WO1981001488A1

WO1981001488A1 - Apparatus for recharging of batteries by means of pulsating current

Info

Publication number: WO1981001488A1
Application number: PCT/SE1980/000277
Authority: WO
Inventors: K Roestlund
Original assignee: Bele Invent Ab
Priority date: 1979-11-21
Filing date: 1980-11-06
Publication date: 1981-05-28
Also published as: IL61457A0; GB2065998A; BE886166A; PL228007A1; ZA807084B; ES497038A0; SE7909623L; NO803506L; PT72070A; JPS56501905A; IT8050209A0; DD154659A5; FR2470467A1; IT1145316B; DK496280A; FI803641L; PT72070B; BR8008919A; SE419147B; ES8106988A1

Abstract

An apparatus for recharging dry batteries or accumulator batteries by means of pulses of alternating current or any other type of intermittent pulses and for a slight discharging of the batteries or accumulators during the periods appearing between the recharging pulses and comprising a mains connection circuit (A) and a recharging circuit (B) connected thereto having terminals for one or more batteries to be charged and a rectifying means (8) supplying a direct current to a controllable guide means (19). The apparatus comprises a control unit (C) which is connected to the guide means (9) and which defines the moment (75) of the alternating current pulse or the other intermittent pulse when the recharging circuit (B) is activated and a recharging voltage is supplied to the battery (13). The guiding means (9) may be a tyristor which is made conducting by the control circuit (C) at a predetermined moment (75). The control circuit (C) comprises means for optional continuous or stepwise controlling of the trigging moment (75) for the recharging pulse during the extent of the recharging and thereby for controlling the length of the recharging periods and the intermediate discharging periods. The apparatus comprises means for changing the level and the duration of the recharging voltage during the recharging operation especially after a given recharging period by increasing the recharging voltage and concurrently therewith move the trigging point (75) for the recharging pulse so that the duration of the recharging period is reduced and the duration of the discharging period is increased.

Description

Apparatus for^' recharging of batteries by means of pulsating current

The present invention generally relates to an- apparatus for recharging of dry batteries and accumulators, and more particularly the invention relates to an apparatus for recharging the dry bat¬ teries or accumulators by means of intermittent pulses preferably alternating current pulses, whereas the batteries or accumulators are allowed to slightly discharge during the periods intermediate the recharging pulses.

An ap-paratus for recharging of dry batteries or accumulators by means of pulsating alternating current is previously known from the Swedish patent 78 05501-9. For the purpose of adapting the ave¬ rage recharging current over the dry batteries or accumulators the said previously known apparatus comprises a Zener-diode which is connected parallelly over the batteries or accumulators and a PTC (Positive Temperature Coefficient) resistance connected in series with the Zener-diode and chosen so as to give an average recharging current which is as constant as possible, and whereby recharging pulses are intermittently supplied to the batteries over a diode, whereas a counter directed discharging current appears during the periods between the recharging current pulses. The PTC-resistance functions so that it is blocked at a low counter-electromotive force (EMF) from the batteries thereby forcing all current to pass through the batteries. At a high counter-E F the PCT resistance successively opens to allow an increasing portion of the current to pass, so that thereby a successively reduced portion of the current passes through the batteries or accumulators.

The said previously known apparatus gives a very good result and is well suited for recharging of dry batteries and some small types of accumulators. On the contrary the known apparatus cannot be utilized for recharging of large batteries which need high re¬ charging currents since the PTC-resistances at present available on the market can only stand such small current intensities as up to 1 amperes at the maximum.

Other previously known battery recharging apparatus have i turn a restricted possibility of recharging batteries to over 70 of the battery capacity and for making such recharging possible current intensities must be utilized which are substantially hig than the maximum current intensities than the said PTC-resistanc can stand.

Many battery recharging apparatus also have a relatively l efficiency and are designed so that heat is developed in the bat cells what may damage the cell and causes a development of harmf vapors or detonating gas.

