CN118074247A

CN118074247A - Cleaning system

Info

Publication number: CN118074247A
Application number: CN202211476998.3A
Authority: CN
Inventors: 车现玲; 何大印
Original assignee: Anker Innovations Co Ltd
Current assignee: Anker Innovations Co Ltd
Priority date: 2022-11-23
Filing date: 2022-11-23
Publication date: 2024-05-24

Abstract

The application relates to a cleaning system comprising: a cleaner and a base station interfacing with the cleaner; the cleaning machine is used for sending the self-outbound information to the base station; and the base station is used for stopping outputting the charging voltage when receiving the off-station information or stopping outputting the charging voltage when determining that the cleaning machine leaves the base station according to the change of the current of the base station, wherein the charging voltage is used for charging the cleaning machine. The application can determine whether the cleaning machine leaves the base station from the cleaning machine side or from the base station side, and the base station can stop outputting the charging voltage under the condition that the cleaning machine leaves the base station, thereby saving electric energy, effectively eliminating potential safety hazards and solving the technical problems of resource waste and potential safety hazards caused by the fact that the base station outputs the charging voltage frequently.

Description

Cleaning system

Technical Field

The application relates to the technical field of cleaning robots, in particular to a cleaning system.

Background

With the development of intelligent hardware technology, in recent years, intelligent cleaning robots gradually replace manual traditional sweeping and mopping modes, and can return to a base station for self-cleaning after completing all cleaning tasks, so that the workload of people for cleaning the ground in families is reduced, and the intelligent cleaning robots become small-helper of the families. The cleaning robot can become a household 'small helper', and one of the important functions of the cleaning robot is 'charging'. When the battery level of the cleaner is insufficient to continue the cleaning operation, other devices are required to be charged to supplement the energy.

At present, in the related art, a method for realizing the charging function of a cleaning machine on a base station and a cleaning machine matched product is that the base station always outputs charging voltage, namely, when the cleaning machine is cleaned out of the base station, a charging port of the base station still keeps outputting the charging voltage. The constant output method not only wastes a large amount of electric energy resources, but also has certain potential safety hazards, such as short circuit risks when a small pet enters a charging port in a base station or wears a conductive chain when the cleaner is not in the base station.

Aiming at the problems of resource waste and potential safety hazard caused by the fact that a base station always outputs charging voltage, no effective solution is proposed at present.

Disclosure of Invention

The application provides a cleaning system for solving the technical problems of resource waste and potential safety hazard caused by the fact that a base station outputs charging voltage frequently.

According to one aspect of an embodiment of the present application, there is provided a cleaning system comprising: a cleaner and a base station interfacing with the cleaner; the cleaning machine is used for sending the self-outbound information to the base station; and the base station is used for stopping outputting the charging voltage when receiving the off-station information or stopping outputting the charging voltage when determining that the cleaning machine leaves the base station according to the change of the current of the base station, wherein the charging voltage is used for charging the cleaning machine.

Optionally, the cleaning machine comprises a battery pack and a first communication module, the base station comprises a second communication module, the battery pack is used for storing electric energy, and the first communication module and the second communication module are used for establishing a wireless communication link between the cleaning machine and the base station.

Optionally, the sending of the self-outbound information by the cleaning machine to the base station specifically includes: detecting a first charging current of the battery pack by the cleaner; in the case that the first charging current is less than the first current threshold, the cleaning machine generates an off-station signal and transmits the off-station signal to the base station as off-station information based on the wireless communication link, wherein the off-station signal is used for indicating that the cleaning machine has left the base station.

Optionally, a charging contact is provided on the cleaning machine, a power supply contact is provided on the base station, and the charging contact is used for being electrically connected with the power supply contact to form a physical charging link.

Optionally, the base station determining that the cleaner leaves the base station according to the self current change specifically includes: the base station detects a second charging current output to the power supply contact; in the event that the second charging current is less than the second current threshold, the base station determines that the cleaning machine has left the base station.

Optionally, the impedance of the physical charging link formed when the charging contact and the power supply contact are electrically connected is greater than the impedance of either contact.

Optionally, the base station is further configured to: detecting a voltage at the power supply contact, wherein the voltage is inversely related to the impedance; and under the condition that the voltage is smaller than a preset voltage threshold value, determining that the cleaning machine is charged back in place, and charging the cleaning machine through a physical charging link.

Optionally, before determining that the cleaning machine is in place, the base station is further configured to: an infrared signal is emitted to guide the cleaner to dock with the base station through the infrared signal.

