Backup Power Supply and DC Monitoring

 

DC Power Supplies

1.UPS

UPS(Uninterruptible Power Supply) is an emergency power supply device integrating power conversion, energy storage, and control functions. It is a complete power supply guarantee system consisting of a rectifier, inverter, storage battery, static switch, and control circuit.

It has two core functions:

1. When the mains power is normal, it filters grid interferences such as voltage fluctuations, surges, and harmonics, and outputs stable and pure power;
2. When the mains power is interrupted, it seamlessly switches to battery storage power supply (online UPS switching time < 10ms), ensuring that load equipment does not shut down and data is not lost.

Key Reminder: UPS ≠ a simple battery! The battery is only the "energy storage component" of the UPS, responsible solely for electrical energy storage; a complete UPS system requires the collaborative work of core modules such as rectification, inversion, and switching to achieve power supply guarantee functions.

2.HVDC

It outputs 240V/336V high-voltage DC power, and is an "efficient power supply system" specially designed for data centers and communication base stations (replacing traditional UPS).

3.DC Power Screen

A low-voltage DC power supply system (outputting 24V/48V/110V/220V DC), a dedicated cabinet mainly supplying power to "control, protection, and signal" equipment in the power system;

 

Main Application Scenarios:

1. Power Industry: Substation control circuits, circuit breaker operating power supplies;
2. Industry: Power supplies for protection devices in factory power distribution rooms;
3. Construction: Power supplies for power distribution control in high-rise buildings.

 

 

 

Q: Why are external monitoring devices still needed when most of these DC power supplies are equipped with a Battery Management System (BMS)?

Modern UPS, especially mid-to-high-end online UPS, are equipped with quite complete built-in Battery Management Systems (BMS) that can monitor key parameters such as voltage, internal resistance, and temperature.

However, in actual critical infrastructure (such as data centers, communication rooms, and hospitals), external independent battery monitoring devices are still standard configuration, even mandatory requirements. The reason is that the positioning, depth, reliability, and management dimensions of the two are completely different, and they are complementary rather than substitute relationships.

1. Monitoring Depth and Accuracy: From "Parameters" to "Status"

 

Built-in UPS Monitoring:

It can usually only monitor the "terminal voltage" and "total current" of the entire battery pack. For a battery pack composed of dozens or even hundreds of series-connected single cells, a normal overall voltage does not mean each cell is healthy. Slight deterioration of one cell (such as increased internal resistance and capacity attenuation) will be "covered up" by other good cells.Internal resistance measurement is usually estimated or periodic, with limited accuracy and real-time performance.

External Professional Monitoring Equipment:

Core Function: Monitor each individual battery cell. Collect the voltage, internal resistance, and temperature of each cell in real time with high precision.

Direct Fault Point Localization: It can accurately alarm "Battery No. 17 in Battery Rack No. 3 has abnormally increased internal resistance" instead of generally reporting "Battery pack fault". This is crucial for quick maintenance.

2. Independence and Reliability: Avoiding Blind Spots of "Self-Inspection and Self-Judgment"

 

Built-in UPS Monitoring:

It is a subsystem of the UPS system. If the main control board, communication module, or the power supply itself of the UPS fails, the battery monitoring function may also fail or report incorrect data.

External Monitoring Equipment:

Physical Independence: It has an independent power supply (usually directly taking power from the battery), sensors, and a processor.

Functional Independence: Even if the UPS host is completely down, the external monitoring system can still work continuously, recording the discharge curve and status of the battery, providing "black box"-like evidence for post-fault analysis. This provides a crucial "second opinion" and "last line of defense".

3. Functional Expandability: From "Monitoring" to "Management"

 

Built-in UPS Monitoring:

Its main goal is to "protect the stable operation of the UPS itself", with relatively fixed functions such as preventing overcharging and over-discharging.

External Professional Monitoring System:

Capacity Testing and Prediction: Combined with discharge data, it can more accurately calculate and predict the remaining capacity (SoH) and remaining power (SoC) of the battery, rather than simple voltage estimation.

Trend Analysis and Early Warning: By recording the internal resistance and voltage change trends of each battery cell over a long period of time, early warnings can be issued months before the complete deterioration of battery performance, realizing predictive maintenance and avoiding sudden failures.

Balanced Management: Advanced systems can perform more precise control over the charging and discharging processes, or prompt the need for manual battery balancing, extending the overall service life of the battery pack.

4. Centralized and Intelligent Management

 

Built-in UPS Monitoring:

Data is usually limited to the local machine and needs to be uploaded through the UPS's network interface. There may be issues of protocol compatibility or incomplete data when integrating into third-party network management software.

External Monitoring System:

Designed for Centralized Monitoring: It natively supports standard communication protocols (such as Modbus, SNMP, TCP/IP), and can easily aggregate data from hundreds of battery cabinets (which may correspond to multiple UPS) into a central monitoring platform.

Professional Analysis Software: It provides graphical interfaces, historical curves, report generation, custom alarm thresholds, maintenance work order management and other functions, and is a professional tool for asset management and life cycle management.

5. Compliance with Regulations and Standards

In many industries (such as finance, telecommunications, and power), relevant design and operation and maintenance specifications (such as TIA-942 data center standards and power maintenance procedures of various operators) clearly require monitoring the individual cell voltage and temperature of key battery packs to ensure the highest availability level (Tier level). Using professional external monitoring equipment is the most direct and reliable way to meet these mandatory requirements.

