SE408610B - METHOD OF CHARGING DRY BATTERIES, AND ARRANGEMENT FOR IMPLEMENTING THE METHOD - Google Patents

Description

vaossog1-s * i i 2 stand increases and the voltage across the poles decreases. It is also conceivable that the internal resistance of the battery increases due to gas formation occurring in the electrolyte during discharge.

It is from a practical and economical as well as from an environmental protection point of view that batteries are discarded as soon as they have been soldered once, and the basis for the invention has therefore been the problem of providing a method and a device for charging or regenerating dry batteries of the said type. Extensive experiments have shown that recharging dry batteries is possible, and it has been shown that one and the same battery could be recharged at least about twenty times without the battery's capacity decreasing significantly compared to newly manufactured batteries. It has also been shown that even after a number of recharges, the dry batteries have a larger capacity than newly manufactured batteries, which are purchased on the open market.

In the method according to the invention, the batteries are thus charged with alternating current by applying the positive period of pulsating alternating current to the battery as an intermittent pulsating charging current, while during the intermittent periods between the charging current periods the battery is allowed to discharge slightly, preferably with a current between 5 and 20. % of the charging current, ensuring that the average value of the charging current through the batteries is kept as constant as possible throughout the charging period regardless of the state of charge of the batteries, however with any minor variations depending on the temperature or current sensitivity of the charging components.

As the internal resistance of the battery increases as the battery is discharged and the capacity is thereby reduced, a strongly discharged battery maintains a large internal resistance. If this resistance is large, it can be expected that the batteries cannot be recharged and it has been considered that it is not possible to charge batteries whose coil voltage has dropped more than about 10-20% L However, by ensuring that the charging current is maintained unchanged through the battery, a strong current will be applied to strongly discharged batteries, after which this current gradually decreases with the charging of the battery. In this way, a full charge of batteries can be achieved, the pole voltage of which has dropped at least down to 30% of the nominal pole voltage. Tables I-III below show an experiment with discharging and recharging dry batteries of type R14. Six newly manufactured such batteries were connected in series, the idle voltage being measured at 9.4 volts. The batteries were charged for discharge with 39 ohms, and with this load connected, the following values of voltage, current, power and internal resistance were obtained at specified times between 0 and 45 minutes. _ »Å ..., Å. = .. ,, _ \ ~. _. . 7805501 -9 3 T A B E L L In time voltage current effect internal res. my. volt mÅ W Ohm 0 8.4 210 1.77 1.13 5 3.0 200 _1.60 1.00 10 7.6 190 1.50 2.55 15 7.25 177 1.28 2.00 20 7 .10 167 1.18 3.50 30 6.78 164 1.11 2.27 35 6.67 160 1.06 2.40 45 6.38 154 0.98 3.50 After 45 minutes, the pole voltage on the the six series-connected dry batteries dropped from 8.4 to 6.38 volts, the current had dropped from 210 mA to 154 mÅ and the power from 1.77 W to 0.98 W. This decrease in the values is due to the internal resistance of the batteries f rose from 1.13 ohms to 3.50 ohms.

The same batteries were now connected for charging with the positive period of alternating current with 24 V voltage. During the extinguished intermittent periods, some recharging of the batteries was allowed, corresponding to about $ 20 of the charging current. During 45 minutes of charging, the batteries' voltage and charging current were measured, and these are reported in Table II below.

T A B E L L II time voltage current min. volt mA 5 8.6 83 10 9.0 85 15 9.65 125 20 10.0 125 25 10.0 125 30 10.4 108 35 10.6 105 4o '10.8 ms 45 11.0 100 * zrüß fi a -m * '' šiffn-.ßšæàtm fi itä “-Qwß.w + - a fi wàrümmmæšmwrv ru 78005501 -9 4 It can be observed that the voltage already after 5 minutes of charging was 8.6 volts and that after 45 minutes of charging it was 11.0 volts.

The charging current gradually increased from 83 to a maximum of 125 mA, after which it decreased slightly due to the charging current being counteracted by the battery bias in the used charger used, which will be described in more detail below.

The batteries thus charged were allowed to stand for three hours after charging was completed, during which time the voltage dropped slightly. After three hours, the idle voltage had stabilized at 10.00 volts, and this voltage was maintained for a long time to come.