Optionally, the cleaning machine is further configured to: when the cleaning machine is charged in the non-reserved cleaning mode, the cleaning machine detects the electric quantity of the battery pack; when the battery pack is charged to saturation, the cleaner sends a charging stopping signal to the base station so that the base station stops outputting charging voltage; when the residual electric quantity of the battery pack is smaller than or equal to the first electric quantity threshold value, the cleaning machine sends a charging starting signal to the base station so that the base station starts outputting charging voltage until the battery pack is charged to saturation.

Optionally, the cleaning machine is further configured to: when the cleaning machine is charged in the reserved cleaning mode, the cleaning machine detects the electric quantity of the battery pack and determines the residual duration of the current moment from the reserved working moment; when the remaining time length is greater than a preset time length threshold and the charging capacity of the battery pack reaches a second electric capacity threshold, the cleaner sends a charging stopping signal to the base station so that the base station stops outputting the charging voltage; and when the residual duration reaches a preset duration threshold, the cleaner sends a charging starting signal to the base station so that the base station starts outputting charging voltage until the battery pack is charged to saturation.

Compared with the related art, the technical scheme provided by the embodiment of the application has the following advantages:

The technical scheme of the application provides a cleaning system, which comprises: a cleaner and a base station interfacing with the cleaner; the cleaning machine is used for sending the self-outbound information to the base station; and the base station is used for stopping outputting the charging voltage when receiving the off-station information or stopping outputting the charging voltage when determining that the cleaning machine leaves the base station according to the change of the current of the base station, wherein the charging voltage is used for charging the cleaning machine. The application can determine whether the cleaning machine leaves the base station from the cleaning machine side or from the base station side, and the base station can stop outputting the charging voltage under the condition that the cleaning machine leaves the base station, thereby saving electric energy, effectively eliminating potential safety hazards and solving the technical problems of resource waste and potential safety hazards caused by the fact that the base station outputs the charging voltage frequently.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described, and it will be apparent to those skilled in the art that other drawings can be obtained according to these drawings without inventive effort.

FIG. 1 is a schematic diagram of an alternative cleaning system provided in accordance with an embodiment of the present application;

FIG. 2 is a schematic diagram of yet another alternative cleaning system provided in accordance with an embodiment of the present application;

fig. 3 is a schematic diagram of yet another alternative cleaning system provided in accordance with an embodiment of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

In the following description, suffixes such as "module", "component", or "unit" for representing elements are used only for facilitating the description of the present application, and are not of specific significance per se. Thus, "module" and "component" may be used in combination.

In the related art, the method for realizing the charging function of the cleaning machine on the base station and the cleaning machine matched product is that the base station always outputs charging voltage, namely, when the cleaning machine is cleaned out of the base station, the charging port of the base station still keeps outputting the charging voltage. The constant output method not only wastes a large amount of electric energy resources, but also has certain potential safety hazards, such as short circuit risks when a small pet enters a charging port in a base station or wears a conductive chain when the cleaner is not in the base station.

To solve the problems mentioned in the background, according to an aspect of the embodiments of the present application, there is provided a cleaning system, as shown in fig. 1, including: a cleaning machine 100 and a base station 200 interfacing with the cleaning machine 100; a cleaner 100 for transmitting its own departure information to the base station 200; the base station 200 is used for stopping outputting the charging voltage when receiving the off-station information, or stopping outputting the charging voltage when determining that the cleaner leaves the base station according to the change of the current of the base station, wherein the charging voltage is used for charging the cleaner.

In the embodiment of the application, the cleaning machine can be a floor sweeping machine, a floor mopping machine, a floor sweeping and mopping integrated machine and the like. The base station is a station for providing the cleaning machine with functions of charging, water supplementing, garbage recycling, stopping for standby and the like. The cleaner can be in butt joint with the base station through infrared signals, for example, an infrared emitting device is arranged on the base station to emit infrared beams outwards, and an infrared receiving device is arranged on the cleaner to find an alignment position according to the received infrared signals, so that the cleaner enters the alignment position to finish the butt joint with the base station. In addition, the laser beam can be emitted outwards by laser docking, for example, a laser emitting device is arranged on a base station, and a laser receiving device is arranged on the cleaner so as to find the alignment position according to the received laser signal. The cleaning machine and the base station can be respectively provided with an electric contact or a signal contact for docking so as to form a physical charging link, for example, the cleaning machine is provided with a charging contact, the base station is provided with a power supply contact, and when docking is completed, the charging contact is in contact with the power supply contact to be electrically connected so as to form a charging loop, and accordingly the base station can charge the cleaning machine.

