SR250HI – 250W DC UPS

No – Break ™ DC Uninterruptible Power Supply TECHNOLOGY

The New SR250HI 250 W power supply is designed to provide DC power to lead-acid batteries for critical backup applications. All the functionality and durability has been retained with a more modern and easier to understand range of products being developed. Form factor and connectivity remains the same, so they will fit into the slots occupied by the old range – the legend continues!

No-Break ™ DC UPS systems maximise the integrity of standby battery installations, whilst optimising the life and availability of back up batteries.  They are now available with Serial and Ethernet Communications options.

The No-Break ™ system is the ideal solution for:

  • Critical systems of 100W to 750W (and above using parallel operation)
  • Applications requiring continuous on-line monitoring of battery and charger status
  • Providing cost-effective management of your battery system investment

Other features include:

  • Ability to view power supply data remotely
  • Automatic or manually initiated battery condition testing to ensure availability of standby power
  • The battery condition test feature of the No-Break ™ DC system determines the condition of the back-up batteries and will provide an early warning of potential failure. This gives plant operators enough warning to replace the faulty batteries before they are required, like in the event of a mains power failure. Battery condition tests are mandatory on some fire alarm systems and are now commonly specified by consultants for critical industrial systems.


  • Security – Access Control
  • Industrial Processes Switching Protection
  • Radio Repeaters – Remote Sites


  • Separate outputs for load and battery.
  • Battery detection—regular battery presence and battery circuit integrity checks.
  • Battery deep discharge protection.
  • Power loss & battery system alarms
  • No transition switching to backup battery
  • Rugged design and construction for long life and challenging environments


  • American Input Voltage 110 VAC ( 88 – 135 VAC)
  • Fanless Option rated at 210W up to 50°C – CSR200 
  • Communication Port ( RS232 ASCII – SR485 – MODBUS RTU – SNMP, webpages)
  • Digital Input/Outputs: Customizable 3 digital inputs & 1 digital output.
  • Battery Condition Test : Option auto test enabled on start-up
  • Mounting: 19″ Rack Mount with V/I meter available, Wall mount
  • N+1 redundancy
  • Boost Charger
  • Conformal Coating for harsh environments


 ModelOutput (V) PSU Rated  (A)Charge Limit (A)Recomm. Load  (A)Peak load on power fail (A)


Output power250 W
Input Voltage180V – 264VAC 45-65Hz
Output Voltages12V, 24V, 30V, 36V, 48V
Voltage Adj. Range85% – 105% of Vout
Overcurrent protectionConstant current limit under overload and short circuit conditions
IsolationInput – earth – 2.5KVdc
Output – earth – 500Vdc
Efficiency> 85%
Operating temperature-20  to 50 °C ambient at full load
Humidity0 – 95% relative humidity non – condensing
LVDLow Voltage Disconnect
LED IndicationGreen: Batt OK
Green: Power OK
Red: Standby
Alarms RelayForm C contacts  30VDC,2A/110VDC,0.3A,125VAC, 0.5A
AUX (Activated by BCT)
POWER (main fails, PSU fails)
BATTERY (batt missing , batt low, BCT fail)
Temp. CompensationTemperature sensor on 1.7m lead with adhesive pad: -4mV/ °C / cell ± 10%
Battery Charge Current LimitCustomizable on request.
Reverse PolarityBattery reverse connection will open internal fuse (and produce alarm)
Battery MonitoringDetects for presence of battery on start up, then every 60 minutes when charge    current < 200mA
Battery Circuit ProtectionElectronic circuit breaker (ECB) operates under the following conditions:
– Low Battery Volts: Battery Voltage drops to 1.67V/cell
Overload: Max load must not exceed 110% of rated current. Peak loads must be connected to B+ & B– terminals. Not suitable for N+1 connection
Short Circuit:  <2ms, backed up by fuse
Standby ModeTurns off DC output of PSU & allows load to run off battery


Optional Input Voltage88 – 132 VAC
Communication Port· RS232 (ASCII)
· RS485 (ASCII)
· Modbus RTU
· SNMP, Webpages
Digital Inputs/OutputsCustomizable 3 Digital Inputs and 1 Digital Output
Battery Condition Test (BCT)Option auto test enabled on start-up
Mounting· Standalone
· 19”Rack Mount . Optional V/I meter for subrack : SR-Meter
· Wall Mount
Boost ChargerCustomizable feature on request.



SR Series Comms Downloads  


  •  Why is Helios Power Solutions SR No-Break ; DC charger recommended by consultants for critical applications?

Our No-Break ™ DC chargers have been designed for industrial use and have over twenty years of proven reliable operations.  In addition, the chargers have many outstanding features such as fault alarms, LED fault alarm codes, battery detection, low voltage disconnect circuitry, automatic battery condition testing, communication options and can be connected to the battery permanently due to the precise temperature-compensated voltage control.

  • Why should we use a SR No-Break; as opposed to a normal float charger?

The No-Break ™ DC UPS  has many features which a normal float charger does not, these including:

    • Precise alarm indication for mains or DC faults
    • Overcurrent protection on the battery circuit
    • Battery presence checking
    • Temperature-compensated charging
    • Low voltage disconnect circuitry to prevent deep discharge of the battery
    • Independent charge current limit
    • Automatic battery condition testing
  • Why don’t you use a boost charge on the SR No-Break unit?

Normally it is not necessary to have a boost on the No-Break ™ unit, as the power is on the system continuously and it is not that critical to restoring 100% of charge rapidly, as in the case of cyclic applications.  A boost charge voltage may damage the equipment which is permanently connected to a standby system.

  • Can I use the SR No-Break DC UPS without a battery?

No, the No-Break ™DC UPS is designed to operate with a battery connected and instability may result if there is no battery connected.  If you wanted to do this then it is advisable to use a standard two-terminal DC power supply SR250HL

  • Why is the battery negative separate from the load negative in the SR No-Break DC UPS?

This is done to implement two of the features of the No-Break ™ UPS/charger.  There is an “electronic circuit breaker” fitted between the battery negative and load negative terminals to provide the battery overcurrent protection.  The separate battery circuit also allows for independent control of the charging current when required.

  • Can I connect the battery directly to the load terminals when using SR No-Break DC UPS?

No, it would nullify all the features of using the No-Break ™DC design and provide false alarm signals from the relays.  If you wanted to do this, then it is advisable to use a standard two-terminal float charger, with or without alarms.

  • When does the SR No-Break system disconnect to protect deep discharge of the battery?

At approximately 1.67 volts per 2V (nominal) cell, so for a 12V system the disconnect voltage is set at 10V.

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