WO2018233556A1

WO2018233556A1 - Power monitoring system, communication device

Info

Publication number: WO2018233556A1
Application number: PCT/CN2018/091431
Authority: WO
Inventors: 彭雪峰
Original assignee: 中兴通讯股份有限公司
Priority date: 2017-06-23
Filing date: 2018-06-15
Publication date: 2018-12-27
Also published as: CN109120058A

Abstract

Provided are a power monitoring system and a communication device. The power monitoring system comprises: a monitoring module (10) configured to monitor an alternate-current power supply state; a charging module (12), connected to a first battery and a second battery, configured to charge the first battery and the second battery; a power supply module (14), connected to the monitoring module (10), configured to enable the first battery and the second battery to supply power cyclically when the alternate-current power supply state indicates that the alternate-current power supply has been interrupted.

Description

Power monitoring system, communication equipment

Technical field

The present disclosure relates to the field of communications, and in particular, to a power monitoring system and a communication device.

Background technique

For a long time, in the communication energy equipment, lead-acid batteries have been configured as backup equipment to avoid the paralysis of communication systems caused by AC power outages. However, the lead-acid battery has a short cycle life, a shallow discharge depth, and a large volume, and there are certain drawbacks in use. In recent years, with the deepening of research on iron-lithium batteries, the advantages of iron-lithium batteries: long cycle life, high temperature performance, large capacity, no memory effect, light weight, environmental protection, etc. are more and more well-known, so iron in the field of communication energy The call for lithium batteries to replace lead-acid batteries is getting higher and higher.

However, due to the relatively high price of iron-lithium batteries, the same capacity is about 3-5 times that of lead-acid batteries. Therefore, in many application scenarios of communication energy, in order to reduce costs, a set of lead-acid batteries and a set of lithium-lithium batteries are configured. Energy storage equipment; in other scenarios, lead-acid batteries have been used for a certain period of time. In order to extend the life of lead-acid batteries and reduce the running time of the oil machine, a set of iron-lithium batteries will be incorporated into the old system, and the old lead-acid batteries will be used. As a backup for the iron-lithium battery, the iron-lithium battery is preferentially charged and discharged, and the lead-acid battery is periodically charged and discharged.

In the application of mixed power supply of lead-acid battery and iron-lithium battery, there are still many problems to be solved. For example, the characteristics of lead-acid battery and iron-lithium battery are different. When charging, the charging voltage and charging current are inconsistent, and the charging voltage of iron-lithium battery is different. 55V, and the lead-acid battery charging voltage is 56.4V, the current mixed battery charging voltage is taken as the charging voltage, such as 55.5V, the lithium-ion battery charging voltage is too high, it will cause the iron-lithium battery overcharge and damage, The long-term undercharge of lead-acid batteries will reduce their life due to their own memory effect; in discharge, the reasonable discharge DOD of iron-lithium batteries is 60%, while the lead-acid batteries are 40%. In the reasonable discharge range, the voltage of iron-lithium batteries The reduction is small, and the voltage change of the lead-acid battery is relatively large. At about 5V, the function of controlling the start and stop of the oil machine and disconnecting the electric equipment according to the battery voltage is difficult to realize. The current problem in the application is generally a lithium-lithium battery. Insufficient discharge, or insufficient discharge of lead-acid batteries, results in increased engine run time.

Summary of invention

The following is an overview of the topics detailed in this document. This Summary is not intended to limit the scope of the claims.

The present disclosure provides a power monitoring system and a communication device, which are related to the problem that the battery is not fully discharged and affects the performance of the battery and the power receiving unit.

According to an embodiment of the present disclosure, a power supply monitoring system includes: a monitoring module configured to monitor an AC power supply state; a charging module coupled to the first battery and the second battery, configured to be opposite to the first battery and The second battery is charged; the power supply module is connected to the monitoring module, and is configured to cyclically supply power using the first battery and the second battery when the AC power supply state indicates that the AC power supply is interrupted.

