Sodium battery emergency power supply with protection function and control method
By designing a sodium battery emergency power supply with protective functions, the problems of poor safety and reversibility of sodium battery emergency power supplies have been solved, achieving stable output and extended usage time in different environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-07
- Publication Date
- 2026-04-07
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing lithium-ion battery emergency power supplies have short lifespans and uncertain operating times, while sodium-ion batteries have poor safety and reversibility as emergency power sources.
A sodium battery emergency power supply with protective functions was designed, including a control unit, a detection unit, a charging unit, an inverter unit, an output unit, and a protection unit. The power supply controls the working mode by detecting electrical parameter data, and performs current limiting and voltage regulation to achieve voltage protection, current protection, and temperature protection.
It improves the output efficiency of emergency power supplies, extends their service life, enhances their adaptability and stability in different environments, and ensures the safety and reversibility of sodium battery emergency power supplies.
Smart Images
Figure CN121813626A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power control technology, specifically to a sodium battery emergency power supply with protective functions and its control method. Background Technology
[0002] In today's society, people's work and life are inseparable from electricity; without power supply, normal order is disrupted. With the continuous development of technology, emergency power supplies are increasingly widely used in various fields. A UPS (Uninterruptible Power Supply) is designed to solve the problem of uninterrupted power supply. It connects a battery to a main unit, and through the main unit's inverter and other module circuits, converts DC power into AC power. UPS emergency power supplies are used in important buildings for emergency lighting, accident lighting, and fire protection facilities. They mainly consist of an input unit, output unit, charging module, battery pack, inverter, monitor, and output switching device. This system can provide emergency power in emergency situations. Sodium batteries are a type of high-temperature sodium battery, characterized by stable product properties, high safety, long service life, wide application range, readily available and non-toxic raw materials, and simple and pollution-free waste recycling processes. In existing technologies, lithium battery emergency power supplies have short lifespans and uncertain operating times. Furthermore, sodium batteries, as the main core component of emergency power supplies, have poor safety and reversibility. Summary of the Invention
[0003] The purpose of this invention is to provide a sodium battery emergency power supply and control method with protective function in order to solve at least one of the above-mentioned technical problems.
[0004] In a first aspect, embodiments of the present invention provide a sodium battery emergency power supply with protective functions, comprising: a control unit, a sodium battery pack, a charging unit, a detection unit, an inverter unit, an output unit, and a protection unit; wherein, the detection unit is used to detect electrical parameter data of each unit of the sodium battery emergency power supply; the control unit is used to control the operating mode of the sodium battery emergency power supply based on the electrical parameter data; the charging unit is used to charge the sodium battery pack and to perform current limiting and voltage regulation during the charging process; the inverter unit and the output unit are used to output power matching to the load; and the protection unit is used to provide voltage protection, current protection, and temperature protection for the sodium battery emergency power supply.
[0005] Optionally, the detection unit includes a voltage sensor, a current sensor, a temperature sensor, and a power sensor; the electrical parameter data includes voltage data, current data, temperature data, and power data.
[0006] Optionally, the charging unit includes a charging interface, a reverse connection protection device, a voltage regulating device, a charging current limiting device, and a charging voltage limiting device; wherein, the voltage regulating device is used to regulate the charging voltage of the sodium battery pack; the charging current limiting device and the charging voltage limiting device are used to limit the charging current and charging voltage of the sodium battery pack, respectively.
[0007] Optionally, the output unit includes an automatic switching device, a power matching device, and a voltage conversion device; the automatic switching device is used to switch the power supply of the load to the sodium battery emergency power supply based on the instructions of the control unit; the voltage conversion device is used to convert the output voltage of the sodium battery emergency power supply into the input voltage of the load; and the power matching device is used to match the output power of the sodium battery emergency power supply with the power demand of the load.
[0008] Optionally, the inverter unit includes power devices, switching devices, and a transformer; the power devices include insulated-gate field-effect transistors and insulated-gate bipolar transistors.
