GB2242794A

GB2242794A - Apparatus for charging two batteries according to a priority sequence

Info

Publication number: GB2242794A
Application number: GB9007684A
Authority: GB
Inventors: Ian Ashworth
Original assignee: Technophone Ltd
Current assignee: Nokia Mobile Phones UK Ltd
Priority date: 1990-04-05
Filing date: 1990-04-05
Publication date: 1991-10-09
Anticipated expiration: 2010-04-05
Also published as: GB9007684D0; GB2242794B

Abstract

Apparatus for charging a main NiCd battery B1 in a portable electronic apparatus, specifically a cellular radio telephone 1, and also a spare NiCd battery B2 first fast charges battery B1 until a predetermined charge state is reached, whereafter battery B2 is fast charged until it reaches the predetermined charge state. Battery B1 is then trickle charged until the telephone 1 is removed from the apparatus, whereupon battery B2 is trickle charged. The apparatus may have a base unit 5 into which the telephone 1 and battery B2 can be plugged, and a charging current supply 15 separably coupled to base 5 by connectors 29, 30 so that the supply 15 can also be used on its own. <IMAGE>

Description

BATTERY CHARGING APPARATUS This invention relates to apparatus for charging batteries.

Nowadays, rechargeable batteries,. e.g. comprising NiCd cells1 are commonplace for powering a large variety of portable electronic apparatus.

By way of example, rechargeable batteries can be used in hand-held cellular radio telephones, so that the subscriber equipment is truly portable. However, particularly because of their transmission capability, portable cellular telephones consume a significant amount of power, necessitating relatively frequent recharging of the batteries. Also, it will often be advantageous for the user to have two batteries, one in use on the telephone and a spare.

In this case it is desirable to be able to charge both batteries rapidly using the same charging apparatus without having to disconnect or interchange the batteries during the charging process.

According to the present invention there is provided battery charging apparatus, comprising a first unit adapted to have two batteries removably connected thereto, and a second unit comprising means for supplying a charging current to the first unit, wherein the first unit comprises means conditioned to selectively connect the batteries to the current supply means in accordance with a predetermined priority sequence.

Battery charging apparatus in accordance with the invention allows two batteries in tandem to be charged rapidly and fully automatically in accordance with the predetermined priority sequence.

Furthermore, because the first and second units are separate, the present apparatus has the advantage that the second unit can also be used independently of the first unit for charging a single battery. To this end the second unit may be removably connected to the first unit.

In a preferred embodiment the current supply means are selectably operable in two different modes namely a rapid charging mode and a slower (trickle) charging mode. In this case the first unit comprises means for generating a control signal indicative of the required charging mode, and the current supply means responds to the control signal to provide the appropriate charge rate.

The predetermined priority sequence preferable involves the following steps in the order stated: a) supplying a rapid charging current to a first one of the batteries, b) supplying a rapid charging current to the second one of the batteries, and c) supplying a trickle charging current to said first battery.

Means may be provided in the first unit for sensing the charge state of the two batteries. In this case step (b) is commenced when the sensing means determines that the charge state of the first battery exceeds a predetermined level, and step (c) is commenced when the sensing means determines that the charge state of the second battery exceeds a predetermined level.

Furthermore, it may be arranged that the steps (a) and (c) are by-passed in the absence of a first battery1 while step (b) may be by-passed in the absence of a second battery. Additionally, slow trickle charging of the second battery may be initiated if the first battery is disconnected during step (c).

Suitably the first unit is adapted physically to hold the two batteries, e.g. in side-by-side relationship.

Preferably, the first unit is capable of holding a complete portable electronic apparatus, specifically a hand-held radio telephone, including one of the two batteries. The first unit may be arranged as a desk stand in which the telephone is held in an upstanding attitude so that it can easily be removed.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram illustrating a battery charging apparatus in accordance with the present invention for charging a battery in a portable cellular telephone in tandem with a spare battery.

Figure 2 is a perspective view of a desk stand unit forming part of the apparatus in Figure 1, showing a cellular telephone and a spare battery, Figure 3 is a plan view from below of the telephone in Figure 2, Figure 4 is a perspective view of the desk stand in Figure 2 showing the spare battery separated therefrom, and Figure 5 is a flow chart of the charging sequence in accordance with the invention.

