Battery charger for two cell holding modules

CLAIM FOR THE PRIORITY of the patent application / utility model

IN THE UNITED STATES OF AMERICA

March 25, 1980

Brief Description filed in support of a request for

PATENT OF INVENTION

Luxembourg on behalf of: GENERAL ELECTRIC COMPANY for:

Battery charger.

The present invention relates to small and economical battery chargers offering excellent charging performance for consumer sized batteries and greater flexibility than known chargers.

The invention constitutes an improvement in. Accumulator charging systems of the type described in US Pat. No. 4,009,429. A charging system of this type is marketed by the General Electric Company, and it allows accumulators of various sizes to be charged. It comprises a battery charger which can be plugged into an electrical outlet and a battery holder module adapted to the charger, chosen from several of these modules, which holds and interconnects two or four accumulators.

The accumulator charging system envisaged above has met with great commercial success in the public. It is efficient, relatively economical and easy to use. The terminals of the battery charger and the structure of the battery holder modules are such that it is practically impossible to incorrectly associate the battery holder module and the battery charger. An important feature of this charger is that it can be plugged directly into an electrical outlet, so that the charger, when associated with the battery holder module, forms a self-contained unit which is supported by the outlet. eUe. This eliminates the need for extension cords or the like, and allows the user to leave the charger plugged into the outlet while the batteries are charging. In addition, the current of the charger is such that the accumulators can be left to charge constantly.

The existing battery charger which has just been described, however, has a limiting characteristic which consists in that it can only accept one type of battery holder module at a given time. Thus, if one wishes to immediately charge a pair of size C batteries that one needs while batteries of size AA, for example, are being charged, one must remove the size battery holder module from the charger. AA before charging is complete, to replace it with the size C battery module. Another limitation of the existing charger is that the charging current is limited to about 0.1C, denoting the capacity of the accumulator by C, in ampere-hours (Ah). Thus, for a typical size AA 10 accumulator having a nominal open-circuit voltage of 1.2 V and a capacity of 0.5 Ah, the charging rate C / 10 corresponds to a current of 50 mA. At this rate, the recommended charging time is 12-16 hours. It is desirable to increase the charge rate to about C / 6 or 0.15C in order to allow the batteries to reach a full charge in 8 to 12 hours.

However, a larger transformer is needed to achieve a higher load rating. This generally requires that the battery charger be able to withstand the higher mechanical stresses which are transmitted to the reed connectors which plug into the electrical outlet. '

The invention provides an improvement in the principles and advantages of the battery chargers and charging systems described in US Pat. No. 4,009,429, mentioned above. The battery charger of the invention is designed to combine with existing battery holder modules but, in addition, it provides a higher charging current and it has a configuration allowing to accept two battery holder modules simultaneously. , regardless of whether the accumulators to be charged have the same size or different sizes. Thus, according to the invention, it is possible to simultaneously charge batteries of size AA, C and D, 35 as well as 9 V batteries for special applications. In addition, the battery charger is designed so that when battery holder modules are associated with it, the system does not block access to the second element of a double electrical outlet. The invention makes it possible to achieve the above advantages, as well as others, thanks to an original association of its essential elements. The battery charger comprises a charger housing having two opposing sides, which are generally parallel, for mounting separate battery modules to be charged. First and second sets of external terminals are attached to these sides and these terminals are intended to be connected to associated terminals of the battery module, the terminals being designed to releasably support the module. A transformer located inside the housing has a magnetic circuit, a primary winding and two secondary windings wound on the magnet circuit. The secondary windings are respectively connected to the external terminals located on the opposite sides, in order to provide them with a load current. A pair of blade connectors are internally connected to the primary winding and extend from the side of the housing which is between the opposing sides. These connectors are spaced a certain distance apart in the direction of spacing between the opposite sides and they support the charger in the electrical outlet. In the preferred embodiment, a ground pin is used to help support the weight of the battery charger. This earth pin is mechanically coupled to the structure of the magnetic circuit of the transformer and passes through the housing so as to enter the earth contact of the socket.

The remainder of the description refers to the accompanying drawings which respectively represent:

Figure 1: a perspective view of a battery charger corresponding to the invention, shown with two types of battery holder modules which can be used with it;

Figure 2: a side elevational view of the battery charger;

Figure 3: a plan view of the charger;

Figure 4: a section along line 4-4 of Figure 3; '

Figure 5: an exploded representation of the components of the charger;

Figure 6: a detail section along the line

6-6 of Figure 5;

• Figure 7: a series of electrical diagrams of the battery charger and typical examples of battery holder modules that can be coupled to it.