[0009] Optionally, the protection unit includes a voltage protection module, a current protection module, and a temperature protection module; wherein, the voltage protection module is used to protect the sodium battery emergency power supply by voltage; the current protection module is used to protect the sodium battery emergency power supply by current; and the temperature protection module is used to protect the sodium battery emergency power supply by temperature.
[0010] Optionally, the sodium battery pack includes at least two sets of sodium-ion batteries connected in parallel, a state detection module, a heating device, and a heat dissipation device; wherein, the state detection module is used to detect the health status of the sodium-ion batteries; the heating device and the heat dissipation device are used to heat and dissipate heat from the sodium-ion batteries, respectively.
[0011] Secondly, embodiments of the present invention also provide a control method for a sodium battery emergency power supply with protective functions. The method includes: acquiring electrical parameter data of each unit of the sodium battery emergency power supply based on a detection unit; determining the operating mode of the sodium battery emergency power supply based on the electrical parameter data; the operating mode including a charging mode and a discharging mode; and performing corresponding control on the sodium battery emergency power supply based on the operating mode.
[0012] Optionally, when the operating mode is charging mode, corresponding control is performed on the sodium battery emergency power supply, including: detecting electrical parameter data of each unit based on the detection unit and transmitting the electrical parameter data to the control unit; detecting battery pack status data based on the sodium battery pack status detection device and transmitting the battery pack status data to the control unit; determining the access voltage range based on the electrical parameter data and the battery pack status data, selecting the corresponding channel for charging, and controlling the charging power of the charging unit and monitoring the electrical parameter data of each unit; if the electrical parameter data is abnormal, controlling the protection unit to perform abnormal protection on the sodium battery emergency power supply; detecting the temperature of the sodium battery pack during charging and controlling the temperature of the sodium battery pack within a preset temperature range based on the control unit; determining whether the sodium battery pack is fully charged, and if so, disconnecting the charging unit.
[0013] Optionally, when the operating mode is discharge mode, corresponding control is performed on the sodium battery emergency power supply, including: connecting the sodium battery emergency power supply to the load; detecting data through a detection unit to obtain current load information; detecting whether the load is working normally based on the current load information; if yes, controlling the sodium battery emergency power supply not to output; if no, adjusting the output parameters of the sodium battery emergency power supply according to the electrical parameters required by the load; monitoring the status of the sodium battery pack during the discharge process of the sodium battery emergency power supply to obtain battery pack status information; if the battery pack status information is abnormal, controlling the protection unit to perform abnormal protection on the sodium battery emergency power supply.
[0014] This invention provides a sodium battery emergency power supply and control method with protective functions, ensuring that the emergency power supply can work stably under various temperature environments, improving the output efficiency of the emergency power supply, extending the service life of the emergency power supply, and ensuring that the emergency power supply can be used in different application environments and operating conditions, thus alleviating the technical problems of low safety and poor reversibility of sodium batteries in the prior art. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0016] Figure 1 A schematic diagram of a sodium battery emergency power supply with protective functions provided in an embodiment of the present invention; Figure 2A flowchart illustrating a control method for a sodium battery emergency power supply with protective functions, provided in an embodiment of the present invention; Figure 3 A flowchart of a charging mode control method provided in an embodiment of the present invention; Figure 4 This is a flowchart of a discharge mode control method provided in an embodiment of the present invention. Detailed Implementation
[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0018] Figure 1 This is a schematic diagram of a sodium battery emergency power supply with protective functions according to an embodiment of the present invention. Figure 1 As shown, it includes: a control unit 10, a sodium battery pack 20, a charging unit 30, a detection unit 40, an inverter unit 50, an output unit 60, and a protection unit 70; wherein, The detection unit 40 is used to detect the electrical parameter data of each unit of the sodium battery emergency power supply. Control unit 10 is used to control the working mode of the sodium battery emergency power supply based on electrical parameter data; The charging unit 30 is used to charge the sodium battery pack and to limit the current and regulate the voltage during the charging process. Inverter unit 50 and output unit 60 are used to output power-matched electrical power to load 80; Protection unit 70 is used to provide voltage protection, current protection and temperature protection for sodium battery emergency power supply.