The charging apparatus shown in Figures 1, 2 and 4 is intended for charging a first rechargeable battery pack B1 included in a portable cellular telephone 1, and a second, spare, rechargeable battery pack B2. The two battery packs B1 and B2 are essentially identical and may, for example, each contain six series connected NiCd cells each having a nominal voltage of 1.2V. The battery packs, therefore, each have a nominal voltage of 7.2V. The capacity of the individual cells is typically 700mAh.

The telephone 1 includes a transceiver and all the other circuits and features conventionally found in a cellular telephone, but which for the sake of clarity are not shown in the Figures. Also, since these aspects of the telephone are not relevant to the instant invention no further details will be given here, except to say that the circuitry in the telephone 1 is powered by the battery B1. The positive and negative terminals la, 2a and ib, 2b of the batteries B1 and B2 are connected to the positive and negative terminals 3a, 4a and 3b, 4b respectively of a desk stand unit 5.

Referring to Figure 2, the deskstand 5 comprises an upstanding block 6 having a substantially u-shaped recess in the form of an open-fronted pocket, receiving the lower portion of the telephone 1 so that the telephone 1 is held in a generally upstanding altitude.

In Figure 2 the telephone is shown with a greater angle of perspective that the desk stand simply in order that the battery pack B1 at the back of the telephone can be seen more clearly. As shown, the telephone would therefore have to be twisted slightly about its axis towards the reader as indicated by the arrow before it can be located in the pocket 7.

As shown in Figures 2 and 3, the terminals la, lb and 3a, 3b are provided in complementary connectors (40, 3) on the underside of the telephone (see Figure 3) and on the base of the desk stand 5 within the pocket 7 (see Figure 2). The terminals la, lb on the telephone and the terminals 3a, 3b on the base of the desk stand 5 are arranged to engage when the telephone is fully inserted into pocket 7. To this end the terminals 3a, 3b may be in the form of protruding pin-like connectors and the terminals la, lb may be in the form of female connectors.

As shown in Figure 2, a spare battery pack B2 can also be accommodated on the desk stand 5 next to the telephone pocket 7. This portion of the desk stand 5 comprises a generally flat platform 8 having two lateral rails 9 having recesses 10 for receiving complementary flanges 11 on the side walls of the battery B2. The desk stand 5 also comprises an upstanding back stop wall 12 having a central lip 13.

The battery pack B2 can thus be slidably inserted onto the desk stand 5 in the direction of the arrow until the leading edge of the battery pack abuts the back wall 12 of the desk stand at which point the pin-like terminals 4a, 4b in the back wall fo the desk stand engage complementary socket like terminals 3a, 3b (not shown) in the adjacent (leading) wall of the battery pack B2. Also the central lip 13 locates in a complementary recess 14 in the top face of the battery pack B2.

Returning to Figure 1, the battery charging apparatus also comprises a charger unit 15 having its own separate housing unit and connected to the desk unit by a three-core kink-resistant cable 16. The cable 16 comprises a positive and negative current carrying wire 17 and 18 respectively and a control line 19, the function of which will be described in more detail below.

The charger 3, which may be connected to a 220/240V AC mains supply 20, comprises a trickle charge circuit 21 for delivering a relatively low direct current, suitably of approximately lOOmA. This current is supplied to the external conductors 17 and 18 of cable 16 via internal conductors 22 and 23 respectively. The charger 15 also includes a fast charge circuit 24 capable of delivering a substantially higher direct current, suitably of approximately 700mA. This current is supplied to the external conductors 17 and 18 of cable 16 via internal conductors 25 and 26 respectively. A switch 27 enables either the trickle charge circuit 21 or the fast charge circuit 24. The switch 27 operates in response to a control voltage V applied thereto on conductor 28 connected to the control line 19 of cable 16.The switch is arranged to enable the trickle charge circuit 21 when a low control voltage, e.g. OV is applied on conductor 28, and to enable the fast charge circuit 24 when a high control voltage, e.g. +5V, appears on conductor 28. As shown, a low voltage is applied on conductor 28 and therefore the trickle charge circuit is enabled.

The cable 16 of the charger 15 terminates in a three-pin plug 29, the three pins thereof being connected to the respective conductors 17, 18 and 19.

The plug 17 is connected into a complementary socket 30 provided at a convenient location on a wall, e.g. a side wall, of the desk stand 5. The socket terminals 30a and 30b coupled to the positive and negative conductors 17 and 18 are connected internally to the positive and negative terminals 31 and 32 respectively of a voltage controlled switch 33. The socket terminal 30c is connected to a control voltage generator 34.