In the embodiment of the application, the core ideas are that the base station judges whether the cleaning machine leaves the base station or not, namely, stops outputting the charging voltage, the first judging means is completed by the base station, the base station detects the change of the self current to determine whether the cleaning machine leaves the base station, the second judging means is completed by the cleaning machine, the cleaning machine detects the change of the self current to judge whether the cleaning machine leaves the base station or not, and then the base station is informed of the leaving information to help the base station to make charging decisions.

In the related art, due to the adoption of a working mode of constantly outputting charging voltage, a large amount of electric energy resources are wasted, and even certain potential safety hazards exist. According to the technical scheme, whether the cleaning machine leaves the base station or not can be determined from the cleaning machine side or the base station side, and then the base station can stop outputting the charging voltage under the condition that the cleaning machine leaves the base station is determined, so that electric energy is saved, potential safety hazards can be effectively eliminated, and the technical problems that resources are wasted and potential safety hazards exist due to the fact that the base station outputs the charging voltage frequently are solved.

The scheme of determining the departure information by the cleaning machine itself and transmitting the departure information to the base station by the cleaning machine will be described in detail.

Alternatively, as shown in fig. 2, the cleaning machine 100 includes a battery pack 110 and a first communication module 120, the base station 200 includes a second communication module 210, the battery pack 110 is used to store electric energy, and the first communication module 120 and the second communication module 210 are used to establish a wireless communication link 300 between the cleaning machine 100 and the base station 200.

In the embodiment of the application, the first communication module and the second communication module are arranged to enable wireless communication between the cleaner and the base station, so that the first communication module and the second communication module can be any communication equipment with the capability of building a wireless communication link, and can be 433Mhz wireless communication module of Sub 1G, bluetooth, wiFi and the like in consideration of the applicability to the cleaner and the base station.

Based on the above-mentioned wireless communication link constructed between the cleaning machine and the base station, the cleaning machine transmits its own departure information to the base station specifically includes: detecting a first charging current of the battery pack by the cleaner; in the case that the first charging current is less than the first current threshold, the cleaning machine generates an off-station signal and transmits the off-station signal to the base station as off-station information based on the wireless communication link, wherein the off-station signal is used for indicating that the cleaning machine has left the base station.

In the embodiment of the application, the cleaning machine can detect the first charging current of the battery pack to judge whether the cleaning machine leaves the base station or not, when the base station continuously charges the battery pack, the first charging current of the battery pack is kept at a larger and stable level, when the cleaning machine leaves the base station, the first charging current is suddenly reduced because no electric energy is input, so that an off-station signal of the cleaning machine leaving the base station can be obtained, and finally, the cleaning machine can send the off-station signal to the base station as the off-station information through the wireless communication link, so that the base station can determine that the cleaning machine leaves the base station when receiving the off-station signal, and further, the output of the charging voltage is stopped. The first current threshold may be determined according to the actual hardware characteristics of the cleaning machine and the base station, or may be set according to actual needs, and preferably, the first current threshold may be 20mA.

The scheme of determining the second state change information by the base station side will be described in detail.

Optionally, as shown in fig. 3, a charging contact 130 is provided on the cleaning machine 100, a power supply contact 220 is provided on the base station 200, and the charging contact 130 is configured to electrically connect with the power supply contact 220 to form a physical charging link 400.

In the embodiment of the application, each contact is plated with nickel to prevent rust and oxidation. The number of charging contacts and power supply contacts is at least one, each pair implementing the physical charging link.

Based on the above-mentioned physical charging link constructed between the cleaning machine and the base station, the base station determines that the cleaning machine leaves the base station according to the self current change specifically includes: the base station detects a second charging current output to the power supply contact; in the event that the second charging current is less than the second current threshold, the base station determines that the cleaning machine has left the base station.

In the embodiment of the application, the base station can detect the second charging current output by the base station to the power supply contact to judge whether the cleaner leaves the base station, when the base station continuously charges the battery pack of the cleaner, the second charging current is kept at a large and stable level, and when the cleaner leaves the base station, the second charging current is suddenly reduced because no load receives electric energy, and the base station can determine that the cleaner leaves the base station according to the second charging current.

