Powerbox PB251A-CM SERIES DC-UPS / Battery Charger
The Powerbox PB251A-CM Series DC-UPS and Battery Charger is a compact, high-reliability power solution designed to deliver up to 330W of continuous DC power with intelligent battery backup functionality. It supports critical infrastructure across a wide range of sectors with a focus on reliability, simplicity, and long-term serviceability. Engin...
Read MoreThe Powerbox PB251A-CM Series DC-UPS and Battery Charger is a compact, high-reliability power solution designed to deliver up to 330W of continuous DC power with intelligent battery backup functionality. It supports critical infrastructure across a wide range of sectors with a focus on reliability, simplicity, and long-term serviceability.
Engineered for electronic security and access control systems, the PB251A-CM is commonly deployed in field cabinets and secure enclosures, powering readers, locks, controllers, and supporting equipment. It is also a trusted solution for industrial automation applications, including extensive use within water utilities, where dependable DC power and backup capability are essential for telemetry, monitoring, and control equipment in remote or harsh environments.
Key features include constant float voltage, current limiting, and independent battery charging outputs with integrated battery low-voltage disconnect (LVD). LED indicators and alarm relays provide real-time DC and battery status, while optional features such as battery charge current limiting, SNMP V1-based network monitoring, and temperature compensation further enhance battery performance and system integration.
Available in 13.8Vdc (up to 20A) and 27.6Vdc (up to 12A) configurations, the PB251A-CM Series is convection-cooled and designed for dependable operation in a wide range of installation environments.
Fully compliant with AS/NZS60950 safety standards and C-Tick certified for EMC, the PB251A-CM Series is the trusted choice for compact, reliable DC-UPS installations across security, automation, and utility sectors.
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Features
- Compact, Intelligent DC-UPS: A space-efficient 220–330W system with true off-line DC-UPS functionality, delivering uninterrupted DC power by seamlessly switching to battery backup during mains failure. Built-in battery charging and management make it ideal for wall-mounted or enclosed control systems in security, automation, and utility applications.
- Trusted in Security and Industrial Environments: Widely used in electronic security, access control, and industrial automation systems—including applications within water utilities, where dependable power for monitoring and control infrastructure is essential.
- Built-In Battery Management: Includes constant float voltage, current limiting, a separate battery charging output, and integrated battery low-voltage disconnect (LVD) for full protection and backup continuity.
- Alarm and Status Monitoring: Dual green LED indicators and voltage-free relay contacts monitor DC OK and Battery OK conditions, alerting users to power loss, battery disconnection, or low-voltage conditions.
- Flexible Installation and Environmental Protection: Multiple mounting centre options and pluggable terminal blocks support easy integration in tight enclosures. An optional conformal coating is available to protect internal electronics in moisture-prone or harsh environments.
- Optional Enhancements for System Integration: Supports SNMP V1 network monitoring (Option -N), battery charge current limiting (BCL), and temperature compensation via external probes—enabling tailored performance and remote visibility.
Specifications
| INPUT | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Input Voltage: | 190...264Vac, or 225...400Vdc | ||||||||||||||||||||||||||||||||||||||||||||||||
| Frequency: | 45 to 65 Hz | ||||||||||||||||||||||||||||||||||||||||||||||||
| Input Current: | 1.4A maximum | ||||||||||||||||||||||||||||||||||||||||||||||||
| Inrush current: | 10A maximum | ||||||||||||||||||||||||||||||||||||||||||||||||
| Line regulation: | 0.2%typical | ||||||||||||||||||||||||||||||||||||||||||||||||
| OUTPUT | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Output Voltage | 13.8Vdc, 27.6Vdc | ||||||||||||||||||||||||||||||||||||||||||||||||
| Output Current |
13.8Vdc: 16A / 20A (-H) |
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| Load regulation | 0.5% typical | ||||||||||||||||||||||||||||||||||||||||||||||||
| Ripple & noise 100 MHz bandwidth |
28mVp-p (13.8Vdc output) 55mVp-p (27.6Vdc output) |
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| Efficiency | > 80% | ||||||||||||||||||||||||||||||||||||||||||||||||
| PROTECTION | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Current limit |
Load circuit - Constant current Battery circuit - Constant current |
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| Short circuit protection | Indefinite, auto-resetting | ||||||||||||||||||||||||||||||||||||||||||||||||
| Over-voltage protection | 17.5 to 20V latching (13.8Vdc output) 31.5 to 39V latching (27.6Vdc output) |