According to another embodiment of the present disclosure, there is provided a communication device comprising: a base station, an alternating current power source, a first battery, and a second battery, the device further comprising: the power source monitoring system in the above embodiment.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF abstract

1 is a block diagram showing the structure of a power supply monitoring system according to an embodiment of the present disclosure;

2 is a structural block diagram of a communication device in accordance with an embodiment of the present disclosure;

FIG. 3 is a diagram of a software module partition and a cooperation relationship of each module according to an embodiment of the present disclosure; FIG.

4 is a flow chart of control logic in a charging process according to an embodiment of the present disclosure;

FIG. 5 is a flow chart of control logic in a discharge process according to an embodiment of the present disclosure.

Detailed

The present disclosure will be described in detail below with reference to the drawings in conjunction with the embodiments.

The terms "first", "second" and the like in the specification and claims of the present disclosure and the above-mentioned figures are used to distinguish similar objects, and are not necessarily used to describe a particular order or order.

Example 1

As used hereinafter, the term "module" may implement a combination of software and/or hardware of a predetermined function. Although the devices described in the following embodiments are typically implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.

In this example, a power monitoring system is provided. FIG. 1 is a structural block diagram of a power monitoring system according to an embodiment of the present disclosure. As shown in FIG. 1, the method includes:

The monitoring module 10 is configured to monitor an AC power supply state;

The charging module 12 is connected to the first battery and the second battery and configured to charge the first battery and the second battery;

The power supply module 14 is connected to the monitoring module and configured to cyclically supply power using the first battery and the second battery when the AC power supply state indicates that the AC power supply is interrupted.

Through the system of the embodiment, during discharge, cyclic discharge, through the setting of the discharge relationship parameter, the two groups of batteries are fully involved in the cycle, the chemical activity of the two batteries can be maintained, the service life of the battery can be prolonged, and the battery discharge can be solved. Insufficient effects on the performance of the battery and the power receiving unit, but also greatly improve the utilization of the battery and reduce the cost of the battery.

In the embodiment, the first battery and the second battery may be any one of them, and may be any active and standby, unless otherwise specified.

In an embodiment, the charging module may further include: a common charging unit configured to simultaneously charge the first battery and the second battery; or, a separate charging unit configured to sequentially charge the first battery and the second battery.

In an exemplary embodiment according to the present embodiment, the system simultaneously charges two batteries, and the charging step of the common charging unit includes:

S11, comparing voltages of the first battery and the second battery to obtain a voltage difference, and turning on a charging circuit of the battery with a low voltage;

S12. When detecting that the voltage difference is less than a preset threshold, turning on a charging circuit of a battery that does not conduct the charging circuit.

In another exemplary embodiment according to the present embodiment, the system separately charges two batteries, and the charging step of the separate charging unit includes:

S21, turning on the charging circuit of the first battery, and charging the first battery according to the charging coefficient of the first battery;

S22, after the charging of the first battery is completed, switching the charging circuit to the second battery, and charging the second battery according to the charging coefficient of the second battery; wherein, the first battery is a main battery, and the second battery is a backup battery.

When charging separately, the charging voltage and charging current can be set differently according to the respective characteristics of the battery, so that the advantages of large current charging of the battery can be fully utilized, the charging efficiency can be improved, and a certain battery can be prevented from being overcharged, and in some special occasions, It is required to charge at the same time by setting the charging method.

In an embodiment, the power supply module may further include: a first switching unit configured to switch to the first battery for power supply when the AC power supply is interrupted; and the detecting unit configured to detect the real-time voltage and/or the depth of the first battery ( Depth of discharge (DOD); the second switching unit is configured to switch to the second battery for power supply when the DOD reaches the preset threshold. For example, the preset threshold value can be set to 60%, the preset voltage is 50V, when the DOD of the first battery reaches 60%, or (at the same time) the real-time voltage is less than 50V, switch to the second battery to continue to the power receiving unit. powered by.

In an embodiment, the detecting unit may further include: a calculating subunit configured to calculate a battery capacity (Amper/Hour, AH) discharged by the first battery during the discharging of the first battery, wherein the AH corresponds to the DOD. AH can be calculated by integrating the current with time.

In an exemplary embodiment according to the present embodiment, the second switching unit is further configured to switch to the second battery for power supply when the real-time voltage of the first battery is less than the preset voltage. The reserve energy of the first battery can be fully utilized.