Figure 1 shows that the battery charger of the invention comprises a housing 10, a pair of reed connectors 12, 13 and a ground pin 14. The connectors and the pin are received in the respective contacts of a socket. (not shown) when the charger is plugged into the outlet for use. These three connectors 12-14 not only have the function of transmitting electrical energy to the charger, but also of mechanically supporting the charger and the modules associated with it.

Housing 10 has two opposing sides 16, 18, which are generally parallel and having recessed surfaces 17 and 19. Sides 16, 18 and blades 12, 13 are spaced in the same direction so that when the charger is associated with two battery-holder modules and is plugged into a socket, it does not block access to the second element of a double socket. Connector blades 12, 13 and ground pin 14 start from inside the housing and pass through housing cover 20 which closes the open side of housing 10.

Two different types of representative battery holder modules are shown in Figure 1. On the left side of the charger is a module 22 having a capacity which allows it to accommodate four AA size batteries 23. On the right side of the charger is a 9V battery 24, associated with an adapter 25 which is shown unplugged. The battery holder module 22 is described in detail in the aforementioned US Patent 4,009,429 as well as in US Patent 4,173,733. The battery charging module 22, containing four AA size batteries, is a three terminal module which fits one of the sets of terminals located on the side of the charger. On the other hand, the battery adapter / holder 25 is a two terminal device which is designed to fit two of the three external terminals on either side of the charger. The external charging terminals are clearly visible in the drawings and are similar to the terminals on top of the prior art commercial charger 10 described above. However, here there are two separate sets of three outer terminals and these sets are located on opposite sides of the charger, namely one set 26, 27 and 28 on the recessed surface 17, and the other set 30, 31 and 32, on the recessed surface 19. The terminals 26-28, 30-32 are push button type terminals which releasably support the weight of the modules when the modules are attached to the charger by the push button type terminals. It will be noted that the external terminals placed on the sides of the charger are located asymmetrically with respect to the recessed surfaces 17, 19, so as to prevent any connection error of a battery holder module or of an adapter. The walls 17a, 19a which are formed in the side of the housing by the recessed surfaces 17, 19 participate in the terminal positioning function of the charger, as the wall prevents a module from being overturned and from being overturned. connect it with reverse polarity. In addition, there is a small T-shaped protrusion, 35, which is disposed between the terminals on each side of the battery charger. Its function is to assist in the orientation and disconnection of the module terminals with respect to the charger. Considering Figures 4 and 5, it can be seen that the interior of the housing 10 contains a load transformer 40 which comprises a magnetic circuit 41, a primary winding 43 wound on the magnetic circuit and two secondary windings 45, 46, also wound. on the magnetic circuit. The transformer lowers the mains voltage which is applied, the secondary windings.

providing low voltage alternating charging current (e.g. 10 V_eff) As is conventional, the primary and secondary windings of the transformer are wound around a mandrel 47 which is then placed around the central branch of the magnetic circuit 41, before adding the yoke 41a of the magnetic circuit to close the circuit . magnetic. In accordance with the invention, the windings of the transformer are chosen so as to provide the external terminals with a nominal load current of approximately 0.15C.

Still in accordance with the invention, the transformer is connected to these external terminals so that the corresponding external terminals located on the respective sides have opposite electrical polarities, for a purpose which will be explained shortly. The magnetic circuit structure of the transformer supports the blades 12, 13 which are mounted on insulating blocks 48, 49 which are part of the mandrel 47.

A metal U-profile, 51, surrounds the sheets 50 (shown separately) of the magnetic circuit, clamping these sheets against each other and forms an integral part of the magnetic circuit. This structure is shown in detail in Fig. 6, which is a partially sectional representation taken along line 6-6 of Fig. 5. As shown, the U-profile 51 also functions as a mounting plate for the earth pin. 40. For this purpose, it has a slightly protruding part 51a near the place where the pin 14 is coupled to it.