Since the operation state of the cleaning machine is not just away from the base station, the cleaning machine will be described below as an example of the need for recharging.

In the embodiment of the application, when the base station detects that the cleaning machine is charged back in place, the charging function is started to transmit electric energy to the cleaning machine. The base station detects whether the cleaning machine is charged back in place or not and can judge by detecting the voltage at the power supply contact, specifically, the base station detects the voltage at the power supply contact, wherein the voltage is inversely related to the impedance; it can be understood that when the charging contact is electrically connected with the power supply contact, the impedance of the formed physical charging link is larger than the impedance of any contact, so when the charging contact is electrically connected with the power supply contact to form the physical charging link, the total impedance is larger than the single impedance of the power supply contact, the change of the impedance causes the change of the voltage at the power supply contact, and the change relationship is a negative correlation relationship, therefore, when the base station detects that the voltage at the power supply contact is smaller, the base station judges that the cleaner is charged back into place, and can start charging the cleaner, namely: and under the condition that the voltage is smaller than a preset voltage threshold value, determining that the cleaning machine is charged back in place, and charging the cleaning machine through a physical charging link.

The technical scheme that the operation state of the cleaning machine can be determined from the side of the cleaning machine or from the side of the base station by taking the two operation states of the cleaning machine leaving the base station and the cleaning machine recharging as examples is described in detail, and then the base station can execute the charging strategy matched with the change condition of the operation state of the cleaning machine is provided, so that it can be understood that the charging strategy can be adaptively matched with other operation states of the cleaning machine, and the application is not repeated.

The embodiment of the application also provides a cleaning system capable of further saving energy, and particularly aims at a reserved cleaning mode and a non-reserved cleaning mode of the cleaning machine, and particularly, the cleaning machine detects the electric quantity of a battery pack when the cleaning machine is charged in the non-reserved cleaning mode; when the battery pack is charged to saturation, the cleaner sends a charging stopping signal to the base station so that the base station stops outputting charging voltage; when the residual electric quantity of the battery pack is smaller than or equal to the first electric quantity threshold value, the cleaning machine sends a charging starting signal to the base station so that the base station starts outputting charging voltage until the battery pack is charged to saturation. When the cleaning machine is charged in the reserved cleaning mode, the cleaning machine detects the electric quantity of the battery pack and determines the residual duration of the current moment from the reserved working moment; when the remaining time length is greater than a preset time length threshold and the charging capacity of the battery pack reaches a second electric capacity threshold, the cleaner sends a charging stopping signal to the base station so that the base station stops outputting the charging voltage; and when the residual duration reaches a preset duration threshold, the cleaner sends a charging starting signal to the base station so that the base station starts outputting charging voltage until the battery pack is charged to saturation.

In the embodiment of the application, the first electric quantity threshold and the second electric quantity threshold can be set according to actual needs, wherein the first electric quantity threshold is selected by taking energy conservation into consideration, the service life of the battery pack is also considered, and the second electric quantity threshold is selected by taking energy conservation into consideration, and is also ensured to be not lower than the minimum electric quantity required by executing a cleaning task. Preferably, the first power threshold value and the second power threshold value may be set to 60% of the saturated power. In this way, in the non-reserved cleaning mode, when the battery pack capacity of the cleaner is 100%, the base station is triggered to turn off the charging enabling function until the battery pack capacity is lower than 60%, and the charging function is enabled again, so that the cycle is performed. In the reserved cleaning mode, after cleaning all rooms each time, the cleaning machine returns to the base station to perform deep self-cleaning, when the next reserved time is reached, the cleaning machine triggers the work, and the cleaning machine is charged to about 60%, the stage is the optimal electric quantity preservation stage of the battery, and in order to ensure that the next reserved start is high electric quantity, the charging function is started before the work of the work sweeper is triggered, for example, a user reserves 5 pm every day: 00 starts cleaning, 4 pm: the 00 base station actively starts the charging function, and the service life of the battery pack of the sweeper is prolonged on the basis of energy conservation.

According to the technical scheme, the running state of the cleaning machine can be determined from one side of the cleaning machine or from one side of the base station, so that the base station can execute a charging strategy matched with the change condition of the running state of the cleaning machine, the time and the magnitude of the output charging voltage can be controlled, electric energy is saved, potential safety hazards can be effectively eliminated, and the technical problems that resources are wasted and potential safety hazards exist due to the fact that the base station frequently outputs the charging voltage are solved.

