MXPA00004035A - Method and circuit for controlling charging in a dual battery electrical system - Google Patents

Abstract

A control circuit for controlling the recharging of two batteries in a dual battery vehicle electrical system includes a charging circuit (20) for stepping up the voltage of a reserve battery (RES.), so that it can be applied to a starting battery (HPB), an alternative circuit path (18, 19) to allow charging of both batteries by the alternator (A) when the vehicle engine is running, and a controller (30) for switching the connection of the batteries through the charging circuit (20) and the alternative circuit path (18, 19) under various combinations of conditions.

Description

METHOD AND CIRCUIT FOR CONTROLLING THE LOAD IN A DOUBLE BATTERY ELECTRICAL SYSTEM TECHNICAL FIELD The present invention relates in general to electrical systems for motor vehicles and more particularly to a dual battery electrical system, for supplying electric power to the motor vehicle and for maintaining the charge of the dual battery system.

BACKGROUND OF THE INVENTION Typically, vehicles powered by internal combustion engines have an electric starter motor to start the engine. The starter motor is electrically connected to a starting circuit which receives the electrical energy coming from an electrical storage battery. When an ignition switch is operated, the energy from the battery is supplied to the starter to rotate the internal combustion engine. In common vehicle applications, the devices REF .: 119581 such as the engine controls the "electronic systems, lighting and vehicle accessories, which present an electric charge to the battery or the alternator, when the engine of the vehicle is running." Traditional batteries are often referred to as starter, lighting and ignition (SLI) batteries In design and construction, these are lead-acid, multi-cell batteries, which are constructed from lead plates that carry active material and are arranged in stacks or rows. batteries are inserted into compartments of a battery cell compartment, electrically connected, and flooded with dilute acid electrolyte.The start-up requires high energy input for a short period of time.The SLI batteries of this construction are more than adequate to provide the relatively high energy demand required to start the engine. the electric charges in the vehicle during the operation of the vehicle during periods of non-operation, contributes to a relatively lower energy demand than the start-up. The SLI battery design is difficult to optimize to operate, both in the high-power-short-duration power, and the long-lasting low-power-power. An additional drawback of the SLI batteries is the relatively low specific energy (kilowatt hours / grams (J? J / g)) compared to battery constructions due to the weight of the lead plates and the liquid electrolyte. energy for vehicle lian incorporated two batteries. A first battery in the system, a starter battery, is optimized for engine start-up, that is, designed specifically for high-power, short-lived power. A second battery in the system, a backup battery, is optimized to operate and maintain electrical charges not starting. An advantage of such a system is that the starting battery can be made smaller and lighter and still capable of providing high power power for a short period of time. In addition, the backup battery can be made smaller and lighter, and still be able to meet the relatively low power requirements of vehicle accessories. In combination, the two-battery system can be designed to take up less space and less weight than a traditional, simple SLI battery. Dual battery systems require control circuits to maintain the charge of both batteries in the system. Typically, the vehicle includes a regulating device that regulates the power of the alternator in response to the load needs of the SLI battery and the electric charges of the vehicle. In a dual battery system, each type of battery distributes energy and accepts charge at a different speed. For example, the starter battery distributes energy at a very high speed and likewise accepts load at a high speed. By contrast, the backup battery distributes energy at a lower speed and accepts load at a lower speed. Each battery will typically show a different state of charge and therefore requires different load maintenance. Additional advantages can also be achieved by selectively coupling or uncoupling the batteries during the non-operational start-up and operational periods of the vehicle. However, careful handling is required so as not to damage the vehicle's electrical system or the dual battery system. Therefore, a dual-battery battery is needed for vehicle start-up and operation that provides the advantages of reduced size and weight, and that includes energy and load management. Dougherty et al., U.S. Patent No. 5,162,164, discloses a dual battery system in which two hambers are contained in a single carrying case. In this way, it should be understood that the identification of the two batteries means, without limitation, containment either in separate cases or in a single case. United States Patent No. ,525,891 discloses a vehicle with a starter battery, a backup battery and a charge / separation module forming a charge circuit path that is connected from the backup battery to the starter battery. The charging circuit is connected and disconnected in response to the starting battery voltage, the reserve battery voltage, and the on / off status of the vehicle.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a control circuit for a dual energy storage system for a vehicle. While the invention is described in terms of two batteries, it also contemplates systems in which a starting battery is replaced with a starting capacitor. The term "charging power source" will be used to include batteries, capacitors and other types of equivalent charging power sources In various preferred embodiments of the present invention, electronic devices for controlling the battery, electronic control devices of the vehicle and combinations of these electronic control devices are used for the handling of the battery charge and improved system performance.For example, the system is adaptable to automatically determine the charging status of the batteries in the system and to couple , as appropriate, the battery or batteries with enough charge to operate essential vehicle electrical charges and provide power for starting.