A new discharge attempt was now made for comparison with corresponding values for newly manufactured batteries, which values are reported in Table I. The six series-connected batteries were also charged with 39 ohms in this case, and voltage, current, power and internal resistance were met periodically for 45 minutes.

T A B E L L III time voltage current power internal res. my. volt mA I W ohm 0 i 9.0 225 2.03 1.00 5 5.4 210. 1.77 1.00 10 3.0 zoo 1.60 1.00 15. 7.6 190 .. 1.44 1.00 20 * ra 7.25 183 '1.33 1.06 25 7.10 177 1.25 1.11 _30' 7.05 175 1.23 1, 28 35 5, 97 165 1.15 3.20 40 6.75 164 1.11 2.27 45 6.68 160 1.07- 02.79 As ..- f. uaa-iuemaxaaøasx 'i - vabsso1-9 5 It can be stated that the charged batteries consistently had a higher power and greater capacity than the newly manufactured batteries. To assess the battery's resilience, the 39 ohm load was disconnected, and the batteries were allowed to rest for one hour, after which a 39 ohm load was reconnected. After one hour of discharge, the batteries were found to have a voltage of 7.45 volts, a current of 1.85 mA, a power of 1.40 W and an internal resistance of 1.06 ohms.

The same batteries were subjected to a large number of discharges and charges, the discharges being carried out with varying loads.

Only after ten charges could a certain slowdown of the charge drill be felt. However, this was not greater than the fact that the batteries, even after recharging twenty times, could operate a transistor radio, a cassette recorder or the like without any remark. After thirty discharges and subsequent recharges of the same batteries and after the batteries had been allowed to rest for three days, the circulating voltage across the battery terminals was measured at 9.0 volts, which was thus only 0.4 volts lower than the corresponding domestic voltage across newly manufactured batteries.

Through various experiments, it could be established that the best charge is achieved if the charging voltage was approximately 33 1 above the nominal battery voltage and the charging current was between 75 and 175 mA. A lower charging current of 75 mA gave an unnecessarily long charging time without noticeable advantages, while a charging current of more than l75 mA risked giving an undesired power development in the form of heat in the batteries.

It should be noted that the charging current should of course be adapted to the type of battery, so that a battery with a larger capacity than the batteries of the type R14 discussed above is given a higher charging current than the one specified, while a type of battery with a lower capacity should be given a lower charging current. . Regardless of the battery type, the best value is obtained if the charging voltage is adjusted so that each cell of 1.5 volts nominal value is charged with 1.8 6 2.0 volts.

In the following, the invention will be further described with reference to a device for carrying out the method, which device is schematically illustrated in connection with the accompanying drawings. Figure 1 shows a wiring diagram of a simple device for carrying out the method according to the invention. Figure 2 shows a curve of the charging voltage drawn from an oscillograph. Figure 3 is a diagram schematically illustrating the voltage variations in a battery cell during charging in the charged but unloaded state and under load. Figure 4 shows in diagrammatic form the function of a zener diode connected in the device according to Figure 1, and Figure 5 shows a wiring diagram of a further developed and automatically functioning battery charger. '.__ ... Esa-m mt. .A - ~ fi e- r- »n fl- '- n ...

Sh! It is to be understood, however, that the method described and the embodiments of the invention described below and shown in the drawings are illustrative examples only, and that the invention is limited only by the concluding claims.

The device shown in the figure was the one used in the experiments described above, and the charging device contains a transformer (not shown) which supplies 24 volts AC voltage across the pole contacts 1 and 2.

Charging preferably takes place with the positive period of the AC voltage, and the device is adapted for the best possible charging of dry batteries of the type R14. From the pole contact 1 a diode D1, e.g. a silicon diode about. 0.5 A, connected, and parallel across the diode runs a large resistor R1 of 470 ohms and 1 N. The diode D1 and the resistor R1 run together in a wire 3, which is connected to the positive pole of six series-connected batteries 4 if each 1.5 volts. In the line 3 a small resistor R2 of 21 ohms and 9 W is connected, and in parallel across the series-connected batteries 4 a zener diode D2 with a breakthrough voltage of 12 is connected, partly also in series with this so-called PTC resistor (positive temperature coefficient) of between 0 and 100 kiloohm connected. The PTC resistor has the function of forming very high resistance when loaded with high current while the resistor decreases with decreasing current. This means that the PTC resistor provides high resistance when the batteries 4 have a high internal resistance, i.e. when the batteries are heavily discharged, after which the resistance of the PTC resistor decreases as the batteries become charged. From the negative pole of the battery runs a line 5, which closes the circuit at the pole contact 2.