[0019] Specifically, the control unit 10 mainly controls the various modules of the emergency power supply by receiving data from the detection unit to ensure the reliable performance of the emergency power supply. At the same time, it monitors the emergency power supply in real time and sends instructions to the protection unit for protection as soon as a problem is detected.
[0020] Specifically, the detection unit 40 includes a voltage sensor, a current sensor, a temperature sensor, and a power sensor; the electrical parameter data includes voltage data, current data, temperature data, and power data. The detection unit 40 mainly detects the health status of each unit in the emergency power supply, such as current, voltage, temperature, and connected load status, providing data support for the control unit 10.
[0021] Specifically, the charging unit 30 includes a charging interface, a reverse connection protection device, a voltage regulation device, a charging current limiting device, and a charging voltage limiting device; wherein, A voltage regulating device is used to regulate the charging voltage of the sodium battery pack; The charging current limiting device and the charging voltage limiting device are used to limit the charging current and charging voltage of the sodium battery pack, respectively.
[0022] Specifically, the charging unit 30 is mainly used to charge the sodium battery pack of the emergency power supply. Through the detection of the detection unit, the control unit limits the voltage and current of the charging unit to ensure fast and reliable charging. Through the voltage regulation device, the input voltage range is adjusted to be suitable for charging emergency power supplies with different voltage levels.
[0023] Specifically, the output unit 60 includes an automatic switching device, a power matching device, and a voltage conversion device; wherein, An automatic switching device is used to switch the power supply of the load to sodium battery emergency power based on instructions from the control unit. A voltage conversion device is used to convert the output voltage of a sodium battery emergency power supply into the input voltage of a load; A power matching device is used to match the output power of the sodium battery emergency power supply with the power demand of the load.
[0024] In this embodiment of the invention, the output unit 60 mainly controls the automatic switching device of the output power supply according to the instructions of the control unit, so as to ensure that when the normal power supply to the load stops, the emergency power supply can take over and continuously output power, while ensuring constant power output according to different loads.
[0025] Specifically, the inverter unit 50 includes power devices, a switching device, and a transformer; the power devices include insulated-gate field-effect transistors (MOS) and insulated-gate bipolar transistors (IGBTs). In this embodiment of the invention, the inverter unit 50 is used to switch different power devices and transformer pairs according to the switching device to convert the power supply of the battery pack into the required load power supply, which is then provided to the output unit for power output.
[0026] Specifically, the protection unit 70 includes a voltage protection module, a current protection module, and a temperature protection module; wherein, Voltage protection module, used for voltage protection of sodium battery emergency power supply; The current protection module is used to protect the sodium battery emergency power supply from the current. The temperature protection module is used to protect the sodium battery emergency power supply from temperature fluctuations.
[0027] In this embodiment of the invention, the protection unit 70 is used to protect against problems that occur in the emergency power supply, ensuring the power supply's continuous and highly reliable output.
[0028] Specifically, the sodium battery pack 20 includes at least two sets of sodium-ion batteries connected in parallel, a state detection module, a heating device, and a heat dissipation device; wherein, The status detection module is used to detect the health status of the sodium-ion battery; The heating device and the heat dissipation device are used to heat and dissipate heat from the sodium-ion battery, respectively.
[0029] In this embodiment of the invention, the sodium battery pack 20 consists of two groups of sodium-ion batteries, each connected in series and parallel. This reduces the risk of the entire emergency power supply failing if one battery fails. The two groups can be used interchangeably or simultaneously, depending on the scenario, ensuring constant power output and increasing the lifespan of the sodium batteries in the emergency power supply. The status detection module primarily detects the temperature, voltage, current, and condition of the battery pack. This data is fed back to the control unit, and compared with the detection unit's feedback on the sodium battery pack. This allows for control of the sodium battery pack's temperature, determination of whether the pack is damaged, and whether the connected batteries need replacement. The heating and heat dissipation devices, based on the temperature detection data, heat and dissipate heat from the sodium battery pack, ensuring the emergency power supply can operate normally under various extreme temperatures.