In an embodiment, the power supply module may further include: a determining unit configured to determine a total number of discharges of the primary battery and the backup battery before the first switching unit switches to the first battery for power supply, in relation to the primary use When the discharge relationship parameter of the number of discharges of the battery and the number of discharges of the backup battery does not reach the preset threshold, determining that the primary battery is the first battery, the number of discharges in the primary battery and the backup battery When the discharge relationship parameter of the number of discharges reaches the preset threshold, it is determined that the backup battery is the first battery.

In this embodiment, the battery may be a lithium iron battery, a lead acid battery, or another type of battery, such as the first battery being a lithium iron battery and the second battery being a lead acid battery.

In this embodiment, a communication device is provided. FIG. 2 is a structural block diagram of a communication device according to an embodiment of the present disclosure. As shown in FIG. 2, the system includes: a base station 20, an AC power source 22, a first battery 24, and a second battery. 26. The power monitoring system 28, wherein the arrow indicates the power receiving direction, the base station 20 (which may be other powered devices) is the power receiving unit, and the AC power source 22 can charge the first battery 24 and the second battery 26 through the rectifier.

The above modules may be implemented by software or hardware. For the latter, the foregoing may be implemented by, but not limited to, the above modules are all located in the same processor; or, the above modules are respectively located in different combinations. In the processor.

Example 2

The present example is a detailed description of the present application in conjunction with the scenario and examples in accordance with the exemplary embodiments of the present disclosure:

The solution of the embodiment relates to a charging and discharging control strategy when a lead-acid battery and a lithium-lithium battery are mixed. When charging, the lead-acid battery and the iron-lithium battery use different charging currents; when discharging, the iron-lithium battery is selected according to the set conditions or Lead acid battery powered. It can solve the defects that the advantages of the iron-lithium battery can not be exerted when the lead-acid battery and the iron-lithium battery are mixed, and the service life of the lead-acid battery can be prolonged to some extent. Especially in some communication base stations that have been used for a certain period of time, lead-acid batteries have been aging. If the base station is retrofitted, iron-lithium batteries are added according to the capacity ratio, and this technology can better demonstrate its superiority.

In the charging process, if the lead-acid battery or the iron-lithium battery can be separately charged in the charging process, the charging voltage and the charging current are set according to the type of the battery, so that the problem of improper charging of the iron-lithium and the lead-acid battery can be avoided; During the discharge process, the two batteries are discharged separately. When a group of batteries is placed in a certain DOD and then switched to another group of batteries for discharge, when both sets of batteries are placed in a reasonable DOD, the oil machine is started, so that it can be avoided. Insufficient battery discharge increases the operating time of the oil machine

In this embodiment, a new control strategy is proposed for the problem found in the mixed scene of the communication power system, the iron-lithium battery and the lead-acid battery, and the two batteries are separately charged by different charging voltages and charging currents during charging, so as to ensure that the two batteries can be charged. Both batteries are fully charged; when discharging, the iron-lithium battery is preferentially supplied according to the set conditions, and the lithium-ion battery has a long cycle life, and the service life of the lead-acid battery can be effectively extended.

The solution of this embodiment includes: a new control strategy, based on a communication power monitoring system, mainly applied to a hybrid battery power supply scenario. The power monitoring system is responsible for managing the power supply part of the communication system, including rectifiers, batteries, oil machines, DC power distribution, AC power distribution, etc., as a guarantee for 48V DC power supply of communication equipment. The power monitoring system collects AC power status, battery information, and power consumption information of the communication device in the communication base station. As the energy storage device of the power system, the battery plays a key role in the whole system. The iron-lithium battery and the lead-acid battery have different charging and discharging characteristics. When the two batteries are powered at the same time, two kinds of batteries should be considered in the charging process. The platform voltage, while taking into account the full use of the energy storage of the two batteries during the discharge process. Therefore, the present disclosure proposes that when charging, the charging circuit is switched by the sub-device, the lithium-ion battery is charged first, the charging voltage and the charging current are based on the iron-lithium battery, and the lithium-ion battery is fully charged and then charged with the lead-acid battery, the charging voltage and the charging current. Lead acid is the standard; in the discharge process, the priority iron-lithium battery supplies power to the load, and the iron-lithium battery is placed in a certain SOC (remaining capacity of the battery) (parameter can be set) to switch the discharge circuit to the lead-acid battery, and then let the lead-acid battery Separate power supply, in order to ensure that both lead acid and lithium iron batteries can participate in the discharge cycle, the present disclosure proposes the concept of the cycle ratio, when the number of discharges of the iron-lithium battery and the lead-acid battery meets the cycle ratio, the lead-acid battery is preferentially discharged. The control method proposed in the present disclosure is believed to play a reference role in the hybrid battery application scenario.