The object of the invention therefore is to solve the prob of providing an apparatus for recharging of dry batteries and especially accumulator batteries by means of intermittent pulses preferabl .alternating current pulses, in which the batteries are recharged by means of the said intermittent alternating current pulses whereas they are allowed to slightly discharge during the periods appearing inbetween the recharging pulses and in which hi current intensities can be utilized without damaging the accumula tor batteries or the components included in the recharging appara tus.

Another object, of the invention is to solve the problem of viding a recharging apparatus having a high"efficiency and operat substantially completely without the development of heat in the battery cells and in which the risk of. the appearance of harmful vapors and detonating gas is eliminated or at least strongly re¬ duced. The invention also intends to provide a battery recharging apparatus which is designed completely safe in that the output re charging terminals are current less before the battery to be char is connected and which becomes current less as soon as the batter is fully recharged. A further object of the invention is to solve the problem of providing an alternating current apparatus in whic the recharging current intensity can be controlled within wide ranges, for instance from 2 amperes and practically without any upper limit.

According to the invention the apparatus comprises a contro lable current directing means and a controllable trigger circuit which is controlled by the current directing means so as to ignite and letting one of the alternating current pulses through of one or more batteries or accumulators. The trigger circuit comp¬ rises a rectifying means giving a substantially constant operating voltage to a time controlling means which controls the time of igniting the current directing means. The apparatus also comprises means for allowing some discharging during the periods appearing between the ^'recharging pulses.

By utilizing a current directing means which is controlled by the trigger circuit it has been possible to foresee that only the intended periods of the alternating current is let through for re¬ charging of the battery, and by utilizing a time controlling means which control the time when the current directing means is ignited it is possible to control the ignition moment between 0° and 180° of the period thereby varying the recharging current intensity from maximum recharging current intensity down to practically no re¬ charging current intensity at all.

Further characteristics -of the invention will be evident from the following detailed specification in which reference will be made to the accompanying drawings.

In the drawings figure 1 shows a block diagram of an apparatus according to the invention, and figure 2 shows a circuit diagram of an apparatus according to figure 1. Figure 1 diagrammatically shows the recharging function of the apparatus according to figure 2 and figure 4 diagrammatically shows a corresponding recharging function of a modified embodiment of the recharging apparatus. Figure 5 shows a modified circuit diagram- of a recharging apparatus accor¬ ding to the invention and figure 6 shows more in detail a circuit diagram of a- controlling means included in the apparatus accor¬ ding to figure 5. Figure 7 diagrammatically illustrates an alterna¬ tive method of recharging batteries or accumulators by means of the apparatus according to figures 5 and 6. The apparatus diagrammati¬ cally illustrated in figure 1 comprises a mains connection circuit A to which is connected a recharging circuit B having terminals for the battery to be charged. The recharging circuit B is controlled by a controlling circuit C and it is adapted to be connected for re¬ charging by the assistance of a switching in cirGuit^'.D. For- main¬ taining a stable and an exactly predetermined voltage the recharging circuit is connected to a voltage stabilizing circuit E and for disconnecting a fully recharged battery the recharging circuit is

SUBSTJTUTE SHEET connected to a disconnection circuit F.

As conventional the mains connection circuit comprises a fu 1, a main switch 2 and a transformer 3 for stepping down the alte nating current voltage of the mains to a suitable recharging volt Parallelly over the transformer 3 are connnected a capacitor and transient protector in the form of a varistor 5. From one termin 6 of the mains connection circuit a main conduit 7 leeds to the r charging circuit which in series comprises a diode 8, a controlla. current directing means in the form of a tyristor 9, a fuse 10 an a controllable resistance 11. From the resistance 11 one pole: te nal 2 of the battery or accumulator 13 to be charged is connected. The second pole terminal 14 for the battery or accumulator is con nected to a return conduit 15 leeding to a second terminal 16 of the mains connection circuit. Both the diode 8 and the tyristor are connected with the anode directed to the terminal 6 of the ma connection conduit and with the cathode directed to the input pole terminal 12 of the battery. In^* the return conduit 15 from the out put terminal 14 of the battery an amperemeter 17 is connected. Fro a point of the main conduit 7 between the fuse 10 and the control¬ lable resistance 11 to a point succeeding the amperemeter 17 in th return conduit 15 a cooling fan 18 is connected. Parallelly over the tyristor 9 is connected a diode 19 in series with a resistance 20. The said circuit is intended to transmit a slight current past the tyristor 9 so that the cooling fan "18 is supplied with cu rent even when the tyristor 9 is inactive. Between the controllab resistance 11 and the input battery pole terminal 12 a switch 25 f the switching in circuit is connected as will be explained closer the following.

