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PB251A -CM Series PB251A -CM - Battery Charger System

  • 220 - 330W Battery Charger System
  • DC UPS Connectable
  • Constant Float Voltage & Current Limit
  • Independent Battery Charging Output
  • DC OK & Battery OK Alarms with Relays
  • Battery Connected Test
  • Battery Low Volts Disconnect
  • Optional Battery Charge Current Limit
  • Optional Network Connected
  • Optional Battery Temperature Probe

PB251A  -CM - Battery Charger System

Product Overview


PB251A Series Battery Chargers / DC UPS

The PB251A Series is a family of 13.8Vdc and 27.6Vdc 275W/330W off-line battery chargers / DC uninterruptible power supplies, which operate from 220/240Vac mains power.  When connected to a lead-acid battery, these units provide uninterrupted power to a DC load in the event of a mains failure.

The PB251A contains a two step current limited float charger, battery charge current limiting, a battery low voltage disconnect, mains/charger and battery alarms, battery present detection and optional float voltage temperature compensation (option -T).  It employs high efficiency switching technology, combined with  very low output noise which makes it suitable for powering sensitive loads such as radio equipment.

The PB251A is available in chassis mount (CM) and 2RU 19" rack mount (RML and B) variants.  A supplementary heatsink (option - H) is available to increase the output power or maximum ambient termperature rating of the chassis mount variant.  All models employ natural convection cooling.

The rack mount (RML and B) variants incorporate an alphanumeric LCD display as standard.  These variants are also available with analogue meters (option -M)


Input Voltage: 190 to 264Vac, or 225 to 400Vdc
Frequency: 45 to 65 Hz
Input Current: 1.4A maximum
Inrush current: 10A maximum
Line regulation: 0.2%typical
Output Voltage 13.8Vdc, 27.6Vdc
Output Current

13.8Vdc: 20A

27.6Vdc: 12A

Load regulation 0.5% typical
Ripple & noise
100 MHz bandwidth
28mVp-p (13.8Vdc output)
55mVp-p (27.6Vdc output)
Efficiency > 80%
Current limit

Load circuit - Constant current

Battery circuit - Constant current

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)

Input to Output: 4.2Kvdc 1 min

Output to Ground: 2.1Kvdc 1 min

Output to Ground: 700Vdc 1 min

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

Humidity 5 to 90% relative humidity (non-condensing)
Over-temperature protection Automatic & auto-resetting
Cooling requirement Natural convection
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
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

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
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
Battery Charge Current

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.

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

Conformal Coating Option CC: Tropic protection for moist areas
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










PB251A-12CM 13.8V 16A 2A 220W    
PB251A-12CM-H 13.8V 20A 4A 275W    
PB251A-24CM 27.6V 11A 2A 300W    
PB251A-24CM-H 27.6V 12A 2A 330W    

1). Total output current is sum of load and battery charging current.

2). Other optional BCL, Battery Charging Limit, available on request, factory set.

3). Example model number, PB251A-12CM-H-10   Includes Additional Heatsink and 10A battery charge current limit.

Technical Illustration

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