The power monitoring system described above must have the following conditions: it can manage battery charging and discharging; it can control the switching of the battery circuit; various control parameters can be set.

The core idea of this embodiment is the charge and discharge control when the battery is mixed. First, the iron-lithium battery and the lead-acid battery are arbitrarily defined as a main battery or a backup battery. During the charging process, the battery is charged by the charging method by default. The main battery is charged first, and the battery is recharged. The main battery is charged according to the charging voltage and charging current of the main battery, and the main battery is charged to a certain extent (can pass Parameter setting), control the sub-device to switch the charging circuit, disconnect the main charging circuit, turn on the backup battery charging circuit, charge the backup battery according to the charging voltage and charging current set by the backup battery; when selecting to co-charge, first The battery with low charging voltage, when the voltage difference between the main and standby batteries is less than 2V, simultaneously turns on the charging circuit of the main and standby batteries, and simultaneously charges the main and standby batteries, and the charging current is limited according to the smaller value of the two; during the discharging process, according to the cycle ratio Select which battery preferentially supplies power to the load. When the battery pack is discharged to the set DOD (discharge depth), the control sub-device switches to another group of batteries to supply power separately. When all the batteries are discharged to the set DOD, the power supply is requested. Charge the battery.

The steps to achieve the charging of the hybrid battery of the present disclosure are as follows:

Set the system charging parameters as shown in Table 1:

Table 1

Depending on the charging method, two different charging methods can be selected;

(3) When the charging mode is co-charging, after the system has mains or other power supply, compare the main and standby battery voltages, the battery charging circuit with low conduction voltage, and charge the battery with low voltage; The battery voltage is within 2V, the charging circuit of the main and standby batteries is turned on, and the two groups of batteries are charged, and the charging current is set to a smaller value of the main charging limit point;

(4) When the charging mode is separately charged, the system first switches to the main battery to the charging circuit, and charges the main battery according to the set main battery charging coefficient. During the charging process, the battery current I< is filled with the reading current (main ). If the condition is met, the system switches the backup battery to the charging circuit and charges according to the set backup battery charging parameters until it is full.

In another aspect, the steps of achieving the discharge of the hybrid battery of the present disclosure during discharge are as follows:

Set the system discharge parameters as shown in Table 2:

Table 2

When the system is powered off, the battery starts to discharge. The system switches to the main battery discharge circuit through the subsystem, so that the main battery is separately powered. During the discharge process, the AH number of the battery is discharged according to the battery current and the time integral. The main battery is also judged. The voltage V0 < V main, if it is, then switch to the backup battery discharge, and the standby battery discharges the AH number C prepared by the backup battery according to the battery current versus time integration. Calculate, if C master>=DOD master, then the main battery effective discharge times Timer main plus 1, if C standby>=DOD backup, the backup battery effective discharge times Timer is added 1;

In some areas, the mains conditions are good, and the battery discharge time is not long. As long as the power of three discharges exceeds DOD/3, the number of effective discharges is also increased by one. For example: every time the mains power is cut off, the main battery is used to supply power to the load. The power of each discharge is less than the set DOD main, but greater than the DOD main/3. When the main battery accumulates 3 times, the discharge capacity meets the DOD. Main / 3 <= C main <DOD main, then the main battery's effective discharge times Timer main plus 1; Similarly, each time the backup battery is discharged, the discharged power is not up to the set DOD, but greater than DOD Standby /3, when the backup battery accumulates 3 times of discharge power, both of which satisfy the DOD backup/3<=C main <DOD backup, then the effective discharge frequency of the backup battery is increased by 1;

When the Timer main-Timer backup>=discharge relationship parameter is satisfied, the next time the AC power is cut off, the system switches to the backup battery discharge circuit through the sub-device, and the backup battery is given priority to supply power to the load. Similarly, the AH number C is released and the V1 is judged. <V standby, if the condition is met, the system switches to the main battery discharge circuit through the sub-device, so that the main battery supplies power to the load separately;

3 is a software module division and a cooperation relationship diagram of each module according to an embodiment of the present disclosure, including a timing module, a discharge management module, a charging management module, a time integration module, and a loop switching control, and the functions of the modules respectively correspond to the implementation in the above steps. step.

