.5 hours and the capacity was 1,425 Ao. In the next (seventh) cycle, the threshold was raised to 1.74 V and was reached at the end of the 10 hour charge period. The subsequent discharge period was 9.58 hours and the capacity was 1.82 Ao. In the eighth cycle, the threshold was raised to 1.76 V and until this was reached, the charge lasted 11.5 hours. After two hours of rest, the discharge period lasted for 10.26 hours.

The results of experiments with the same charge current waveform but with different charge time are illustrated in Fig. 7 with diagrams showing the evolution of capacitance and associated charge times. In this figure, 100% corresponds to a nominal capacity of 2.5 Ah. A sixth cycle with a charge time of 7.5 hours corresponds to point J, while cycles 7 and 8 correspond to points G and H respectively.

For similar batteries, measurements using a resistive dc charging circuit showed that the first 50% of capacity was obtained by charging between 5.5 and 8 hours. This tolerance range is represented by the points A and B. Similarly, the charging times required to reach the two-thirds capacity ranged from 9 to 13 hours for points C and D. The area between the dashed lines connecting points A-C and B-D indicates the charging times at which the battery was charged at a percentage of the rated capacity on the vertical axis. We also observed that these times increase with the number of cycles. Points E and F correspond to points B and D, but their interpretation applies to cycle 20. We performed measurements at least between Cycle 7 and Cycle 9 (since we also performed an initial cycle with a decreasing current charger), and the resulting J, G, and H points were well above the expected range even if the first value assigned to the highest value was cycle expected value. Figure 7 shows that charging with current waveforms of the present invention achieves a more favorable charge efficiency.

In order to provide the battery with milder charging conditions, the threshold level was reset to 1.72 V, but the delay time t _d between the charging pulses was increased by about 40% (Figure 2 for the thus increased delay times).

EN 209 972 Β). The charging and discharging times and their respective capacity values for the following three (i.e., 9-11) cycles are summarized in Table 1.

cycle 9th 10th 11th charging time (h) 16.45 16.25 16.66 discharge time (h) 8.55 8.46 8.63 capacity (Ah) 1.625 1,607 1.64

The examples above show how the charge time varies with different waveforms. It will be appreciated that the optimum waveforms should and should be adjusted according to the requirements and requirements of the user and the characteristics of the batteries used. It is believed that the prestressing current in the charging sections is approx. It should be set at 100 mA, preferably 150 mA, at least for the first few hours of the charging period, after which the active state of the zinc electrode can be more advantageously ensured. Bias pulses superimposed on the preload help to draw more energy into the battery, and steep transient processes slow down the dendritic formation process, which increases cycle life. The use of voltage-independent voltage samples, which are highly independent of ambient temperature, for determining the end of charge cycles and for setting pulse characteristics, results in a more uniform charge. Automatic start and stop operation prevents gas formation when the charging circuit is left permanently on and repetitive cycles maintain (sometimes increase) the capacity without damaging the batteries or consuming excessive power.

Fig. 8 is a block diagram of a circuit arrangement according to the invention, which allows generating specific current waveforms for the charging process of the invention. In order to facilitate understanding, the timing symbols shown in Figure 1 are used in the explanation.

The circuit includes three timers T1, T2 and T3. The ATI timer generates a series of pulses that have a pulse time of 60 s and a pause of 10 s. These pulses define alternating recharging and discharging stages by connecting the timer output of TI directly to the enable input of the CHG charge current generator and the inverted enable input of the DCHG discharge current generator. Charging and discharging current generators CHG and DCHG have a stopping input which, when activated, interrupts outputs connected to one of the terminals of the battery to be charged. When the DCHG discharge current generator is enabled, a first constant load current is applied to the battery and a second constant load when a second enable condition is obtained at its pulse input tp. The CHG charge current generator operates in a similar manner and has a tp pulse input. The first current generated by the CHG charge current generator in the disabled state of the pulse input tp depends on the value of the second current generated in the enabled state of the pulse input tp, e.g.

The second timer T2 receives the output of the first TI timer and generates a low logic pulse of 5 s starting at the edge of the output pulse of the first TI timer that separates the charge and discharge stages. The output pulse of the second timer T2 is coupled to the EN enable input of the comparator CP made up of the window comparator and optionally to the EN enable input of the fourth timer T4. The CP comparator has bistable properties, so it retains the output state it took when crossing the first threshold in one direction until the signal crosses the other threshold in the other direction.

The operation of the arrangement is described with reference to the time diagrams of Figure 2. Referring to FIG. 2, the reference symbols of each time diagram correspond to those of the units in FIG. 8 where the illustrated waveforms are displayed.