The dry batteries 4 are thus intended to be charged with the, positive.-¿¿; periods of an alternating current, and during these periods a current passes from the pole contact 1, over the diode D1, through the line 3 and the small resistor R2 and through the batteries 4 and the current is closed through the line 5 to the pole contact 2. Since only the positive period is recovered the maximum voltage during the period half of the transformer voltage becomes 24 volts, ie 12 volts, which is 33 Z above the nominal voltage of the batteries. Because the resistor R1 is large, virtually all current passes through the diode D1. The zener diode D2 has a breakdown voltage of 12 volts, but a certain current nevertheless passes through the diode, and the higher the resistance in the batteries 4, the greater current would be passed through the zener diode D2 if it were not connected in series with the PTC resistor R3. If the batteries are strongly discharged, as mentioned earlier, the resistor R3 will be very high, and thereby practically no current will be able to pass through the unit of the resistor R3 and a. -.... »_ ,, _ H5- - .. _ - -saw- u. 7 'vaossrn-s zener diodes D2. Therefore, in the discharged state, the batteries 4 will be charged with a strong current, which is necessary to cancel the internal resistance of the batteries and thereby to provide a charging current through the batteries at all. As the charge increases, the internal resistance of the batteries decreases, and in step with this, the resistance of the PTC resistor R3 decreases. The resistor R3 thus balances the charging current, so that it remains substantially constant through the batteries 4 regardless of the state of charge of the batteries. Due to this design of the device, charging can be effected by batteries which are very strongly discharged, and charging has been successfully carried out by six series-connected batteries, the total pole voltage of which has been as low as 3 volts.

The function of the device is best seen in Figure 2, which shows three positive charge pulses 7 above the zero line and between these pulses discharge pulses 8, which represent the discharge allowed from the batteries during the periods between the charging pulses. In this case, it is assumed that six series-connected batteries are charged with the positive periods of alternating current, which periods have a maximum at 12 volts. In a charging pulse, the charging current thus passes for its main part through the diode D1, which may be a silicon diode, and through the small resistor R2, and practically all current enters the battery cells 4 as a charging pulse 7. After a charging pulse 7, the previous one is extinguished. negative pulse of the alternating voltage, and during the current gap thus formed the battery cells 4 are given an opportunity to discharge, a current pulse going from the battery cells 4 back over the small resistor R2 and the large resistor R1, since the diode D1 does not allow a current passage in this direction, and the current is closed over the edge contact point 1 and the transformer, over the contact point 2 and the line 5. The discharge pulse 8, which is opposite to the charging pulse 7, appears in an oscillating graph as a negative pulse 8. Because the discharge pulse 8 becomes substantially smaller than the charging pulse 7, the charge substantially remains the battery cells.

As the battery cells 4 are charged, the voltage in them rises, and during this increase an increasing proportion of the current of the charging pulse passes over the PTC resistor R3 and the zener diode D2, and only when the voltage across the battery cells 4 reaches the breakdown voltage of the diode D2, which in this case is assumed being 12 volts, the diode opens completely, and since the battery cells then do not receive additional charge, the resistor R3 increases its resistance and lowers the power outlet and the zener diode D2 is open, any current passing across the diode D2 and the resistor R3, and the battery cells 4 are thus disconnected from the charging circuit. The zener diode D2 and the resistor R3 in this way prevent a recharging of the batteries. If the battery voltage were to drop immediately, the zener diode D2 closes and the resistance increases in the resistor R3, and charge pulses are fed back into the batteries until the voltage across the batteries returns to the breakthrough rated voltage. Figure 2 illustrates in broken lines how the peaks of the charge pulses are cut off slightly as the voltage across the battery cells increases, and correspondingly illustrates how the voltage in the discharge pulses increases.

