Apparatus and method for controlling charging and discharging of batteries

An apparatus is electrically connected to a battery unit consisting of multiple batteries, an energy conversion system, and power-driven equipment. The apparatus sets number requirements of batteries to be connected to a discharge unit and a charge unit of the battery unit. When the power-driven equipment is started, the apparatus receives an open-circuit voltage of each battery detected by a sensor connected to the battery, and establishes connections of the batteries with the discharge unit or the charge unit according to the open-circuit voltages of the batteries and the number requirements. During the discharge unit supplying power to the power-driven equipment and the energy conversion system charging the charge unit, the apparatus monitors variations of the open-circuit voltages of the batteries, and switches the connections of batteries with the discharge unit or the charge unit according to associations between open-circuit voltages, cut-off discharge voltages, and nominal voltages of the batteries.

BACKGROUND

1. Technical Field

The embodiments of the present disclosure relate to automatic control systems and methods, and more particularly to an apparatus and a method for controlling charge and discharge of batteries.

2. Description of Related Art

Often a battery unit consisting of multiple batteries is applied in an electric automobile. Due to differences in physical characteristics, different batteries may have different nominal voltages. In the factory, variations in the different nominal voltages may be very small. However, in use, the variations may increase over time, and because all the batteries in the unit are charged to the same nominal voltage, some batteries may be regularly overcharged affecting battery performance and shortening the useful life of the batteries.

DETAILED DESCRIPTION

In general, the word “module”, as used herein, refers to logic embodied in hardware or software, or to a collection of software instructions, written in a programming language, such as, Java, C, or assembly. One or more software instructions in the modules may be embedded in firmware, such as in an erasable programmable read only memory (EPROM). The modules described herein may be implemented as either software and/or hardware modules and may be stored in any type of non-transitory computer-readable medium or other storage device. Some non-limiting examples of non-transitory computer-readable media include CDs, DVDs, BLU-RAY, flash memory, and hard disk drives.

FIG. 1is a block diagram of one embodiment of an application environment of an apparatus2for controlling charging and discharging of batteries10in a battery unit1. In this embodiment, the apparatus2is electrically connected to the battery unit1, an energy conversion system3, and power-driven equipment4. The energy conversion system3may include solar power generation apparatuses, wind power generation apparatuses, and electronic chargers. The power-driven equipment4may include one or more engines in an electric automobile, in-car entertainment, and an in-car navigation system, for example.

The battery unit1includes a discharge unit11and a charge unit12, which are connectable to at least some of a plurality of batteries10. As shown inFIG. 1andFIG. 2, some of the batteries10are connected to the discharge unit11through a discharge cascade bus14, and some of the batteries10are connected to the charge unit12through a charge cascade bus15. The energy conversion system3charges batteries10connected to the charge unit12. The batteries10connected to the discharge unit11provides power to the power-driven equipment4. Each battery10is connected to a sensor13, which detects voltage data of the battery10, and sends the voltage data to the apparatus2. The apparatus2exchanges connections of the batteries10with the discharge unit11and the charge unit12based on variations in the voltage data.

As shown inFIG. 3, the apparatus2includes a plurality of functions modules, such as a parameter setting module21, a voltage monitoring module22, a battery grouping module23, and an alarm module24. The apparatus2further includes a microprocessor25and a storage device26. The modules21-24may comprise computerized code in the form of one or more programs that are stored in the storage device26. The computerized code includes instructions that are executed by the microprocessor25, to provide the aforementioned functions of the apparatus2. A detailed description of the functions of the modules21-24is given below with reference toFIG. 4andFIG. 5. The storage device26may be a cache or a dedicated memory, such as an EPROM, a hard disk driver (HDD), or flash memory.

FIG. 4is a flowchart of one embodiment of a method for controlling charge and discharge of the batteries10in the battery unit1. Depending on the embodiment, additional steps may be added, others removed, and the ordering of the steps may be changed.

In step S10, the parameter setting module10sets number requirements of the batteries10to be connected to the discharge unit11and the charge unit12of the battery unit1, and sets a cut-off discharge voltage and a nominal voltage of each battery10. For example, a first number N1 of the batteries10to be connected to the discharge unit11may be set as a first proportion (such as 50%) of a total number N of the batteries10in the battery unit1, or be set as more than the first proportion but less than a second proportion (such as 90%) of the total number N. A second number N2 of the batteries10to be connected to the charge unit12may be equal to (N−N1). A cut-off discharge voltage of a battery10is a voltage at which the battery10is considered fully discharged, and to stop discharge otherwise the battery10may be damaged. A nominal voltage of the battery10is a typical voltage when the battery10works with a usual temperature.

In step S20, when the power-driven equipment is started, each sensor13connected to a battery10detects an open-circuit voltage of the battery10. The open-circuit voltage of the battery10is a difference of electrical potential between a positive terminal and a negative terminal of the battery10. The voltage monitoring module22receives the open-circuit voltages of all of the batteries10sent by the sensors13. The battery grouping module23establishes connections between the batteries10and the discharge unit11and the charge unit12according to the open-circuit voltages of the batteries10and the number requirements. For example, the battery grouping module23selects the N1 batteries10that have higher open-circuit voltages, sends signals to some control circuits to enable connections between the selected batteries10and the discharge unit11, and enable connections between the remaining batteries10and the charge unit12.