The controlling circuit C is connected to the recharging cir cuit D over a rectifier bridge 22 which is connected parallelly ov the tyristor 9. At the positive terminal of the rectifier bridge conduit 23 comprising a matching resistance 24 is connected. The conduit 23 branches into a first conduit branch 25 comprising a resistance 26 and the conduit branch 25 in turn branches into two conduit branches 27, 28, one of which is connected to the anode an the other to the gate of a PUT-transistor 29 (Programmable Unijec- tiontion Transistor). The conduit 27 to the PUT-transistor 29 com prises in series a resistance 30 and a controllable main resistanc 31 by means of which the recharging current can be controlled. Th purpose of the resistance 30 is to prevent a current surge short-circuiting of the PUT-transistor 29 when the main resistance 31 is turned to its zero-position. The second conduit branch 28 com¬ prises a controllable balancing resistance 32 which is adjusted match¬ ing the PUT-transistor 29 so that the said transistor gives a suit¬ able recharging current intensity. Parallelly over the gate and the cathode of< the PUT-transistor a second balancing resistance 33 is connected in series with a trimming resistance 34. From a point between the balancing resistance 33 and the trimming resistance ^*3^'4 a conduit 35 leeds to the negative terminal of the rectifier bridge 22. Parallelly over the trimming resistance 34 and the anode of the PUT- transistor 29 a trigger capacitor 36 is connected which defines the point when the PUT-transistor 29 ignites the tyristor 9, whereby the trigger capacitor 36 defines the ilength, width and height of the recharging pulse. From a point on th;e conduit 23 between the resis¬ tances 24 and 26 to a point on the conduit 35 subsequent to the trig¬ ger capacitor 36 a Zener diode 37 is connected. The controllable resis- tance 34 connected to the cathode of the PUT-transistor 29 is with the output 38 thereof connected to the gate 39 of the tyris¬ tor 9 over a diode 40 having the anode thereof connected^' to the out¬ put of the trimmer resistance 34 and the cathode connected to the gate 39 of the tyristor. Between the diode 40 and the gate 39 a switch 41 of the disconnection circuit F is connected as will be explained closer in the following.

The switching in circuit D is connected' directly over the ter¬ minals 12 and 14 of the battery and it comprises a conduit 42 in¬ cluding two current directing diodes 43 and 44 having the anodes tur¬ ned to the pole terminal 12 of the battery and the cathode of the latter diode 44 connected to a switch in relay 45. The opposite ter¬ minal of the relay 45 is over a diode 46 and a resistance 47 con¬ nected to the second pole terminal 14 of the battery. The relay 45 is formed with a switch 21 which is connected between the resistance 11 and the terminal 12 of the main conduit 7. In non-activated state of the relay 45 the switch 21 is disconnected and the recharging current to the battery thereby is disconnected.