A particular feature of the invention is the ability of the charger to receive one or two externally connected modules, without any auxiliary mechanical support. Because the transformer and the housing containing the outer terminals form a unitary mechanical structure, all forces which are applied to the housing are also transmitted to the transformer. It can therefore be seen that the torque and the forces of gravity resulting from the fixing of an external module on a set of external terminals, or on both, are transmitted by the housing 10 to the transformer, and therefore to the blade connectors 12, 13 and ground pin 14. In order to reduce the torque that would be applied to the connectors by connecting to the charger a single module or modules of different weight, thus creating a mechanical imbalance, the case, the 5 windings and the magnetic circuit of the transformer are all narrower in the dimension corresponding to the distance between the two module receiving faces.

Thus, the cross section of the magnetic circuit 41 of the transformer is narrower in the direction corresponding to the spacing between the two module receiving faces than in the direction corresponding to the spacing between the other two sides of the housing. In a preferred embodiment, the section of the magnetic circuit measures 6.3 mm X 9.5 mm. In addition, the ground pin 14 contributes to the torque resistance as it is rigidly mechanically coupled to the metal channel 51 of the magnetic circuit of the transformer.

By considering figures 4 and 5, we see that the terminals T. - T_vs of the transformer are fixed to the mandrel 20 of the magnetic circuit so as to be connected by conductive wires 55 to appropriate terminals among the terminals 26-28, 30-32. In practice, these conductors 55 are first of all fixed to the internal part of the external terminals and they are then soldered to the transformer terminals.

- Τθ, before the installation of the transformer in the housing 10. The housing 10 is then closed by fitting the cover 20 which has cutouts intended to receive the blade connectors 12, 13 and the earth pin 14. The cover 20 is attached to housing 10 by any suitable attachment method, such as, for example, ultrasonic welding.

Figure 7 shows the electrical circuits that can be associated with the charger, which is shown on the left side of the figure. As previously indicated, the primary winding 43 is connected to the connectors 12, 13 so as to be connected to the mains voltage source E. The respective terminals T₁ - Τθ and - Τ $ of the secondary windings 45, 46 are connected to the external terminals s

respectively 26 - 28 and 30 - 32, as has also been explained previously. The three figures placed to the right of the transformer schematically represent three types of receiver circuits A, B and C that the charger may encounter during its use.

Receiver circuit A represents the electrical diagram corresponding to accumulator charging modules 22 of the type shown in FIG. 1, each of them containing two or four accumulators. When two such modules are connected to the charger, up to eight AA size batteries can be charged simultaneously. These modules contain internal circuits intended to interconnect the accumulators and to rectify the applied current. The rectification is effected by the diodes 60, 61 which are connected in series with the accumulators. These diodes also prevent an accidental discharge of the accumulators in the event of an accidental short-circuiting of any terminals among the terminals A ^ - Αθ or A₄ - Αθ. It will be noted that when the primary winding of the battery charger 20 is connected to an external source E, and in the hypothesis where two modules with four accumulators 22 are attached to the charger, a charging current I_could simultaneously circulates in the accumulators which are connected between the terminals A ^ and A₂ and in the two accumulators which are connected between terminals A_& and Αθ of the second modulus. This results from the fact that the secondary windings of the transformer have polarities such that the corresponding external terminals are in phase opposition from the electrical point of view. When the charger is connected to receiving circuits such as circuit A, this opposite electrical polarity is of no significant importance, as each secondary winding does not distribute more than half of the maximum total charge current over the course of n any half-cycle, regardless of the number of accumulators in the modules 22. More precisely, because the diodes 60, 61 are connected so as to conduct alternately, the charge current is never applied to more than four accumulators during any half cycle of the mains current.

Circuit B represents the type of receiver circuit that the charger encounters when two size C accumulators or two size D accumulators, 64, 5 are connected to the charger in a two accumulator module 63, which includes a rectifier diode 65. charger • here is sensitive to the flow of the charging current. If the secondary windings of the charger had the wrong electrical polarity, it would be possible for the charger to supply the maximum total charge current for only half a cycle of the input wave and not to supply any charge current during the other. half cycle of the wave. This condition would subject the charger to very poor voltage and current regulation and would require to some extent that the transformer be designed to accept a higher primary current than necessary. For this reason, the corresponding external charger terminals, 26, 30, have polarities such that they are in phase opposition, while the terminals 26 and 32 are in phase. Thus, when terminal 26 is at maximum positive amplitude, terminal 32 is also at maximum positive amplitude and terminals 28 and 30 are at minimum negative amplitude. Under these conditions, when circuit B type receiver circuits are connected, the respective modules receive current in separate half cycles of the input wave. The same situation exists in the case of the load of receiving circuits such as circuit C. This is the type of receiver circuit found in the case of adapter / battery combinations, such as that shown in Figure 1 by battery 24 and adapter 25. Here again, the adapter includes diode 66 as well as A current limiting resistor 67, for the purpose of protecting against excessive charge current the generally smaller accumulators which make up the battery.