Figure 3 schematically illustrates the voltage function of a 1.5 volt battery cell during a charge, a subsequent rest period and a following discharge period. It is assumed in the diagram that charging begins when the battery cell has an idle voltage of slightly over one volt, and the charge is interrupted when the voltage across the battery cell has reached the desired charge level, which is assumed to be between 1.8 and 1.9 volts. As the charge is interrupted, the idle voltage of the battery drops for a short moment relatively rapidly to about 1.65 volts and for another one or two hours the voltage drops insignificantly until it has stabilized at a level which remains virtually unchanged for a long time. When the discharge begins, the voltage also drops relatively sharply for a short moment, after which the voltage drop takes place relatively slowly to a certain limit 9, when the voltage begins to drop at a slightly increased rate. It may be advantageous to recharge the batteries from point 9, but a recharging can also take place of significantly more discharged batteries.

The main purpose of the large resistor R1 is to limit the discharge current from the batteries, and the small resistor R2 is intended for adjusting the charging current for different types of batteries.

For batteries with a large capacity, a small resistor is used or the resistor R2 is completely excluded, oh, for batteries with a small capacity, one is used. y relatively large resistance. In the case described above, where six pieces. series-connected battery cells of the type R14 are charged, and where charging and discharging are reported in the above Tables I - III, the resistor R1 had 470 ohms, while the small resistor held 27 ohms. This gave a maximum charging current of about 150 mA charging current. The PTC resistor R3 had a working range between 0 and 100 kiloohm, and the zener diode times of the type IN 5927. To enable a charging of batteries of different ... if e. 11, - types, the resistor R2 can be designed as a rotary resistor, - an ammeter is then mounted in immediate connection therewith to check that the charging current is within the optimum value of 75-175 mA. s.-, - -e-.l- .n- - 9 7805501-9 -Figure zenerdiddenš Ü2 spark time fi is schematically illustrated with respect to the series-connected resistor R3 up to the break-through dark voltage l2 volts, and it can be seen that a relatively small current is able to pass in the breakthrough direction up to about 7 volts, after which a slightly increasing current passes up to 12 volts when the diode opens completely and the current can pass through the diode practically without resistance.

Figure 5 shows an alternative embodiment of a charging unit for carrying out the method according to the invention. This unit is intended to be connected to 220 volts AC, and it contains a transformer 10 which transforms down the current to a suitable charging current, e.g. 24 volt AC voltage for charging six series-connected dry batteries 4 of 1.5 volts each. A strong resistor R1 is connected to one pole terminal of the transformer and in series with this a weak resistor R2. In parallel, the resistor R1 is a diode D1, e.g. a silicon diode is connected, and a capacitor C1 is connected in parallel across the smaller resistor R2. The diode D1 and the capacitor C1 are connected at a point 11, and the output of the capacitor C1 is connected to the output of the small resistor R2 at a point 12.

Connected to the same point l2 are the butter cells 4 to be charged, a two-pole switch-on relay Rel, and a single-pole switch-off relay Re2. The opposite ends of the battery cells 4, the switch-on relay Rel and the switch-off relay Re2 are connected over a line 16, and in parallel across the battery cells 4 a zener diode D2 and a P1 mot resistor R3 are connected from point 12 to point 13. From point 13 three different lines are output, a line 14, which is connected to the terminal 2 of the transformer, and which contains a fuse 15, a line 16, which contains a control lamp L1, which indicates that charging is in progress, and a line 17, which contains a control lamp L2, which normally indicates that the batteries are fully charged. The lamps L1 and L2 are jointly connected to the pole terminal 1 of the transformer via a line 18, which contains a diode D3, which is connected with the anode to the pole terminal 1 of the transformer. In parallel across the switch-on relay a capacitor C1 is connected, and in parallel across the switching relay Re2 a capacitor C2 connected. Smoked from the transformer, the switch-on relay Rel is connected after the battery cells 4, and the switch-off relay Re2 after the switch-on relay Rel. In line 19, to which these parts are connected a diode D4 is connected between the battery cells 4 and the switch-on relay Rel, and between the switch-on relay and the switch-off relay a controllable resistor R4 is connected to enable a regulation of the switch-off voltage of the switch-off relay Re2. The two-pole switch-on relay Rel contains two contacts 19 and 20, which in the unaffected state of the relay are broken. The contact 19 is connected in the line 16 to the control. lamp L1, and the contact 20 is connected in line 14 to the transformer's .78fl55 Û1 9 m pole terminal 2. The single-pole switch-off relay contains a contact 21, which is connected in line 17 to the control lamp L2, and which is in an unaffected state. The diodes D1, D3, D4 can be of any suitable type, e.g. silicon diodes, while diode D2 is of the zener type and has a breakdown voltage which is about one third greater than the nominal voltage across the battery cells 4. When charging, for example, six series-connected battery cells of 1.5 volts each, where the nominal battery voltage is 9 volts, the zener diode should suitably have a breakdown voltage of 12 volts. Both relays Rel and Re2 have a permissible operating voltage which corresponds to the maximum charging voltage, ie in this case 12 volts, but at least the switch-on relay Rel should have a switch-on voltage which is at or below the lowest voltage at which an incipient charge is intended. to be able to start. As it has proved possible to charge six serially connected 1.5 volt batteries from a pole voltage as low as 3 volts, the switch-on relay Rel should therefore have a switch-on voltage of 3 volts. If the battery or a lower pole voltage than these three volts, the relay does not turn on, and contacts 19 and 20 remain broken, and no charge can occur.