[0030] Figure 2 This is a flowchart of a control method for a sodium battery emergency power supply with protective functions according to an embodiment of the present invention. Figure 2 As shown, the method specifically includes the following steps: Step S202: Obtain electrical parameter data of each unit of the sodium battery emergency power supply based on the detection unit.
[0031] Step S204: Based on electrical parameter data, determine the operating mode of the sodium battery emergency power supply; the operating mode includes charging mode and discharging mode.
[0032] In an optional embodiment of this invention, the system is divided based on data from the charging unit and the output unit. Simultaneously, based on the state of charge of the sodium battery pack, when the charging unit detects current and the sodium battery pack's charge is increasing, it is considered to be in charging mode; when the output unit outputs current and the sodium battery pack's charge is decreasing, it is considered to be in discharging mode. The emergency power supply provided by this invention eliminates the phenomenon of simultaneous discharging and charging, reducing battery damage.
[0033] Step S206: Based on the operating mode, perform corresponding control on the sodium battery emergency power supply.
[0034] Figure 3 This is a flowchart of a charging mode control method according to an embodiment of the present invention. Figure 3As shown, when the operating mode is charging mode, the sodium battery emergency power supply is controlled accordingly, including the following steps: Step S301: Based on the detection unit, detect the electrical parameter data of each unit and transmit the electrical parameter data to the control unit; Step S302: The state detection device of the sodium battery pack detects the state data of the battery pack and transmits the state data of the battery pack to the control unit. Step S303: Based on electrical parameter data and battery pack status data, determine the access voltage range, select the corresponding channel for charging, and control the charging power of the charging unit and monitor the electrical parameter data of each unit. Step S304: If the electrical parameter data is abnormal, the control and protection unit will perform abnormal protection for the sodium battery emergency power supply. Step S305: Detect the temperature of the sodium battery pack during charging, and control the temperature of the sodium battery pack within a preset temperature range based on the control unit. Step S306: Determine whether the sodium battery pack is fully charged. If so, disconnect the charging unit.
[0035] Specifically, controlling the charging power of the charging unit is mainly achieved by limiting the charging voltage or current through charging current limiting devices and charging voltage limiting devices, ensuring that the input voltage and current are within an adjustable range. Selecting different channels for charging is mainly achieved through the voltage adjustment device of the charging unit, which distinguishes between DC input voltage and AC input voltage. The AC voltage is further divided into two levels: 110V and 220V, and the DC voltage is divided into two levels: 24V and 48V. Based on different input voltages, the control unit controls the charging unit to connect to different channels to charge the sodium battery pack.
[0036] Specifically, temperature control refers to controlling the heating and cooling devices inside the sodium battery pack, primarily based on the temperature data from the state detection module and supplemented by the temperature data from the detection unit, to ensure that the sodium battery pack operates in a relatively mild environment.
[0037] Preferably, the heating device mainly involves installing the sodium battery pack in a groove of a heating mesh, with a certain installation distance between the heating mesh and the sodium battery pack to ensure that heat is radiated to the battery pack; the heat dissipation device mainly involves installing heat sinks on the top of the sodium battery pack, and installing a fan on the heat sinks. The main control power supply controls the fan speed through PWM to achieve a temperature reduction.