In step S30, the voltage monitoring module22monitors variations of the open-circuit voltages of the batteries10during the discharge unit11supplying power to the power-driven equipment4and the energy conversion system3charging the charge unit12.

In step S40, the battery grouping module23switches connections of one or more first batteries10from the discharge unit11to the charge unit12, to avoid over discharge of the first one or more batteries10, where a current open-circuit voltage of each first battery10is lower than the cut-off discharge voltage of the first buttery10. A detailed description of step S40is given inFIG. 5and below.

In step S50, the battery grouping module23switches connections of one or more second batteries10from the charge unit12to the discharge unit11, to avoid over charge of the second one or more batteries10, wherein a current open-circuit voltage of each second battery10equals the nominal voltage of the second battery10. A detailed description of step S50is given inFIG. 6and below.

FIG. 5is a flowchart detailing step S40ofFIG. 4. Depending on the embodiment, additional steps may be added, others removed, and the ordering of the steps may be changed.

In step S402, the voltage monitoring module22determines the one or more first batteries10by comparing the current open-circuit voltages with the cut-off discharge voltages of the batteries10connected to the discharge unit11. For example, if the cut-off discharge voltage of a battery10connected to the discharge unit11is 12V, but the current open-circuit voltage of the battery10is 10V, then the battery10is determined as a first battery10, which needs to be connect to the charge unit12.

In step S404, the voltage monitoring module22selects one first battery10, such as the battery10has the current open-circuit voltage 10V.

In step S406, the voltage monitoring module22checks if the charge unit12has been connected with a preset number of third batteries10, where each third battery10has a current open-circuit voltage that equals or is more than a cut-off discharge voltage of the third battery10. For example, in this embodiment, the preset number may be set as a third proportion (such as 10%) of a total number N of the batteries10in the battery unit1. If the charge unit12has been connected with the preset number of third batteries10, the procedure directly goes to step S410. If the charge unit12has not been connected with the preset number of third batteries10, in step S408, the alarm module24sends a signal to alert users that the battery unit1has low battery charges. The signal may be an audio signal output by a speaker, or a message displayed on a display device (not shown) of the apparatus2. Then, the procedure goes to step S410.

In step S410, the battery grouping module23switches the connection of the first battery10from the discharge unit11to the charge unit12, and switches a connection of a battery10, which is connected to the charge unit12and has a highest current open-circuit voltage compared to other batteries10connected to the charge unit12, from the charge unit12to the discharge unit11. For example, the first battery10has the current open-circuit voltage 11.9V may be switched to connect to the charge unit12, and a battery10connected to the charge unit12that has the highest current open-circuit voltage 36V may be switched to connect to the discharge unit11.

In step S412, the voltage monitoring module22determines if there is any battery in the battery unit1that has a present open-circuit voltage higher than the cut-off discharge voltage of the battery10. If there is a battery in the battery unit1that has a current open-circuit voltage higher than the cut-off discharge voltage of the battery10, the discharge unit11continuously providing power to the power-driven equipment, and the procedure returns to step S404. Otherwise, if the current open-circuit voltage of each battery10in the battery unit1equals or is less than the cut-off discharge voltage of the battery10, in step S414, the alarm module24informs the discharge unit12to stop supplying power to the power-driven equipment4.

FIG. 6is a flowchart detailing step S50inFIG. 4. Depending on the embodiment, additional steps may be added, others removed, and the ordering of the steps may be changed.

In step S502, the voltage monitoring module22determines the one or more second batteries10connected to the charge unit12by comparing the current open-circuit voltages with the nominal voltages of the batteries10connected to the charge unit12. For example, if the nominal voltage and the current open-circuit voltage of a battery10connected to the charge unit12are both 24V, the battery10is determined as a second battery10to be connected to the discharge unit11.

In step S504, the voltage monitoring module22selects one second battery10, such as the battery10has the current open-circuit voltage 24V.

In step S506, the battery grouping module23switches the connection of the second battery10from the charge unit12to the discharge unit11, and switches a connection of a battery10, which is connected to the discharge unit11and has a lowest current open-circuit voltage compared to other batteries10connected to the discharge unit11, from the discharge unit11to the charge unit12. For example, the second battery10has the current open-circuit voltage 24V may be connected to the discharge unit11, and the battery10that connected to the discharge unit11and has the lowest current open-circuit voltage 8V may be connected to the charge unit12.

In step S508, the voltage monitoring module22determines if there is any battery10in the battery unit1that has a current open-circuit voltage lower than the nominal voltage of the battery10. If there is a battery10that has a current open-circuit voltage lower than the nominal voltage of the battery10, the energy conversion system3continuously charges the charge unit12, and the procedure returns to step S504. Otherwise, if the current open-circuit voltage of each battery10in the battery unit1equals the nominal voltage of the battery10, step S510is implemented.

In step S510, the alarm module24sends a signal to alert the users that the charge unit12has completed charging. The signal may be an audio signal output by the output device, such as the speaker and/or a message displayed on the display device (not shown) of the apparatus2.