The control voltage generator 34 is capable of applying a voltage of OV or 5V to terminal 18c of desk stand connector 30 and hence to the control line 19 under the control of a microprocessor 35 to which the control voltage generator 34 is coupled.

The desk stand 5 also comprises a voltage sensor 36 connected across the terminals 3a and 3b of battery B1 and across the terminals 4a and 4b of battery B2 for monitoring the charge state of the respective batteries. The voltage sensor 36 is also coupled to the microprocessor 35.

The switch 33 in the desk stand 5 operates in response to a control voltage vc2 applied thereto from a further control voltage generator 39. For example, the switch 33 is arranged to connect battery B1 to the charger unit 15 when the control voltage Vc2 is low (e.g. OV), as shown but to disconnect the battery B1 and connect spare battery B2 when the control voltage Vc2 is high (e.g. +5V).

Additionally, a pair of lamp indicators, 37, 38 (suitably LEDs) may be included on the desk stand adjacent the respective battery B1 and B2 locations, (see also Figure 4) and the appropriate lamp is energized when the associated battery is being charged as a visual indicator to the user.

The sequence of charging the two battery packs is prioritised and fully automated under the control of the microprocessor 35. The priority sequence will now be described with reference to the flow chart shown in Figure 5.

Firstly, if the main battery B1 is connected, i.e. the telephone 1 together with its battery are correctly located in the pocket 7 of the deskstand 5, the voltage sensor 36 monitors the charge state of the battery B1.

If the sensed charge state is below a threshold value, e.g. 80% of the maximum charge capacity, the control voltage generator 37 generates a control signal Vc2 (e.g. OV) under the control of the microprocessor 35 which causes the voltage controlled switch 33 to connect the battery B1. Also, the microprocessor 35 causes the control voltage Vcl from voltage generator 34 to be high, e.g. +5V. The signal Vcl is applied on conductor 28 to switch 27 within the charge unit, which enables the fast charge circuit 24. Hence the battery B1 is subject to a rapid charging phase, An LED 37 connected across the terminals 3a, 3b is illuminated to indicate that charging of battery B1 is taking place.

Rapid charging continues until the charge state of the battery B1, as sensed by the voltage sensor 36, attains the predetermined threshold value, e.g. 80% fully charged. At this point the microprocessor 35 causes the control voltage Vc2 generated by the control voltage generator 39 to change (e.g. to +5V) in such manner that the switch 33 disconnects the main battery B1 and instead connects the spare battery B2 to the charger unit 15. However, the microprocessor causes the voltage generator 34 to maintain a high signal output, e.g. of +5 V, so that the fast charge circuit 24 of the charging unit 15 remains enabled. Hence, the battery B2 is now subjected to a rapid charging phase.

An LED 38 connected across the terminals 4a, 4b is energised to indicate that charging of the battery B2 is taking place. Rapid charging of the spare battery B2 continues until the charge state thereof, as sensed by the voltage sensor 39, attains the predetermined threshold value, e.g. 80% fully charged. At this point the microprocessor 35 causes the control voltage Vc2 from voltage generator 39, to change back to its former level (e.g. OV) so that the switch 33 disconnects the spare battery B2 and reconnects the main battery B1 to the charging unit. Also, the microprocessor causes the control voltage Vcl from voltage generator to go low, e.g. OV, whereby the fast charge circuit 24 is disabled by switch 27 within the charging unit, and the trickle charge circuit 21 is enabled instead. The main battery B1 is thus subject to a continuous trickle charge phase. Again charging of the battery B1 is indicated by the illumination of the associated LED 37.

If the telephone 1 (and hence the main battery B1) is removed from the desk stand 5, in which case the voltage sensor detects an open circuit, the microprocessor 35 responds by causing the control signal Vc2 from control voltage generator 39 to change to the value (e.g. +5V) which causes the voltage controlled switch 33 to reconnect the spare battery B2 in favour of the main battery B1. The control voltage Vcl from control voltage generator 34 is unaltered, i.e. remains low, so that the trickle charge circuit 21 remains connected. Hence the spare battery B2 is now subject to a continuous trickle charge phase. As before, charging of the spare battery B2 is indicated by the illumination of the associated LED 38.

Trickle charging of the spare battery pack B2 may continue ad infinitum unless and until the spare battery is removed, in which case the charger unit may be disabled, e.g. by appropriate activation of switch 27 to a neutral position, by the application of an appropriate control voltage Vcl from generator 34 under control of microprocessor 35.