[0038] Figure 4 This is a flowchart of a discharge mode control method provided by an embodiment of the present invention. Figure 4As shown, when the operating mode is discharge mode, the sodium battery emergency power supply is controlled accordingly, including the following steps: Step S401: Connect the sodium battery emergency power supply to the load; Step S402: Data is detected by the detection unit to obtain the current load information; for example, the current load information includes voltage, current, power, and whether it is working normally. Step S403: Based on the current load information, check whether the load is working normally; if yes, proceed to step S404; if no, proceed to step S405. Step S404: Control the sodium battery emergency power supply to stop outputting; Step S405: Adjust the output parameters of the sodium battery emergency power supply according to the electrical parameters required by the load. Step S406: During the discharge process of the sodium battery emergency power supply, the status of the sodium battery pack is monitored to obtain the battery pack status information. In step S407, if the status information of the battery pack is abnormal, the control and protection unit will perform abnormal protection for the sodium battery emergency power supply.
[0039] Specifically, during the discharge process, different combinations of sodium-ion batteries are switched according to the state information of the sodium battery pack to ensure that the output power is met, while ensuring that the application time of the sodium-ion batteries in the sodium battery pack can reach an average level.
[0040] Specifically, the detection unit determines the load's power status, such as whether it's DC or AC voltage, and whether it's 24V or 220V. The power matching and voltage conversion devices in the control output unit then meet these requirements.
[0041] Specifically, the main fault in sodium battery packs is short-circuit fault. The operating current of a sodium battery pack mainly flows through the series branches, while the parallel branches are mainly for balancing current. If one cell experiences an internal short circuit, the other cells will generate internal short-circuit current flowing towards the cell with the internal short circuit. This allows the location of the cell with the internal short circuit to be determined, and the protection unit will switch off the cell with the secondary short circuit to ensure the battery continues to operate.
[0042] Specifically, the faults in each unit are mainly voltage and current faults in the charging unit, output unit, and inverter unit. The occurrence rate of these faults can be reduced by adjusting the control unit.
[0043] As described above, the present invention provides a sodium battery emergency power supply and control method with protective functions, which has the following technical advantages compared with the prior art: 1. Features temperature detection and control, internal short-circuit detection and protection, and constant power output. Fault detection ensures the sodium battery emergency power supply maintains constant power output under varying loads. Internal short-circuit detection and protection extend the lifespan of the emergency power supply. Temperature detection ensures stable operation under various temperature conditions, improving output efficiency and extending service life. This allows the emergency power supply to be used in diverse application environments and operating conditions.
[0044] 2. It has an output unit, including an automatic switching device, a power matching device, and a voltage conversion device, which improves the adaptability of the emergency power supply. It can adjust different power and voltage levels of output, improve environmental adaptability, and at the same time ensure stable power output, thereby improving the stability of the system when the load is powered.
[0045] 3. The charging unit includes a charging interface, reverse connection protection, voltage regulation, current limiting, and voltage limiting, enhancing the safety of emergency power supply charging. It also features adjustable voltage and current during charging to ensure fast charging. It can accept different charging voltages, ensuring environmental adaptability.
[0046] 4. It features a sodium battery pack, mainly consisting of sodium-ion batteries, a status detection module, a heating device, and a heat dissipation device, which improves the safety performance of the battery pack, enhances the environmental adaptability of the battery, increases the battery's service life, and broadens the temperature range for battery applications.
[0047] 5. It has an inverter unit, which is used to switch different power devices and transformer pairs according to the switching device to convert the power of the battery pack into the required load power and provide it to the output unit for power output; thus improving the application range of the emergency power supply and ensuring constant power output.
[0048] 6. The control method is divided into charging and discharging processes, with different adjustment methods for each process. At the same time, the information of each data is detected to ensure the safe and reliable operation of each process, ensuring stable power output, improving the stability and reliability of the entire emergency power supply, ensuring the safety of the important component battery pack, and making it suitable for different application scenarios and environments.
[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A sodium battery emergency power supply with protective functions, characterized in that, include: The system includes a control unit, a sodium battery pack, a charging unit, a detection unit, an inverter unit, an output unit, and a protection unit; among which, The detection unit is used to detect the electrical parameter data of each unit of the sodium battery emergency power supply; The control unit is used to control the working mode of the sodium battery emergency power supply based on the electrical parameter data; The charging unit is used to charge the sodium battery pack and to limit the current and regulate the voltage during the charging process. The inverter unit and the output unit are used to output power matched to the load; The protection unit is used to provide voltage protection, current protection, and temperature protection for the sodium battery emergency power supply.
2. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The detection unit includes a voltage sensor, a current sensor, a temperature sensor, and a power sensor; the electrical parameter data includes voltage data, current data, temperature data, and power data.
3. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The charging unit includes a charging interface, a reverse connection protection device, a voltage regulator, a charging current limiting device, and a charging voltage limiting device; wherein, The voltage regulating device is used to regulate the charging voltage of the sodium battery pack; The charging current limiting device and the charging voltage limiting device are used to limit the charging current value and the charging voltage value of the sodium battery pack, respectively.
4. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The output unit includes an automatic switching device, a power matching device, and a voltage conversion device; The automatic switching device is used to switch the power supply of the load to the sodium battery emergency power supply based on the instructions of the control unit. The voltage conversion device is used to convert the output voltage of the sodium battery emergency power supply into the input voltage of the load; The power matching device is used to match the output power of the sodium battery emergency power supply with the power demand of the load.
5. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The inverter unit includes power devices, switching devices, and a transformer; the power devices include insulated-gate field-effect transistors and insulated-gate bipolar transistors.
6. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The protection unit includes a voltage protection module, a current protection module, and a temperature protection module; wherein... The voltage protection module is used to provide voltage protection for the sodium battery emergency power supply; The current protection module is used to provide current protection for the sodium battery emergency power supply; The temperature protection module is used to protect the sodium battery emergency power supply from temperature.
7. The sodium battery emergency power supply with protective function according to claim 1, characterized in that: The sodium battery pack includes at least two sets of sodium-ion batteries connected in parallel, a state detection module, a heating device, and a heat dissipation device; wherein, The status detection module is used to detect the health status of the sodium-ion battery; The heating device and the heat dissipation device are used to heat and dissipate heat from the sodium-ion battery, respectively.
8. A control method for a sodium battery emergency power supply with protective function as described in any one of claims 1-7, characterized in that: The method includes: The electrical parameter data of each unit of the sodium battery emergency power supply are obtained based on the detection unit; Based on the electrical parameter data, the operating mode of the sodium battery emergency power supply is determined; the operating mode includes a charging mode and a discharging mode. Based on the aforementioned operating mode, the sodium battery emergency power supply is controlled accordingly.
9. The method according to claim 8, characterized in that, When the operating mode is charging mode, corresponding control is performed on the sodium battery emergency power supply, including: The detection unit detects the electrical parameter data of each unit and transmits the electrical parameter data to the control unit. The sodium battery pack state detection device detects battery pack state data and transmits the battery pack state data to the control unit. Based on the electrical parameter data and the battery pack status data, the access voltage range is determined, the corresponding channel is selected for charging, and the charging power of the charging unit is controlled and the electrical parameter data of each unit is monitored. If the electrical parameter data is abnormal, the control and protection unit will perform abnormal protection on the sodium battery emergency power supply. The temperature of the sodium battery pack during charging is detected, and the temperature of the sodium battery pack is controlled within a preset temperature range based on the control unit. Determine whether the sodium battery pack is fully charged; if so, disconnect the charging unit.
10. The method according to claim 8, characterized in that, When the operating mode is discharge mode, corresponding control is performed on the sodium battery emergency power supply, including: Connect the sodium battery emergency power supply to the load; The current load information is obtained by detecting data through the detection unit; Based on the current load information, detect whether the load is working properly; If so, then control the sodium battery emergency power supply to not output; If not, adjust the output parameters of the sodium battery emergency power supply according to the electrical parameters required by the load; During the discharge process of the sodium battery emergency power supply, the status of the sodium battery pack is monitored to obtain battery pack status information; If the status information of the battery pack is abnormal, the control and protection unit will perform abnormal protection for the sodium battery emergency power supply.