Parallelly over the relay 45 the voltage stabilizing circuit E is connected. The said circuit comprises a rectifier bridge 48 which with the alternating current terminals is connected to the transfor¬ mer output over a first conduit 49 comprising a switch 50 and a re- sistance 51 and a second conduit 52 comprising^' a resistance 53. negative terminal 54 of the rectifier bridge 48 is connected to t output of the relay 45 over a conduit 55. A capacitor 56 is conn ted parallelly over the negative terminal 54 and the positive term nal 57 of the rectifier bridge 48. From a point between the capac tor 56 and the positive terminal 57 a conduit 58 is connected whic includes a resistance 59 and a voltage stabilizer 6 which gives a stable smoothed direct voltage. The conduit 58 is connected pa^'ra lelly over the negative and positive terminals 54, 57 of the rect fier bridge 48. From the voltage stabilizer 60 a conduit 68 leeds back to the positive terminal of the relay 45 over a fuse 62 and diode 63. From a point between the voltage stabilizer 60 and the fuse 62 a capacitor 64 is connected to the conduit 55. Between th conduits 42 and 15 a transient protection in the form of a diode 6 is connected.

The disconnection circuit F is connected parallelly over the

- switching in circuit D between the conduits 42 and 15. In the con duit 42 a variable resistance 66 is connected, and from said resis tance to the conduit 15 a double relay 67 is connected. The relay comprises a first switch 41 which normally is closed and which is connected between the relay 40 and the gate 39 of the tyristor and a second switch 68 which is connected in a conduit 69 across the m conduit 7 and the return conduit 15 and which includes a signal bu 70. At the positive terminal of the relay 67< a conduit 71 is con¬ nected which includes a normally closed switch 72 and a diode 73 which with the anode is connected between the fuse 62 and the diod 63 in the conduit 61 from the voltage stabilizer 60.

The above described apparatus operates as follows: For connecting the apparatus the switch 2 is closed whereby current from the secondary side of the transformer 3 leeds both through the conduit 69 with the signal bulb 70 and over a bridging conduit 79 having a resistance 80 which bridges the switch 68 of the relay 67 and also past the tyristor 9 through the bridging con¬ duit including the diode 19 and the resistance 20 and further through the cooling fan 18. Consequently the signal bulb 70 and th cooling fan 18 are always actuated when the main switch 22 is con¬ nected. A current also leeds from the cathode of the diode 8 to th rectifier bridge 22 and from there to the Zener-diode 37 and the

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C?.'F time controlling circuit with the PUT-transistor 29. The Zener- diode 37 gives a constant- operation voltage to the said circuit. The

<- mam resistance 31 in connection with the trigger capacitor 31 de¬ termines the time when the PUT-transistor 29 ignites the tyristor 9 . over the gate 39 thereof. Since the switch 41 is normally closed recharging pulses can move as far as to the said gate 39 as long as the switch 41 ^'is disconnected what is made by means of the disconnec¬ tion relay 67. Since, however, the switch 21 is normally disconnec¬ ted no charging of the battery 13 can be made until the relay 45 is activated. If the battery 13 is not completely discharged the remaining current of the battery is sufficient for activating the switching in relay 45 in that a current passes in a circuit from the terminal 12 of the battery through the diodes 43 and 44, the re¬ lay 45, the diode 46, the resistance 47 and back to the second ter¬ minal 14 of the battery. When the relay 45 is thus connected the switch 21 closes and recharging pulses can pass from one terminal 6 of the transformer through the main conduit 7, the diode 8, the ty¬ ristor 9, the fuse 10, the resistance 11 and through the battery_, 13 and back through the return conduit 15 to the second terminal 16 of the transformer. Recharging current pulses go to the battery du¬ ring the moments when the tyristor 9 is ignited what is made by the controlling circuit over the gate 39. During those periods which appear between the recharging current pulses the battery is allowed to discharge slightly in that a current goes from one terminal 12 of the battery through the resistance 11 and through the conduit with the cooling fan 18 back to the second terminal 14 of the battery. Such recharging periods are of essential importance for the rechar¬ ging of the battery.