The implementation of the scheme is described in detail below with examples:

A company's production communication energy monitoring system uses a set of 48V200Ah iron-lithium batteries and a set of 48V600AH lead-acid batteries, according to the hybrid battery power management mode.

4 is a flow chart of control logic in a charging process according to an embodiment of the present disclosure, and the entire control logic step is described below with reference to the accompanying drawings, including:

The main battery is configured as a lithium-lithium battery, and the backup battery is a lead-acid battery;

Setting parameters: charging voltage (lithium) is 55.2V, charging current (lithium) is 0.7C, full-cut off current (lithium) is 0.08C, charging voltage (lead) is 56.4V, charging current (lead) is 0.15C;

Before charging, the iron-lithium battery is discharged to 40% SOC, and the lead acid is discharged to 60% SOC;

Close the AC air to charge the battery, first charge the iron-lithium battery, after the charging current is stable, periodically sample the battery current I, and compare the relationship between the battery current and the full-off current multiplied by the nominal capacity If of the lithium-lithium battery, if I <If, the control sub-device switches the charging circuit and switches to lead-acid battery charging.

FIG. 5 is a flow chart of control logic in a discharge process according to an embodiment of the present disclosure, and the steps of implementing the entire control logic are described below with reference to the accompanying drawings, including:

(1) Set each control parameter according to Table 3;

table 3

参数parameter	设定值Set value
有效放电阈值(锂)DODLiEffective discharge threshold (lithium) DODLi	60％60%
有效放电阈值(铅)DODPbEffective discharge threshold (lead) DODPb	40％40%
放电关系参数Discharge relationship parameter	2:12:1
放电切换电压(锂)VLiDischarge switching voltage (lithium) VLi	50V50V
放电切换电压(铅)VPbDischarge switching voltage (lead) VPb	47V47V

Oil machine starting voltage VG

46V

(2) Connect the 60A load in the system, disconnect the AC open, let the battery discharge, and discharge the iron-lithium battery first;

(3) Periodically sample the voltage of the iron-lithium battery V0, and compare V0 and VLi. If V0<VLi is repeated 5 times, the switching command is issued, and the battery is discharged to the lead-acid battery, otherwise the step (3) is repeated;

(4) After cutting the lead acid, immediately close the AC open, charge the battery, you can see that the effective discharge time of the iron lithium TimerLi plus 1, and the effective discharge number of lead acid TimerPb is still 0;

(5) Repeat steps (2) to (4), TimerLi=2, and TimerPb=0, satisfying the TimerLi-TimerPb>=discharge relationship parameter;

(6) Disconnect the AC open again, the system will switch to the lead-acid battery discharge circuit;

(7) periodically sampling the lead-acid battery voltage V1, and comparing V1 and VPb, if V1 < VPb for 5 consecutive times, issue a switching command, switch to the discharge circuit of the iron-lithium battery, otherwise repeat step (7);

(8) Periodically sample the iron-lithium battery voltage V0, and compare V0 and VG. If V0 < VG for 5 consecutive times, start the oil-generator start command and start the oil machine to charge the battery.

In the above steps (2), (3), (6), (7), (8), if the system has AC power, it will directly exit the judgment.

According to the embodiment, during charging, when charging separately, the charging voltage and the charging current can be set differently according to the respective characteristics of the battery, so that the advantages of the large current charging of the iron-lithium battery can be fully utilized, the charging efficiency can be improved, and a certain group can be avoided. The battery is overcharged, and in some special occasions, it is required to charge the lithium iron lead at the same time, which can be achieved by setting the charging mode. When discharging, the two sets of batteries can fully participate in the cycle by setting the discharge relationship parameter. The chemical activity of the two batteries can extend the life of the lead-acid battery, while also greatly improving the battery utilization and reducing the cost of the battery.