It is to be understood that the embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or a combination thereof. For a hardware implementation, the Processing units may be implemented within one or more Application SPECIFIC INTEGRATED Circuits (ASICs), digital signal processors (DIGITAL SIGNAL Processing, DSPs), digital signal Processing devices (DSP DEVICE, DSPD), programmable logic devices (Programmable Logic Device, PLDs), field-Programmable gate arrays (Field-Programmable GATE ARRAY, FPGA), general purpose processors, controllers, micro-controllers, microprocessors, other electronic units for performing the functions described herein, or a combination thereof.

For a software implementation, the techniques described herein may be implemented by means of units that perform the functions described herein. The software codes may be stored in a memory and executed by a processor. The memory may be implemented within the processor or external to the processor.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, and are not repeated herein.

In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, and for example, the division of the modules is merely a logical function division, and there may be additional divisions when actually implemented, for example, multiple modules or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in the embodiments of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the embodiments of the present application may be embodied in essence or a part contributing to the prior art or a part of the technical solution, in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present application. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk, etc. It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1.A cleaning system, comprising:

A cleaning machine and a base station interfacing with the cleaning machine;

the cleaning machine is used for sending the self-outbound information to the base station;

The base station is used for stopping outputting the charging voltage when receiving the off-station information or stopping outputting the charging voltage when determining that the cleaning machine leaves the base station according to the change of the current of the base station, wherein the charging voltage is used for charging the cleaning machine.

2. The system of claim 1, wherein the system further comprises a controller configured to control the controller,

The cleaning machine comprises a battery pack and a first communication module, the base station comprises a second communication module, the battery pack is used for storing electric energy, and the first communication module and the second communication module are used for establishing a wireless communication link between the cleaning machine and the base station.

3. The system according to claim 2, wherein the cleaning machine transmits its own departure information to the base station specifically comprises:

the cleaning machine detects a first charging current of the battery pack;

The cleaning machine generates an off-station signal and sends the off-station signal to the base station as the off-station information based on the wireless communication link, where the off-station signal is used to indicate that the cleaning machine has left the base station, if the first charging current is less than a first current threshold.

4. The system of claim 1, wherein the system further comprises a controller configured to control the controller,

The cleaning machine is provided with a charging contact, the base station is provided with a power supply contact, and the charging contact is used for being electrically connected with the power supply contact to form a physical charging link.

5. The system of claim 4, wherein the base station determining that the cleaner is leaving the base station based on the change in the self current comprises:

The base station detects a second charging current output to the power supply contact;

In the event that the second charging current is less than a second current threshold, the base station determines that the cleaning machine has left the base station.

6. The system of claim 4, wherein the system further comprises a controller configured to control the controller,

When the charging contact and the power supply contact are electrically connected, the impedance of the formed physical charging link is larger than the impedance of any contact.

7. The system of claim 6, wherein the base station is further configured to:

detecting a voltage at the power supply contact, wherein the voltage is inversely related to the impedance;

and under the condition that the voltage is smaller than a preset voltage threshold, determining that the cleaning machine is charged back in place, and charging the cleaning machine through the physical charging link.

8. The system of claim 7, wherein prior to determining that the cleaning machine is recharging in place, the base station is further configured to:

an infrared signal is emitted to guide the cleaner to dock with the base station through the infrared signal.

9. The system of claim 1, wherein the cleaning machine is further configured to:

when the cleaning machine is charged in the non-reserved cleaning mode, the cleaning machine detects the electric quantity of the battery pack;

When the battery pack is charged to be saturated, the cleaner sends a charging stopping signal to the base station so as to stop the base station from outputting charging voltage;

And when the residual electric quantity of the battery pack is smaller than or equal to a first electric quantity threshold value, the cleaning machine sends a charging starting signal to the base station so that the base station starts to output charging voltage until the battery pack is charged to saturation.

10. The system of claim 1, wherein the cleaning machine is further configured to:

when the cleaning machine is charged in the reserved cleaning mode, the cleaning machine detects the electric quantity of the battery pack and determines the residual duration of the current moment from the reserved working moment;

When the remaining time length is greater than a preset time length threshold value and the charging electric quantity of the battery pack reaches a second electric quantity threshold value, the cleaner sends a charging stopping signal to the base station so that the base station stops outputting charging voltage;

And when the residual duration reaches the preset duration threshold, the cleaning machine sends a charging starting signal to the base station so that the base station starts to output charging voltage until the battery pack is charged to saturation.