The resistors R1 and R2 are adapted to the batteries to be charged, and when charging battery cells with 9 volt dark voltage, the resistor R1 is suitably selected to 470 ohms and the resistor R2 to 27 ohms. The resistor R4 is an adjustable resistor, which can be regulated, for example, between 10 and 2200 ohms, and the resistor R3, which thus constitutes a PTC resistor, can be selected for a working range between 0 and 100 kilohms.

To enable a request in the system if the batteries are fully charged, a resistor R5 can be connected via a switch 22 in parallel across the battery cells 4 as will be explained in more detail below.

The battery cells 4 are connected between the lines 19 and 16 with the anode facing the line 19. If the pole voltage across the batteries falls below the switching voltage of the switching relay Rel, its contact 20 in the main line 14 remains broken and no current can pass through the device.

Both control lamps L1 and L2 then remain off. If, on the other hand, the pole voltage across the batteries 4 exceeds the switch-on voltage, which in the above-related case was 3 volts, the relay Rel switches on, and contacts 19 and 20 are closed. 7805501 '-9 Charging: A current then passes from the pole contact 1 of the transformer through the diode DT, through the small resistor R2, through the battery cells 4 and back to the pole contact 2 through the main line 14. In parallel a current passes through the line 18, the diode D3, the control lamp L1, and back through the main line l4. Control indicator LI thus indicates that charging is in progress.

This current passes during the intermittent charging pulses.

Discharge: During the periods between dd intermittent charging pulses, a discharge current is allowed to pass from the battery cells 4, through the small resistor R2, the large resistor R1, over the transformer and through the main line 14 back to the battery cells 4. In parallel, a current breaks through the diode D4, through the switching relay Rel and back to the battery cells 4, which current keeps the main contact 20 closed.

The PTC resistor R3 and the zener diode D2 connected to it in series prevent any current from passing through it when the battery cells are strongly discharged. As the charge in the battery cells increases, their internal resistance decreases and thus the resistance in the resistor R3 also decreases, and some charging current can pass through the line 23 containing these parts.

Fully charged state: When the battery cells 4 are charged to a predetermined level, its counter-electromotive force becomes so great that the voltage across the battery poles amounts to the on-voltage of the relay Re2. Its switching voltage can be regulated with the controllable resistor R4. When this voltage is thus reached, the relay Re2 switches on, and the contact 21 in the line 17 closes, the control lamp L2 illuminating and thus indicating that the batteries 4 are fully charged. In this position, the resistance in the PTC resistor R3 has also risen to maximum resistance. the breakthrough voltage of the zener diode D2 has been reached.

All possible current will then pass partly through the line 23 containing the resistor R3 and the zener diode D2, through the switch-on relay Rel and the fully charging relay Re2. Thus, no overcharging of the batteries 4 can occur, and the device can therefore also be used for pure maintenance charging of dry batteries.