During the first 5 seconds of each discharge phase, the output of the second T2 timer is in a logic zero (low) state (Fig. 2, T2 curve). Within 5 seconds, the output of the second timer T2 becomes high, enabling the comparator CP and triggering the timing of the fourth timer T4 (Fig. 2, CP and T4 curves). During the fourth T4 timer and typically 2 seconds timing, the DCHG discharge generator is disabled because it receives a stop pulse at its st stop input and the CP comparator state determines that the cell voltage is e.g. 1.72 and

It is within the window defined by the reference voltages ref and ref2 set to 1.6 V (Fig. 2 T4, U Rfree and DCHG curves). This can be considered as the cell's resistance-free voltage. During the CP comparator enable time, the cell voltage detected by the CP comparator is at maximum when no load current is present, i.e. when the fourth T4 timer on disables the discharge current. This period is shown in Fig. 2 by the shaded area of the U _Rfree curve.

The third T3 timer produces pulses of 200 ms width, the repetition time of which depends on the voltage of the cell.

The output of the third timer T3 controls the second enable input tp of both CHG and DCHG generators.

If a battery with a voltage of less than 1.6 V is connected between the battery terminals, the CP comparator turns on and interrupts the stop signal from the st stopping input of the generators, thereby initiating the alternating process of charging and discharging pulses and charging the battery. If the detected voltage exceeds the threshold of 1.72 V (which may occur during the non-resistive detection defined by the timing of the fourth T4 timer), the state of the comparator CP changes and stops both the CHG and DCHG charging and discharging current generators at their st stop input vezér6

HU 209 972 Β. The circuit arrangement thus provides all the conditions necessary to produce the current waveforms shown in Figures 1 and 5.

Claims (10)

PATENT CLAIMS CLAIMS 1. A method for charging alkaline manganese-zinc batteries, wherein a series of charging and discharging steps are provided with a specified charge or discharge currents for the battery, wherein the duration of the charging stages substantially exceeds the duration of the discharging steps. each driving a predetermined bias current to the battery and superimposed steeply varying charge current pulses of defined width and intensity, providing a delay between successive pulses, loading the battery with a predetermined bias current at a given biasing current and pulses are superimposed, each of the discharging periods having a discharge period of at least 3 seconds, preferably 5 seconds, interrupting, detecting battery voltage during the shutdown period, and stopping the charging and discharging process when the detected voltage reaches a specified maximum value and varying the pulsating charge current depending on the sensed voltage of the battery so that the energy decreases with increasing voltage. Method according to claim 1, characterized in that the amount of energy is reduced by increasing the delay time between the charging pulses in dependence on the detected voltage. 3. The method of claim 1, wherein the delay between discharge pulses is increased depending on the detected voltage. The method of claim 1, wherein the charging and discharging process is stopped when the detected voltage of the battery is between 1.68 V and 1.78 V per cell. The method of claim 4, wherein when the sensed battery voltage drops to a second defined threshold level per cell between 1.5 V and 1.65 V, the charging and discharging periodic sequence is restarted. The method of claim 1, wherein the intensity of the charging pulses is selected to be up to three times the current ( ₁₀ ) corresponding to one tenth of the numerical value of the battery capacity. Method according to claim 6, characterized in that during charging the prestressing current reaches at most half the value of the charging pulses. The method of claim 1, wherein the intensity of the discharge pulses is set to a maximum of one and a half times the current (I ₁₀ ) corresponding to one-tenth of the numerical value of the battery capacity and the discharge current is equal to at most half the discharge pulse. Charging circuit for charging alkaline manganese-zinc batteries, characterized in that, in response to a binary control signal to its pulse input (tp), a controllable charge current generator (CHG) generating first and second defined output charging currents (Ich) and another binary signal. in response, comprises a controllable discharge current generator (DCHG) for generating first and second specific discharge currents (Idch), the outputs of the generators (CHG and DCHG) being connected to a rechargeable battery, comprising a first timer (TI) output from said generators (CHG and DCHG ) is connected to its enabling and inverted enable input (ΕΝ, EN) and alternates its current, and the charging current generator (CHG) has an enable time of at least five times that of the discharge current generator (DCHG) and includes a second timer (TI) controlled (T2) the timing of which corresponds to the time after which the resistor voltage of the battery has become independent of the ambient temperature, which is shorter than the discharge time of the discharge current generator (DCHG) and lasts at least 3-5 seconds for said generators (CHG and DCHG). ) is connected to a pulse input (tp) of a third timer (T3) having a voltage sensor input connected to the battery, the charging circuit includes a bistable output comparator (CP) whose enabling input (EN) is connected to the output of the second timer (T2) connected to the battery, the comparator atoms (CP) have two reference inputs (refl, ref2) connected to each voltage source, which correspond to the minimum and maximum threshold voltage, and the comparator (CP) output to the generators (CHG, DCHG) stop bem is connected to his diet (st). The circuit of claim 9, further comprising a fourth timing circuit (T4) having its enable input (EN) connected to the output of the second timer (T2) and its output to the stop current (st) of the discharge current generator (DCHG). join.