In addition, a preferred load handling strategy reduces the potential for overloading one or more of the system's batteries, maintaining and still flushing each of the batteries in a ready-for-use state of charge. These and other advantages and objects of the invention will be appreciated from the following description, in the. which reference is made to the appended drawings, which are a part of the teaching of the invention, and in which a preferred embodiment of the invention is illustrated. The description and illustration of the preferred nodality is by way of example and not by way of limitation. For the various embodiments of the invention within the scope of the invention, reference is made to the claims which follow the description.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram illustration of a dual battery system adapted to an electrical system of a motor vehicle according to a preferred embodiment of the present invention; Figure 2 is a detailed schematic illustration of a dual battery system controller according to a preferred embodiment of the present invention; and Figure 3 is a detailed schematic diagram of a voltage elevation circuit observed in Figure 2.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY With reference to Figure 1, an electric vehicle system 10 includes a starter battery, also referred to as a high-energy battery (HPB). This refers to the short or instantaneous high lift of the energy that is necessary to start the vehicle. The starting battery HPB is connected through a pair of switch contacts 12 to an electric starter motor (S) 13. The starter motor 13 is mechanically coupled to the internal combustion engine (not shown) through an axle of departure (not shown), and when the starter motor 13 is rotated, it rotates the internal combustion engine to start combustion of the fuel in the presence of a spark.