Through the system of the embodiment of the present disclosure, when discharging, through the setting of the discharge relationship parameter, the two groups of batteries are fully involved in the cycle, the chemical activity of the two batteries can be maintained, the service life of the battery can be prolonged, and the battery discharge is insufficient. The problem affecting the performance of the battery and the power receiving unit also greatly improves the utilization of the battery and reduces the battery cost.

Those of ordinary skill in the art will appreciate that all or some of the steps, systems, and functional blocks/units of the methods disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be composed of several physical The components work together. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer readable medium, which may include computer storage media (or non-transitory media) and communication media (or transitory media). As is well known to those of ordinary skill in the art, the term computer storage medium includes volatile and nonvolatile, implemented in any method or technology for storing information, such as computer readable instructions, data structures, program modules or other data. Sex, removable and non-removable media. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridge, magnetic tape, magnetic disk storage or other magnetic storage device, or may Any other medium used to store the desired information and that can be accessed by the computer. Moreover, it is well known to those skilled in the art that communication media typically includes computer readable instructions, data structures, program modules or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and can include any information delivery media. .

The above description is only exemplary embodiments of the present disclosure, and is not intended to limit the disclosure, and various changes and modifications may be made to the present disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the present disclosure are intended to be included within the scope of the present disclosure.

Claims

A power monitoring system includes:

The monitoring module (10) is configured to monitor an AC power supply state;

a charging module (12) connected to the first battery and the second battery, configured to charge the first battery and the second battery;

The power supply module (14) is connected to the monitoring module (10), and is configured to cyclically supply power using the first battery and the second battery when the AC power supply state indicates that the AC power supply is interrupted.
The system of claim 1 wherein said charging module (12) further comprises:

a common charging unit configured to simultaneously charge the first battery and the second battery; or

A separate charging unit is provided to sequentially charge the first battery and the second battery.
The system of claim 2 wherein said common charging unit is further configured to:

Comparing voltages of the first battery and the second battery to obtain a voltage difference, and turning on a charging circuit of a battery having a low voltage;

When it is detected that the voltage difference is less than a preset threshold, the charging loop of the battery that does not conduct the charging circuit is turned on.
The system of claim 2 wherein said separate charging unit is further configured to:

Turning on a charging circuit of the first battery, and charging the first battery according to a charging coefficient of the first battery;

After the charging of the first battery is completed, switching the charging circuit to the second battery, and charging the second battery according to a charging coefficient of the second battery;

Wherein, the first battery is a primary battery, and the second battery is a backup battery.
The system of claim 1 wherein said power supply module (14) further comprises:

a first switching unit configured to switch to the first battery for power supply when the AC power supply is interrupted;

a detecting unit configured to detect a discharge depth DOD of the first battery, or a real-time voltage, or a discharge depth DOD, and a real-time voltage;

The second switching unit is configured to switch to the second battery to supply power when the DOD of the first battery reaches a preset threshold.
The system of claim 5, wherein the detecting unit further comprises:

Calculating a subunit, configured to calculate a battery capacity AH discharged by the first battery during the discharging of the first battery, wherein the AH corresponds to the DOD.
The system of claim 5, wherein the second switching unit is further configured to switch to the second battery for powering when the real-time voltage of the first battery is less than a preset voltage.
The system of claim 5, wherein the power supply module (14) further comprises:

a determining unit, configured to determine a total number of discharges of the primary battery and the backup battery, and determining the primary when a discharge relationship parameter between the number of discharges of the primary battery and the number of discharges of the backup battery does not reach a preset threshold Using the battery as the first battery, when the discharge relationship parameter of the number of discharges of the primary battery and the number of discharges of the backup battery reaches the preset threshold, determining that the backup battery is the first battery .
The system of claim 1 wherein said first battery is a lithium iron battery and said second battery is a lead acid battery.
A communication device comprising: a base station (20), an alternating current power source (22), a first battery (24), and a second battery (26), wherein the device further comprises: any one of claims 1 to 9. The power monitoring system (28).