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| Isolation |
Input to Output: 4.2Kvdc 1 min Output to Ground: 2.1Kvdc 1 min Output to Ground: 700Vdc 1 min |
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| ENVIRONMENTAL | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Operating temperature |
0 to 70°C ambient Derating from full power at Ta = 25°C to 0W at Ta=70°C at -2.22%/°C |
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| Humidity | 5 to 90% relative humidity (non-condensing) | ||||||||||||||||||||||||||||||||||||||||||||||||
| Over-temperature protection | Automatic & auto-resetting | ||||||||||||||||||||||||||||||||||||||||||||||||
| Cooling requirement | Natural convection | ||||||||||||||||||||||||||||||||||||||||||||||||
| STANDARDS & APPROVALS | |
|---|---|
| C-Tick | AS/NZS CISPR11 Group 1 Class A. |
| Safety | Complies with AS/NZS 60950, class 1, NSW Office of Fair Trading Approval N20602 |
| EMC | Emissions comply with AS/NZS CISPR11,Group 1, Class B. Complies with ACA EMC Scheme,Safety & EMC Regulatory Compliance Marked |
| ALARMS & BATTERY FUNCTIONS | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DC OK alarm | Green LED : ON=OK voltage free change over relay contacts (32V,1A) Alarms on loss of AC mains power or failure of off-line AC/DC converter / battery charger | ||||||||||||||||||||||||||||||||||||||||||||||||
| Battery OK alarm | Green LED : ON=OK voltage free change over relay contacts(32V,1A) Alarms on battery low voltage 11V, failure of battery fuse or battery disconnected. Alarm cancelled when fuse or battery replaced, or AC input restored | ||||||||||||||||||||||||||||||||||||||||||||||||
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Battery low voltage disconnect (LVD) |
10.2 to 12.6V for 12V battery, adjustable 20.4 to 25.2V for 24V battery,adjustable Indicated by voltage-free changeover relay contacts & green LED: ON=BATT OK | ||||||||||||||||||||||||||||||||||||||||||||||||
| Low voltage disconnect | 9.6 to 12V for 12V battery, adjustable 19.2 to 24V for 24V battery, adjustable |
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| Charger over-load protection | Auto-resetting electronic circuit breaker | ||||||||||||||||||||||||||||||||||||||||||||||||
| Reverse polarity protection | Internal battery fuse | ||||||||||||||||||||||||||||||||||||||||||||||||
| Battery to load voltage drop | 0.2 to. 0.25V typical | ||||||||||||||||||||||||||||||||||||||||||||||||
| OPTIONAL FEATURES | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Battery Charge Current Limit (BCL) |
Factory set to any value within adjustment the range. For the PB251A-12CM, battery charging current limit can be set from 2A to 20.5A . For the PB251A-24CM battery charging current limit can be set from 1A to 12.5A . Battery charging current option can be specified when ordering e.g. PB251A-12CM-10 for 10A setting. |
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| Heatsink | Option H: Supplementary heatsink | ||||||||||||||||||||||||||||||||||||||||||||||||
| Network enabled | Option N: Internal network card in conjunction with PB251A becomes a network enabled device combining the benefits of SNMP V1, XML and embedded webpage. | ||||||||||||||||||||||||||||||||||||||||||||||||
| Temperature compensation |
Option T: 2.5m cable probe Option T5: 5m cable probe Float voltage set to 2.3V/cell at 25°C with compensation of 3.3mv/°C cell |
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| Conformal Coating | Option CC: Tropic protection for moist areas | ||||||||||||||||||||||||||||||||||||||||||||||||
| MECHANICAL | |
|---|---|
| Input connector | IEC60320 inlet,10A Class 1 2 meter IEC mains cord with Australian plug is supplied with each unit |
| Output/Battery connector | 4 way pluggable screw terminal block Suitable for up to 4mm² wire |
| Alarm terminal | 6 way pluggable screw terminal block Suitable for up to 1.5mm² wire |
| Case size | 264 L x 172 W x 67 H mm |
| Case size with heatsink | 264 L x 186 W x 67 H mm |
| Weight | 1.9kg |
| Weight with heatsink | 2.1kg |
| Rack mount option | Refer to PB251-RM Series |
| Security Cabinet | View WMBB-C-S Security Cabinet |
Selection Table
| MODEL NUMBER | OUTPUT VOLTAGE | LOAD CURRENT | BATTERY CHARGE CURRENT ¹ | TOTAL CURRENT | OUTPUT POWER |
|---|---|---|---|---|---|
| PB251A-12CM | 13.8V | 14A | 2A | 16A | 220W |
| PB251A-12CM-H | 13.8V | 18A | 4A | 20A | 275W |
| PB251A-24CM | 27.6V | 9A | 2A | 11A | 300W |
| PB251A-24CM-H | 27.6V | 10A | 2A | 12A | 330W |
Notes:
¹ Other optional BCL, Battery Charging Limit, available on request (factory set).
² Example models number, PB251A-12CM-H-N-05 - Includes heat sink, network card and 5A battery charge current limit.
Technical Drawings
Warranty & Returns
Warranty periods vary by product. Please refer to the Powerbox Warranty Policy for the applicable coverage period against manufacturing defects from date of purchase. For returns and RMA requests, please visit our RMA support page or contact our support team directly.