The starting battery -HPB is preferably a battery of recent technology that provides the high starting energy, necessary in a smaller package or package than the traditional SLI batteries. Such a new type of starter battery is shown and described in co-pending US Patent Application No. 08 / 870,803, filed June 6, 1997, assigned to the assignee of the present invention and entitled "Battery of Modular Electrical Storage ", the description of which is expressly incorporated by reference herein. Such a starting battery should typically provide 800 amps of current at a starting voltage of 10 ... 0 volts for the start-up and have 4.5 amp-hours of reserve power capacity. The vehicle electrical system 10 also includes a backup battery (RES.) Which is preferably of the absorptive glass mesh (AGM) type construction having high reserve capacity. The backup battery RES. it is adapted to provide a relatively low speed discharge for a prolonged period of time. The backup battery can typically have a nominal capacity of twenty-three ampere-hours of energy storage capacity and a nominal capacity of twenty-five amperes at a nominal voltage of eleven volts. Next to the backup battery RES. there is a conventional alternator (A) 14 which is a type of electric generator driven by the internal combustion engine, to supply rectified DC power, to charge the batteries and to operate other loads in the vehicle. An ignition switch with two "ON" and "Start" switch positions is represented by the two ON and START switches with the corresponding labels in Figure 1. The RES reserve battery for vehicle is connected to a resistive load. 15 (the trunk light, for example), even when the ignition switch is open (the "off" position). The resistive load 16 represents the vehicle's loads when the ignition switch is operated to close the ON switch, which remains closed, during and after the start-up, the START-UP switch is closed during start-up, to supply the electrical energy from the alternator 14 through the resistor 17, and is then opened.The essential vehicle loads may include loads such as the vehicle engine / power train driver, the lighting-systems, the brake system controller, the driver of the safety system and if my l which are energized during the operation of the vehicle. Other vehicle charges may include entertainment system, convenience features and others that >; they are - essential or required for the operation of the vehicle. When the ignition switch is moved to the "Start" position (the "START" switch and the "OFF" switch are closed), an ignition coil Ll is energized to close the start contacts 12, and ia Power is supplied from the HPB starter battery to the starter motor 13. During the times when the vehicle's engine is off, and the times after the vehicle is started, you want to charge the HPB starter battery. is being operated, such recharging of the battery is provided by the alternator 14. When the vehicle is off, such recharging can now be provided by the backup battery RES.In order to control the voltage and charging speed of the battery starting circuit HPB, this is coupled through a charging circuit 20, including a voltage raising circuit 21 to be described later.The charging circuit 20 is electrically connected to the starting battery HPB through a relay 18 having a normally closed position iNC) and an open position (O) represented by the respective "NC" and "O" contacts. With the relay 18 in the normally closed condition, the charging circuit 20 is connected to one side of the starting battery HPB. In order to be operable, however, the charging circuit 20 must also be connected to 1 ^ reserve battery RES. to receive the energy, and the charging circuit 20 must be enabled by a signal on an ENABLE line that runs from an electronic controller 30. With the relay 18 energized, the charging circuit 20 is diverted through a alternative circuit path that includes an optional 19 PTC resistor (positive temperature coefficient). This PTC resistor 19 acts as a time-dependent fuse, and provides what is effectively an open circuit at certain thresholds of the current flowing through corresponding periods of time, and then readjusts after the current sufficiently decreases. A 9 amp poly switch available from Raychem is an example of a component suitable for use for this purpose. The controller 30 is also connected to the coil Rl of the relay to operate the relay 18. The controller 30 is also connected to detect the state of the switch in an input. The controller 30 is also connected through the diodes DI and D2 to receive power from the batteries HPB, RES. A power supply capacitor 22 is connected to the cathode of the diode DI in the circuit path, which arrives from the starting battery HPB. The controller 30 operates in accordance with a group of states or logical conditions, the logic and programming of which will be explained later herein. Referring now to Figure 2, the electrical system 10 of the vehicle is shown in further detail with respect to the charging circuit 20 and the electronic controller 30. A detailed scheme of the voltage rise circuit 21 is illustrated in Figure 3. backup battery. _RES. is connected through diode D3 to a regulator. voltage. 2.3 to provide a voltage supply of +5 volts to energize electronic devices in the circuitry -shown in the üignra 2. A switch 24 and drive resistors (not shown) are provided to provide a plurality of inputs to a circuit programmable array logic (PAL) _2-5 which provides the control logic for the complete circuit set shown in Figures 1 and 2, The PAL circuit is preferably an integrated circuit PALCE22V10Z-251P, available from VantAs., a Successor of -Advanced Micro Devices. A time base generator circuit 26 provides synchronization signals to the PAL circuit 25. The circuit 26 includes an integrated ICM 7555 synchronizer or templer circuit available from Harris Semiconductor. This circuit provides the synchronization signals, such as a train of pulses with a periodic waveform of 5 seconds that is counted by the PAL 25 circuit to synchronize the longer delay periods. The backup battery RES. it has its output connected to a splitter circuit 27 to scale the output to a nominal level of +2.5 volts. The splitter circuit 27 is provided by four pairs of two resistors in series, which forms a precision voltage divider with four determined proportions by the desired trigger point of the comparators 28. The comparators 28 are available TCL2252IP of amps or doubles. of Texas Instruments. The comparators 28 compare the output of the reserve battery RES. at the various thresholds including 12.2 volts DC, 13.1 volts DC and 13.4 volts DC, the significance of which is explained below. The outputs of the comparators 28 are connected to the inputs on the PAL circuit 25 to detect the voltage of the reserve battery RES. The starting battery HPB in Figure 2 is connected to the input of the HPB switch of the relay 18 observed in Figure 2. The normally closed terminal (NC) in Figure 2 is connected to a voltage trigger circuit 21, which is a more detailed embodiment of the charging circuit 20 in Figure 1. The voltage rise circuit 21 translates or converts the reserve battery voltage from its level to 13.1 - 13 ^ 4 volts to a level such as 14.0 volts , representing the fully charged condition of the HPB starter battery. The voltage of the starting battery is detected through the connection of the voltage rise circuit and through another group of comparators 29, which detect the thresholds such as 14.0 volts DC, 13.8 volts DC and 12.75 volts DC for the Xa .texl. Starting HPB, the significance of these thresholds is explained later. The same type of commercial circuits can be used for the comparators 29, as described above for the comparators 28. A second voltage divider circuit 33 is connected between the output of the voltage rise converter 21 and the inputs to the comparators 29 The voltage divider circuit 33 is formed of resistor pairs to scale the comparator trigger points to a nominal +2.5 volts. Figure 2 shows that the PAL circuit 25 controls the operation of the relay 18 through an ON signal TI which is applied to a base of a CT transistor to turn on, ei- transistor TI and to allow the flow of current through of the coil Rl of the relay. Figure 3 shows the voltage rise circuit 21, which is. built around a pulse width modulator circuit (PWM), which is provided, by an integrated circuit UC3844N available from Unitrol and by an inductor 32 of 20 μH. The inductor 32. is. connected on one side to the stem Ve. on the PWM circuit 31 and on its other side a. a. collector of a transistor £) 1. An output pin on the PWM circuit controls the base of the transistor Ql to interrupt or switch the transistor £) 1. The output of the inductor 32 is connected through the diode D5 to the NC contact of the relay 18 (Figure 2). The PWM circuit 31 is enabled through an ENABLE line from the controller 30 which turns on a transistor Q2 to provide a path to ground for the PWM circuit 31. The PWM circuit 31 has appropriate deviation networks to control the signal coming from the OUT terminal that controls the output of the inductor 32. The inductor 32 has the reserve battery voltage RES. fed to one input side, and the output is controlled by the PWM circuit 31. The turning on and off of the PWM circuit causes the voltage at the inductor output to increase to a level higher than the 13.1 to 13.4 volts observed in the backup battery. Switching or interruption produces an output voltage of approximately 14.0 volts bDC. The output of the inductor 32 is coupled to the comparators observed in Figure 2 to detect the voltage level of the starting battery. The output of the inductor 32 is also connected to the normally closed (NC) contact of the relay 18 which, when the relay is in the normally closed state, it is connected to the HPB starter battery.