If the battery should be very strongly discharged so that the remaining current thereof is not sufficient to activate the switching in relay 45 the recharging can be started in that the switch 50 of the co^'nduit 49 is closed whereby a primary current goes through the resistance 51, the conduit 49, the rectifier bridge 48 and back through the resistance 53 of the conduit 52. A rectified secondary current thereby passes from the negative terminal of the switching in relay 45 through the conduit 55, over the terminals 54 and 57 of the recti^¬ fier bridge, through the resistance 59, the voltage stabilizer 60, the capacitor 64, the fuse 62 and the diode 63 back to the positive terminal of the relay 45, whereby the relay 45 is activated and the

$' ^ ^ u - - switch 21 is closed. When the battery 13 is fully recharged and t counter EMF thereof has reached a certain level a current through the conduit 42, the diode 43 and the resistance 66 will pass throu the disconnection relay 67 and back to the return conduit 15 over the resistance 47. The disconnection relay is thereby activated a the switch 41 in the conduit from the time controlling means is opened whereas the contact 68 in the conduit having the signal bulb 70 is closed. Thereby the pulses to the gate 39 of the tyristor 9 are cut off and a recharging current can no longer pass through the battery 13, and the signal bulb 70 will light with a higher effect".

If the battery 13 is strongly discharged it may happen that also the disconnection relay 67 is activated to the effect that the switch 41 is opened. To avoid this the switch 72 is opened so that the current over the relay 67 from the voltage stabilizer circuit i cut off.

Figure -3 diagrammatically .illustrates the recharging of the battery 13. It is presupposed that the recharging is made with the positive pulses 74a of a periodically alternating current and that some discharging is allowed during the negative pulses 74b of the same periodically alternating current. By controlling the main resistance 31 the point 75 at which the tyristor 9 is trigged can be moved to any chosen position between 0 and 180 of the positive pulse and the recharging does not start until the tyristor 9 is ig¬ nited when being trigged. The portion 76 of the pulse 64a precedin the trigging point 75 allows, a discharging and only the portion 77 of the pulse succeeding the trigging point 75 gives a recharging of the battery. Since the discharging in this case is made by the coo ling fan 18 which has a relatively high resistance the discharging 78 is made only with a slight amount, for instance 1 - 2 % of the recharging current. By moving the trigging point 75 by controlling the main resistance 31 the recharging can be made with any intended current intensity from maximum recharging with the trigging point located at 0 to no recharging at all at 180

By utilizing a transformer having a central terminal and usin two diodes of substantially the same coupling type as in Figure and by utilizing a so called triak coupling it is possible to reverse the negative pulse portion 74b as illustrated in Figure 4 to a positive recharging pulse 74a' . Still a discharging is allowed

Ga^'PI , , 75' .

Figure 5 diagrammatically shows an alternative apparatus accor¬ ding to the invention for recharging of dry batteries or accumula¬ tor batteries. The apparatus comprises a transformer 3' which on the secondary side is designed with double output terminals or en¬ abling a switching over of the recharging voltage from one level to another as will be further explained in the following. From the secondary side of the transformer 3' two diodes 8a and 8b are con¬ nected which each let throu'gh one halfperiod of the periodical al¬ ternating current so that a continuous train of positive pulses are obtained. The diodes 8a and 8b give a current to the tyristor 9 whereby the current in a main conduit is supplied to one battery terminal 12 over a resistance 82. From the other battery terminal 14 the current is returned through conduit 83 to the central point at the secondary side of the transformer. From the main conduit 81 current is directed to the controlling circuit C which will be ex¬ plained more in detail in the following.

The apparatus comprises a circuit 84 applying a load which pro¬ vides a reversing of the current during the periods when there is no recharging so that the apparatus gives a discharging during the said reversed current periods. From point 85 a control voltage is supp¬ lied to the said load circuit 84 over a resistance 86 to the base of a transistor 87 which connects a resistance 90 connected to the pole terminal 12 of the battery. In order to assure that the transis¬ tor 87 closes when the guide voltage at point 85 ceases a resis¬ tance 91 is connected between the base of the transistor 87 and the return conduit 83.