The table below indicates the load current which is supplied for the minimum and maximum values ​​of the mains voltage which is applied, for the various types of receiver circuits shown, assuming that two modules are connected to the transformer.

CIRCUIT A (2, 4, 6 or 8 accumulators of 500 mA.h each) ^EEB ^ICH (VAr) (Vz) (mA)

104 2.9 50 (minimum)

127 2.9 100 (maximum)

CIRCUIT B (2 or 4 accumulators of 1.0 Ah each)

<td>E Ε_βW) (v =) 104 2.9</td><td>^ICH (mA) 110 (minimum)</td>

<td> 127 2,9</td><td>160 (maximum)</td>

CIRCUIT C (1 or 2 batteries of 65 mA.h each) ^EEB ^Σ0Η (VM (V-) (mA)

102 8.7 8 (minimum)

127 8.7 18 (maximum)

It can be seen that size AA batteries (circuit A) with a nominal capacity of 400 mA.h are charged at a nominal rate of 0.15C (75 mA) for a mains voltage E =. 115 V. Typical size C and D accumulators with a nominal capacity of 1.0 Ah are charged at a rate of approximately 0.14C (140 mA) when the mains voltage is 115 V. Batteries (circuit C) with a nominal capacity of 65 mA.h are charged at a rate of 0.2C when the mains voltage is 115 V. The battery charging current is limited in this case by the 56 ohm resistor which is plugged into the adapter charging circuit 25, and it could be increased by reducing the value of the resistor. The current absorbed depends on the electromotive force of the accumulator and its polarization voltage, as well as on the characteristics of the transformer. The charging current obtained by the invention is, however, significantly higher than that provided by the previous single module charger.

Choosing the phases of the secondary windings of the transformer so that the corresponding external terminals have opposite phases allows operation with higher load currents than would be obtained with in-phase secondary windings. For comparison, for a case of circuit B, a charger with secondary windings in phase produces charging currents with an average value of 95 mA to 117 mA.

Secondary windings in phase opposition produce load currents with an average value of 112 mA to 146 mA, or currents greater than 15% to 25%.

Although it is preferable to use two secondary windings, due to the better current regulation obtained when switching from the two accumulator configuration to the four accumulator configuration of circuit A, it is possible to '' use a single secondary winding without a tap when poorer load current regulation can be tolerated. In such a case, the end terminals of the secondary winding are connected to the corresponding external terminals on both sides of the charger, instead of being connected on only one side. If this is done, it is preferable to employ rectifier diodes between the secondary winding and the outer terminals so that the load current pulses which are applied to the respective sets of terminals appear in alternating lobes of the sinusoid. This improves current regulation by ensuring that a receiver circuit which is loaded and which is connected to one set of terminals does not conduct current at the same time as a receiver circuit which is connected to the other set of terminals. In other modified versions, the charger may include rectifying diodes mounted inside the housing, as for example in cases in which the battery holder module does not include any rectifying means. The diodes would be connected between one of the transformer terminals T ^, T $ or T ^, Τθ and the corresponding external terminal. It should also be noted that the rectifier could be connected so that it is compatible with certain battery-holder modules of the type shown in which diodes are incorporated.

It can be seen from the foregoing that the improved charger of the invention offers great flexibility by virtue of certain features which are not found in chargers of the prior art. More specifically, it allows several circuits or external accumulator modules to be connected and charged simultaneously and it allows several types and kinds of receiving circuits to be mixed which may require different charging currents. The charger is economical, compact, interesting and it can be used on a double electrical outlet leaving the second part of the outlet accessible to the user. In addition to the above, it allows accumulators to be charged at significantly faster speeds. This results from the ability to accommodate a larger transformer in a smaller footprint enclosure, while meeting the safety requirements of applying only limited mechanical stresses to the electrical outlet connectors.