6. Addressing Complex Battery Architectures

For large data centers, batteries may be independent of the UPS and deployed in a dedicated battery room (battery energy storage system) to supply power to the entire microgrid or high-voltage DC system (HVDC). In this case, the battery system itself is an independent asset, which naturally requires an independent and more powerful monitoring system.

Conclusion: UPS's Self-Inspection is a "Bottom Line Guarantee", while External Monitoring is "Lean Management"

1. For a UPS in a home or small office, built-in monitoring is usually sufficient.
2. However, for systems carrying core businesses, data, or life safety (such as data centers, hospital operating rooms, and telecom core computer rooms), the storage battery is the last power lifeline. It is necessary to conduct "microsurgical" detailed monitoring through external, independent, and professional monitoring equipment to ensure that this lifeline can be activated 100% reliably in the darkest moment of grid collapse.

 

 

 

Which Parts of the DC System Need Monitoring?

 

1. System Insulation Status (Unique to DC Screens)

Regularly monitor the insulation status of the positive and negative poles to the ground, but some DC screens require AC intrusion monitoring function, which is not supported by our products currently.

Purpose: Prevent equipment damage due to short circuits, prevent false tripping of circuit breakers, prevent maloperation of protection devices, and prevent refusal of protection actions.

 

2. Health Status of the Battery Pack and Ambient Temperature (Battery Room) (Lead-Acid Battery Monitoring)

 

3. Bus Voltage and Current (DC Power Meter)

Voltage Monitoring: Prevent overcharging and over-discharging of the storage battery.

Current Monitoring: Identify load mutations and internal faults (impact current generated by circuit breaker closing, short circuits).

 

 

 

Acrel Products

1. Battery Monitoring(Learn More,click here,Jump to Lead-acid Battery Monitoring solution page)

(1)A single battery pack is connected to the Acrel gateway, and then connected to the Acrel BMS platform + local HMI display topology diagram

(2)Multiple battery groups local HMI display + access to third-party BMS system

Model 1: ABAT100-HS Data Collector

-Application: Support collecting data from up to 120 pcs battery cell monitor and further upstream data via RS485 [MODBUS-RTU]; analysing remaining battery capacity [SOC, SOH]. -Upstream Methods: RS485 [MODBUS-RTU protocol] -Downsteam Methods: RJ12 (Self-defined protocol) -Power Supply: 24Vdc -Certificate&Standard: CE        Learn More +

Model 2: ABAT100-C Group Cell Current Monitor

-Application: Monitor charge&discharge current data of one group of battery; moniotr ambient temperature. -Measuring Current Range: Max 1000A AC -Measuring Temperature Range: -5℃～+105℃ -Accuracy: ±1% [Current]; ±1°C [Ambinet temperature] -Upstream Methods: RJ12 (Self-defined protocol) -Power Supply: 24Vdc -Certificate&Standard: CE Learn More +

Model 3: ABAT100-S Single-cell Monitor

-Application: Monitor inner resistance, voltage, negative pole           temperature of single cell. -Supported battery type: 2Vdc, 6Vdc, 12Vdc lead acid battery[Capacity less than 3000AH] -Measurement Range: 2&6&12Vdc [Voltage]; 50～65535uΩ [Inner resistance]; -5℃～+105℃ [Temperature] -Accuracy: ±0.1% [Voltage]; 1uΩ [Inner resistance resolution]; ±1°C [Temperature] -Upstream Methods: RJ12 (Self-defined protocol) -Power Supply: From monitoring single cell -Certificate&Standard: CE Learn More +

Model 4: ATP007kT Series Smart Touch Screen

-Application: Display and alarm real-time battery data from cell monitor. [Support up to 6 pcs ABAT100-HS data collector]       all AMC100 series Energy Meter -Communications: 2-channel RS485 [MODBUS-RTUprotocol]; 1-channel RJ45/Ethernet [MODBUS-TCP] -Size: 7 inches -Power Supply: 24Vdc              -Certificate&Standard: CE

Model 5: AHKC-EKC Split-core Hall Sensor

-Application: Paired with ABAT100-C for current input                      -Current Input Range: 0~(500~1500)A DC -Current Output Range: ±5Vdc -Aperture: φ55.5mm -Auxiliary Power Supply: ±12~±15Vdc -Advantage: Safety with electricity isolation Learn More +

 

2. DC Power Meters

 

Summarize

 

Core Points Review:

1. UPS is a complete power supply system, not just a simple battery. Its core value is "uninterrupted power supply + stable power supply";
2. Understand DC power supply systems such as HVDC and DC Power Screens;
3. High-demand customers are concentrated in industries such as power, medical care, data centers, and communications. The industry characteristics are continuous and reliable power supply, and needs should be explored in combination with policy mandatory requirements;
4. Acrel's solutions focus on lead-acid battery monitoring and DC side monitoring, with core advantages of compliance adaptation, accurate early warning, and intelligent operation and maintenance.

 

For more solutions and product details, please add my WhatsApp: +86 15076062079 for consultation,

or you can contact me by email: binn@acrel-electric.com