For giving a smoothed direct current a capacitor 92 is connec¬ ted between the main conduit 81 over a diode 93 to the return conduit 83. This circuit gives a drive current to a relay 94a having two switches 94b enabling a switching over of the secondary side of the transformer 3' between two different voltages. It is obvious to the expert that the relay including the switches by conventional couplings alternatively can be designed for successively varying the voltage on the secondary side of the transformer.

In Figure 5 the different terminals of the controlling circuit C of the recharging apparatus are designated a - g which points have

SUBSTIT been marked in Figure 6 which shows the controlling circuit more in detail.

From point 95 between the diodes 8a, 8b and the tyristor 9 th drive voltage is delivered to the controlling circuit C over a fuse 96. The drive_ voltage is supplied to the main conduit 97 of the controlling circuit over a diode 98 and a resistance 99 and is furthe supplied to a stabilizing circuit 100 providing the voltage stabilizin circuit marked with E in Figure 1. A voltage capacitor 101 connect between the return conduit 83 and the input of the stabilizing cir¬ cuit 100 smooths the rough rectified voltage. From a point 102 at the input of the diode 98 voltage is over a resistance 103 supplied to the base of a transistor 104 the emitter 105 of which is connec¬ ted to the return conduit 83.

When the voltage is higher than 0 V current is supplied from point 106 of the main conduit 97 through a resistance 107 to the co lector 108 of the transistor 104 and by the transistor to the retur conduit 103. When the voltage at the point 102 of the main conduit is merely zero the transistor 104 is- not conducting, and current is thereby supplied from point 106 of the main conduit 97 over the resistance 107 to the base of a transistor 109 which with the emit¬ ter is connected to the return conduit 83. The collector of the transistor 109 is connected to a synchronizing circuit 110 which- is an IC-circuit, for instance a circuit of the type "Signetics NE 555" A resistance 111 foresees that no signal enters the IC-circuit 110 when the transistor 109 is non-conducting. -The IC-circuit 110 start a delay time cycle which defines the time of the pulse when the re¬ charging starts. The length of the delay time is controlled by means of a capacitor 112 from the input current at point 113. The capacitor 112 is connected to the IC-circuit 110 at terminal VI thereof. When the capacitor 112 is charged to the reference vol¬ tage of the IC-circuit the said circuit emits a signal at terminal VII, which signal over the resistance 114 makes a transistor 115 conducting. A resistance 116 -foresees that the transistor is not mad conducting when there is no signal from the IC-circuit 110. The tran¬ sistor 115 amplifies the signal from the IC-circuit 110 and makes in turn transistor 117 conducting. The resistance 119 foresees that the transistor 117 is kept currentless in its non-conducting state. A

err

SUBSTITUTE SHEET A voltage is supplied to the collector of the transistor 117 by char¬ ging a capacitor 121 over, a resistance 118. When the transistor 117 is made conducting the voltage of capacitor 121 goes through the transistor 117 into a transformer 122. On the secondary side the transformer thereby supplies a trigging pulse over the terminals d and e of the controlling circuit to the tyristor 9 which is thereby ignited and supplies the recharging current to the battery 13. In the inactive state of the transistor 117 a resistance 120 connected parallelly over the primary side of the transformer 122 foresees that no voltage variations or sounds appear in the transformer depending on the transformer inductance. A variable resistance 123 connected between the main conduit 97 and the transistor 115 supplies a predetermined base charging current to capacitor 112. The transistor 115 gets its main current for making transistor 117 conducting from the capacitor 112 when charged.