If the pole voltage in the battery cells 4 were to drop gradually, the resistance in the resistor R3 would increase, and a charging current would be caused to pass through the battery cells until they are fully charged again. At the same time breaks l t lay! few.

J .ïš ä "n .ag" n-wkg ..- ._._ ...-.... «.- ... alla .M-a. . ._-, ».. ~,., ..... a m ''. r 'mass -9 12 relay Re2 and thereby extinguishes the lamp L2, which indicates fully charged state.

It is obvious that the charging units according to the invention can also be used for charging rechargeable batteries and accumulators, e.g. rechargeable nickel, cadium accumulators or silver, zinc accumulators.

It is understood that the method described above and the devices described and shown in the drawings do not limit the invention without all sorts of different modifications may occur within the scope of the following patent body.

Claims (14)

A method of charging dry batteries, wherein the dry batteries are charged with one period of an intermittent pulsating alternating current, and wherein the batteries are allowed to discharge slightly during the periods between the charging pulses, characterized in that the charging current is balanced. the state of charge of the batteries so that the batteries, regardless of the state of charge, are charged with as constant an average value current as possible with any variations depending on the temperature or current sensitivity of the charging components. 2. A method according to claim 1, characterized in that the maximum voltage during the charging pulses is 25-35% higher than the battery rated voltage. 3. A method according to claim 1 or 2, characterized in that the dry batteries are allowed to discharge during the discharge periods with a current of 5 to 20% of the charging current. 4. A method according to claim 1, 2 or 3, characterized in that the charging current is adapted to 75 to 175 mA, which is maintained substantially unchanged by the batteries throughout the charge. Method according to one of the preceding claims, characterized in that the charge is limited by means of a zener diode and a PTC resistor connected thereto which are connected in parallel across the battery or batteries to be charged and with the cathode turned. against the positive current pole, the zener diode being adapted with a breakthrough voltage which is approximately 30% higher than the rated voltage of the dry batteries. IN Device for carrying out the method according to any one of the preceding claims, consisting of a transformer for down-transforming alternating current from the mains to a suitable charging voltage, a diode (D1) for emitting intermittent pulses of one period of alternating current, a parallel over diode (D1) connected resistor (R1), connections for one or more dry batteries (4) between the diode (D1) and the resistor (RI) on the one hand and a second pole contact (2) on the other hand, can be drawn in that the device has a zener diode (D2) and a PTC resistor connected in series therewith in parallel with the dry batteries (4), which is selected so as to balance the average charging current over the dry batteries (4), so that it is kept as constant as possible, wherein charging current pulses are now intermittently applied to the dry batteries (4) across the diode (DI), while an opposite discharge current arises during the periods between the charging current pulses, which no charge passes through m the resistance (R1). Device according to claim 6, characterized in that the zener diode (D2) has a breakthrough voltage which is approximately 30% * above the dark voltage of the dry batteries (4). Device according to Claim 6 or 7, characterized in that the resistor (R1) is adjustable for adjusting the discharge current so that it becomes 5-20% of the charging current during the charging periods (7). Device according to Claim 6, 7 or 8, characterized in that a charging resistor (R2) is connected in series with the discharge resistor (RI) and the dry batteries (4), which charging resistor (R2) is adjustable for adaptation. of charging current control for different types of dry batteries. ' 10. l0. Device according to potential claim 9, characterized in that a capacitor (C) is connected in parallel across the soldering resistor (R2). 11. ll. Device according to one of Claims 6 to 10, characterized in that it contains a switch-on relay (Rel), which switches on the charging current only when the pole voltage across the dry batteries (4) exceeds a certain set minimum value. 12. l2. Device according to claim ll, characterized in that it contains a control lamp (LI), which is lit by the switch-on relay (Rel) when this switches on. Device according to Claim 11 or 12, characterized in that it contains a fully charged relay (Re2) which switches on when the battery is fully charged, and which thereby ignites a second control lamp (12). _ Device according to one of Claims 6 to 13, characterized in that the PTC resistor (R3) has a working range between close to 0 and young. 100 kiloohm. SPECIFIED PUBLICATIONS: _ -g Technical journal. 107 (197?): 13, p. 41, 43 (Save the pocket-sized batteries 4 - they can have more than nine Lives). '