Operation The vehicle engine is defined as having three states: 1) rest, 2) start and 3) run. The controller 30 detects these states by detecting the state of the ignition switch represented by the ON and START switches in Figure 1.

When the vehicle is at rest and the starting battery voltage decreases to a preselected level, such as 12.75 volts DC, this means that the vehicle has been off for a prolonged period of time such as one month. Then, the charging circuit 20 is enabled to allow the backup battery RES. charge the HPB starter battery, provided that the backup battery is at a voltage of at least 12.2 volts DC which means that it is at its charge level. One of the comparators 28 detects the threshold of 12.2 volts for the reserve battery RES. One of the comparators 29 detects the threshold of 12.75 volts for the HPB starter battery. The charging circuit -20 is enabled for a period of time determined by the logic in the PAL 25 and the voltage sensor of the HPB battery. When the vehicle engine is running, this is detected by the controller 30, and with the condition that the reserve battery voltage RES. exceeding the upper threshold +13.4 volts, the relay 18 will be energized to cause movable contact in the relay to make contact with the contact of the open position. During this twenty minute period, the load will flow from the alternator 14 to the backup battery RES. and the HPB starting battery through the PTC resistor 19. When the timer or synchronizer starts to run or when the backup battery drops below the 13.1 volt threshold, this indicates that the backup battery is too low to be used. to recharge IB. starter battery. The relay 18 will be in the normally closed position (-NC), but the ENABLE signal to the charging circuit 20 will be disabled to connect the starting battery 14 from the receiving charge from the RES backup battery. This will allow the alternator 14 to charge the reserve battery RES. and will protect it against discharge through the HPB starter battery. Conversely, if the starting battery voltage rises above the 14.0 volt threshold for more than a predetermined period of time, this represents a fully charged condition for the HPB starter battery and it will no longer accept the resulting load. of the backup battery RES., so that the relay 18 will be de-energized and the charging circuit 20 is disabled to protect the charging condition of the RES backup battery. and to prevent overcharging of the starting battery. When the load on the HPB starter battery falls below 13.8 volts, and it is assumed that the vehicle engine is running, the PAL 25 circuit will energize the relay 18 to allow charging of the starting battery ÜPB from the alternator 14 to through the PTC resistor 19. A third function is provided when the car is starting. If the controller 30 detects that the reserve battery is below some threshold, such that the reserve battery is dead, it will not start at the first operation of the ignition switch, but will start at the second attempt. It should be appreciated that in an alternative embodiment, the components shown within the dashed lines in Figure 2 as the controller 30 may be replaced with an equivalent microelectronic CPU, suitably programmed to provide the functions described herein. Some external synchronization circuit would be required to provide the synchronization signals for such a CPU circuit. Such a circuit can have analog-to-digital inputs to detect battery voltage levels. And, while in the illustrated modes, a relay 18 is a turn-on or turn-off device that controls the connection of the HPB starter battery to various charging sourcesIt should be understood that the various types and numbers of semiconductor devices could be substituted to perform this function without departing from the scope of the invention. It will be appreciated that the threshold voltages are representative of the preferred voltages, and that various systems in the vein may require different voltage thresholds. Likewise, the different synchronizer or timer values are representative of the preferred values although other values may be chosen without departing from the scope of the present invention. Furthermore, it will be understood that other details of the preferred embodiment and the alternative embodiment may be varied without departing from the spirit of the invention, as defined by the following claims.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention is that it is clear from the present description of the invention.