The controlling circuit comprises an amplifier unit which is shown in the lower half of Figure 6. To the said amplifier unit the battery voltage enters from the outer .terminal c of the control cir¬ cuit. Over a resistance 124 the voltage is supplied to the minus terminal of an operation amplifier 125 in the form of an IC-circuit. The said input signal is inverted by the operation amplifier 125 and is amplified by a value which is determined by a resistance 126. The plus terminal of the operation amplifier 125 is supplied- with a fixed voltage the value of which is determined by the resistance di¬ viding circuit 127,128. The output voltage from the operation amplifier 125 goes through a fixed resistance 129 and a variable re¬ sistance 130 and provides a charging of the capacitor 112 from point 113. The charging of the capacitor 112 follows at different speed depending on the input voltage at the operation amplifier 125. A high battery voltage and thereby a high input voltage of the opera¬ tion amplifier 125 gives a slow charging of capacitor 112 and a low recharging current for the battery. The variable resistance 130 is formed as a voltage dividing circuit together with a fixed resis¬ tance 132 and supplies a voltage to a second operation amplifier 133. The said input voltage is compared with a reference voltage provided by a resistance dividing circuit 139, 140 which is connected to the negative terminal of the second operation amplifier 133. When the voltage over the variable resistance 131 connected parallelly over

the fixed resistance 129 is less than the voltage between the resis¬ tances in the resistance . divider 139, 140 the operation amplifier 130 is activated and a current is supplied through a resistance 134 to a transistor 135 which amplifies and transmits the current over the input terminal f of the controlling circuit C to the relay 94a which in turn switches over the switches 94b of the transformer to a higher voltage. At the same time the transistor 135 supplies a current over the diode 136 and the variable resistance 137 to a . point 138 between the fixed resistance 129 and the variable resistance 130. Thereby the resulting charge current for the capacitor 112 be¬ comes^' lower what means that the charging time for the capacitor 112 is made longer and that the recharging pulses to the battery are made shorter.

8y the above described switching over the mains transformer 3' between two different voltage levels the effect is obtained that the recharging of the battery follows with different characteristics. This is diagrammatically illustrated in Figure 7 in which five re¬ charging pulses are illustrated. In the two first pulses the re¬ charging is made by a character which is similar to direct current re¬ charging in that the trigging point 75 at which the recharging is started is located relatively close to 0 -. and thereby relatively long recharging periods 77 and corresponding short discharging periods 76 are obtained. Following the recharging of the accumulator battery the counter-EMF of the accumulator increases., and at the same time also the tendency of the accumulator to develop hydrogene gas is in¬ creased. As previously mentioned this involves serious disadvan¬ tages and restricts the recharging capacity of the accumulator. For eliminating such disadvantages the charging is switched over, as mentioned above, to a more accentuated alternating current rechar¬ ging in that the voltage of the transformer is increased. The vol¬ tage curve consequently becomes higher, and at the same time the trigging point 75' when the recharging is started is moved by the influence of the current going through the diode 136 and the variable resistance 137 which actuates the charging of the capacitor 112. By moving the trigging point 75' a substantial distance and prefer¬ ably to a point adjacent the 180° point shor.t recharging periods 77' and correspondingly long discharging periods 76' are obtained. For time reasons no hydrogene gas can be developed at such recharging and the accumulator is charged practically completely without hydro¬ gene gas development and to a substantially higher charge level than is possible by means of conventional direct current charging apparatus.

For making an external controlling possible of the control circuit the output terminal g of the control circuit is connected to a point 113 at the capacitor 112 and the corresponding second control conduit is connected to the return conduit 83.

It is to be understood that the above specification and the embodiments of the invention illustrated in the drawings are only illuminating examples within the scope of the inventional idea and that different kinds of modofications may be presented within the scope of the appended claims.

SUB

Claims

1-. Apparatus for recharging of dry batteries or accumulator batteries by means of pulsating current, preferably alternating current, comprising a mains con¬ nection circuit (A) and a recharging circuit connected to the mains circuit (A) and having terminals for one or more batteries (13) to be recharged, c h a r a¬ c t e r i z e d in that the recharging circuit (B) comprises a [rectifying means (8; 8a, 8b) which gives a direct current to a controllable current directing means (9) which am lifies and supplies a recharging current to the batteries during. a predetermined portion of the alternating current pulse and which is controlled to become conducted at a predetermined moment by a control circuit (C), and in tha't the apparatus comprises means (18; 84) allowing a slight discharging during the pe¬ riods (76, 78) appearing between the recharging pulse periods ⁽,71) .