If during the charging sequence either a main battery B1 or a spare battery B2 is connected or reconnected the operating sequence is interrupted and the whole charging sequence begins again from the start, as shown in the flowchart of Figure 5.

On the other hand if the desk stand 5 is used for charging a spare battery B2 alone the voltage sensor 36 will detect an open circuit when the switch 33 attempts to connect the main battery. In this case the microprocessor 35 responds by omitting the charging steps relating to the main battery (i.e. the battery connected to terminals (3a, 3b).

Likewise, in the hence of a spare battery B2, the voltage sensor 36 will detct an open circuit when the switch 33 attempts to connect the spare battery and the microprocessor 35 responds by omitting the charging steps relating to the spare battery. Hence the desk stand can also be used for charging a main battery alone.

Since the charging apparatus in accordance with the present invention comprises a discrete charging unit, it is possible to disconnect the cable 19 from the deskstand 5 and to re-connect it directly to the telephone or via a suitable adaptor (not shown) to a spare battery pack, thus permitting the telephone or battery to be charged directly from the charging unit 15 if it is not required to charge two batteries together.

In this case the telephone itself may be provided with means for generating a control signal Vcl enabling selection of either the fast or trickle charge modes in accordance with our co-pending British patent

application No. L (Our Ref: PAT 90005).

In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. For example, rather that employing two distinct circuits 21 and 24 for slow and fast charging as depicted herein, a common circuit may be employed wherein the current output is varied in accordance with the control voltage Vcl.

Moreover, instead of using a constant low current, the trickle charge mode may be effected by pulsing a higher current. Thus, for example, a 700 mA source may be pulsed on for O.lt and off for 0.9t (where t is the period of the pulse) in order to achieve a trickle charge effect similar to the 100 mA constant source mentioned above.

Claims

1. Battery charging apparatus, comprising a first unit adapted to have two batteries removably connected thereto, and a second unit comprising means for supplying a charging current to the first unit, wherein the first unit comprises means conditioned to selectively connect the batteries to the current supply means in accordance with a predetermined priority sequence.

2. Battery charging apparatus as claimed in claim 1, wherein the second unit is removably connected to the first unit.

3. Battery charging apparatus as claimed in either of the preceding claims, wherein the current supply means are selectably operable in two different modes, and the first unit comprises means for generating a control signal, the current supply means being responsive to said control signal to operate in a mode in accordance with said control signal.

4. Battery charging apparatus as claimed in claim 3, wherein a first charging mode involves supplying a rapid charging current, and a second charging mode involves supplying a trickle charging current.

5. Battery charging apparatus as claimed in any of the preceding claims, wherein the predetermined priority sequence, involves in the following order, the steps of a) supplying a rapid charging current to a first one of the batteries, b) supplying a rapid charging current to the second one of the batteries, and c) supplying a trickle charging current to said first battery.

6. Battery charging apparatus as claimed in claim 5, wherein the first unit includes means for sensing the charge state of the two batteries, wherein step (b) is commenced in response to the charge state of the first battery exceeding a pre-determined level, and step (c) is commenced in response to the charge state of the second battery exceeding a pre-determined level.

7. Battery charging apparatus as claimed in claim 5 and 6, wherein the first unit includes means for sensing the presence of the two batteries, and means responsive to said battery presence sensing means for omitting steps (a) and (c) in the absence of the first battery and omitting step (b) in the absence of the second battery.

8. Battery charging apparatus as claimed in claim 7, including means responsive to the battery presence sensing means conditioned to supply a trickle charge current to the second battery when the first battery is disconnected during step (c).

9. Battery charging appa us as claimed in any of the preceding claims wherein the first unit is adapted to hold the two batteries.

10. Battery charging apparatus as claimed in claim 9, wherein the first unit is adapted to hold the two batteries in side-by-side relationship.

11. Battery charging apparatus as claimed in claim 9 or claim 10, wherein the first unit is adapted to hold a portable electronic apparatus including one of the two batteries.

12. Battery charging apparatus as claimed in claim 11, wherein the portable electronic apparatus is a radio telephone.

13. Battery charging apparatus as claimed in claim 12, wherein the portable electronic apparatus is a cellular telephone.

14. Battery charging apparatus as claimed in claim 12 or claim 13 wherein the first unit is adapted to hold the telephone in an upstanding attitude.

15. Battery charging apparatus for charging two batteries in accordance with a pre-determined priority sequence substantially as herein described with reference to and illustrated in Figures 1 to 5 of the accompanying drawings.