Claims (18)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A circuit for controlling the charging of a starting load energy source in a vehicle, and for controlling a load supply from a reserve charging power source in the vehicle, the circuit includes a one-way charging circuit circuit between the starting charge power source and the reserve charge power source for converting a voltage from the reserve charge power source to a voltage necessary to fully charge the starting charge power source, and a driver operably connected to detect the load level on the starting load power source and on the reserve load power source, the controller enables and disables the load circuit to connect and disconnect the load power source of the load. start to the charging circuit, in response to the voltage level over the starting load power source, in response to the voltage level over the power source reserve circuit, and in response to an on-off state of a vehicle engine, the circuit is characterized by: a switchable device connected in the circuit path from the starting load power source to the source of reserve charging power, the switchable device is switchable to disconnect the charging load power source from the charging circuit and to connect the charging charging power source to the reserve charging power source and an alternator.

2. The circuit according to claim 1, characterized in that the controller is further operable to connect the backup charge power source to the starting charge power source, through the charging circuit in response to a trip condition of the vehicle as represented by a voltage level on the starting load energy source.

3. The circuit according to claim 1, characterized in that the controller is further operable to couple the charging current from the reserve charging power source to the starting charging power source, for a predetermined period of time in response to a lit condition of the vehicle.

4. The circuit according to claim 1, characterized in that the switchable device is a relay.

5. The circuit according to claim 1, characterized in that it also comprises a circuit path from the alternator to the starting load energy source, and because it also comprises a current limiting device in the circuit path.

6. The circuit according to claim 5, characterized in that the current limiting device is a resistance of positive temperature coefficient in the circuit path.

7. The circuit according to claim 1, characterized in that the controller includes a programmable logic circuit and a synchronization circuit.

8. The circuit according to claim 1, characterized in that the starting load energy source is optimized for a high discharge speed during the starting operations of the vehicle.

9. The circuit according to claim 1, characterized in that the energy source of the reserve charge is optimized for the total energy capacity.

10. The circuit in accordance with the. claim 1, characterized in that the controller is operable to detect a voltage potential of one of the starting load power source and the reserve load power source, with respect to a threshold and to selectively decouple the power source from the load. reserve charge of the starting load energy source after detection of the voltage potential in relation to the threshold.

11. The circuit according to claim 10, characterized in that the threshold represents a fully charged condition for the starting load energy source.

12. The circuit according to claim 10, characterized in that the threshold is a low condition of the battery for the reserve charging power source.

13. The circuit according to claim 1, characterized in that the starting load energy source is a battery.

14. The circuit according to claim 1, characterized in that the backup charging power source is a battery.

15. A method for controlling the charging of a starting load energy source in a vehicle, and for controlling a load supply from a reserve charging power source in the vehicle, the method is characterized in that it comprises: load level on the starting load energy source; the detection of the load level on the reserve charge energy source; the detection of the on-off status of the engine of a vehicle; electrically connecting the starting charge power source through a charging circuit to the reserve charging power source or electrically connecting the starting charge power source to the reserve power source and to an alternator in response at the voltage level on the starting load power source, in response to the voltage level on the reserve load power source, and in response to the on-off state of the vehicle engine; and converting a voltage from the reserve charge power source to a voltage necessary to fully charge the starting charge power source.

16. The method according to claim 15, characterized in that the connection of the starting load energy source through the charging circuit is to the reserve charging power source in response to the off condition of a vehicle, as is represented by the voltage level on the starting load energy source.

17. The method according to claim 15, characterized in that the connection of the starting load energy source through the charging circuit is for a predetermined period of time in response to the ignition condition of a vehicle.

18. The method according to claim 15, characterized in that it further comprises detecting a voltage potential of one of the starting load energy source and the reserve charging power source with respect to a threshold and electrically disconnecting in a Selective the backup charge power source of the starting charge power source after detection of the voltage potential in relation to said threshold.