2. Apparatus according to claim 1, c h a r a c¬ t e r i z e d in that the current directing means is a tyristor (9) which with the anode is connected to the mains circuit (A) and with the cathode to one pole ter¬ minal (12) of the battery or accumulator (13) to be re¬ charged, and which with the gate (39) is connected to the control circuit (C) which defines the time of the pulse (74) when the tyristor is made conductive.

3. Apparatus according to claim 1 or 2, c h a¬ r a c t e r i z e d in that the control circuit (C) comprises means (30-34; 130-137) for successively or stepwise moving the trigging point (75) of the alterna¬ ting current period when the apparatus starts supplying a recharging current to the battery (13).

4. Apparatus according to claim 1, 2 or 3, c h a r a c t e r i z e d in that the time controlling means is a PUT-transistor (29), a trig condensator (36) connected over the anode and the cathode of the PUT- transistor (29), a trimming circuit (33, 34) connected over the gate and the cathode of the PUT-transistor (29) and a second trimming circuit (30-34) connected over the gate and the. anode of the transistor (29) which trimming circuit (30-32) enables a controlling of the point (75) at which the PUT-transistor (29) ignites the tyristor ( 9) .

5. Apparatus according to claim 4, c h a r a c¬ t e r i z e d in that the second trimming circuit comp¬ rises a variable main resistance (31) which is the main control means by which the ignition point of the tyris¬ tor (9) can be controlled and which defines the length of the recharging period and thereby the intensity of the recharging current.

6. Apparatus according to any of claims 3, 4 or 5, c h a r a c t e r i z e d in that the control cir¬ cuit (9) comprises a diode (40) for preventing the appearance of a reverse current at the gate (39) of the tyristor (9).

7. Apparatus according to any of the preceding claims, c h a r a c t e r i z e d in that it comp¬ rises a switching in relay (45) and a switch between the tyristor (9) and one pole terminal (12) of the battery (13) to be charged which switch (21) is open at non- actuated relay (45), and in that the switching in relay (45) for starting the recharging is adapted to be ac¬ tuated either by a rest charge of the battery (13) or by a secondary circuit (F) from the mains circuit (A), and in that the apparatus comprises a disconnection relay (67) and a switch (41) connected in the conduit between the control circuit (C) and the tyristor (9) which switch (41) opens and brakes the control pulses to the tyristor (9), whereby the recharging of the bat¬ tery ceases.

SUBSTI 16

8. Apparatus according to claim 1 or 2, c h a¬ r a c t e r i z e d in that the mains connection cir¬ cuit (A) comprises a transformer (3) the secondary side of which has two outputs of different voltage level and in that the control circuit (C) comprises means (136, 137, 94a, 94b) for sensing the counter EMF of the bat¬ tery and which when the battery has reached a prede¬ termined counter EMF provides a continuous or stepwise increase of the voltage of the recharging current and concurrently therewith a delay of the ignition moment (75') of the tyristor so that the recharging is made by an increased voltage and a reduced recharging pulse period.

^'9. Apparatus according to claim 8, c h a r a c¬ t e r i z e d in that the components of the apparatus are designed for starting the recharging with relatively long recharging pulse periods and intermediate short discharging periods, and in that the means for rechar- - ging the pulse period comprises a relay (94a) which is adapted to be actuated from the control circuit (C) when the counter EMF of the battery increases a predetermined value and which thereby actuates a switch on the secon¬ dary side of the transformer (3) which connects a higher secondary voltage.

10. Apparatus according to claims 8 and 9, c h a r a c t e r i z e d in that the means for re¬ ducing the length of the recharging pulse period is a circuit (133) intended to compare the counter EMF of the battery with the nominal recharging volt-age and when a specific counter EMF is reached to reduce the charge voltage over a capacitor (112) the charge period of which defines the length of the discharging periods of the current pulses for the battery, whereby the said discharging periods (66* ) are made longer and the re¬ charging pulse periods (77) are made correspondingly shorter.