SR500L  – SR750L  Series

500W & 750W Standby Float Charger for Lead Acid Batteries

The SRL models are designed for use as a precision AC to DC power supply, or a float charger for lead acid batteries. Note that for float charging the output voltage must be set to approximately 15% above the nominal battery voltage. The SRL series can have an optional ethernet, RS485 or RS232 communications port fitted.


  • Industrial quality AC/DC power supply
  • Standalone – benchtop or fixed mounting
  • Front panel controls & indication
  • Suitable for float charging of lead-acid batteries
  • Suitable for parallel operation
  • Conservative design for long life
  • Precise voltage and current control

Optional Features

  • American Input Voltage 110VAC ( 88 – 135VAC)
  • Communication Port ( RS232 ASCII – SR485 – MODBUS RTU  – SNMP , webpages)
  • Mounting:  Rack Mount 19″ with V/I meter available, Wall mount
  • N+1 redundancy
  • Boost Charger
  • Optional temperature compensation for charging
  • Optional relay alarm outputs
  • Optional DC input


DC Power Supply Manufactures - DC UPS


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

Accessories Supplied

  • Mounting feet together with screws
  • AC power cord 1.5m with IEC320 socket and NZ/Aust plug
  • Mating screw-terminal plug for alarm outputs
  • Crimp lugs for stud terminal versions
  • DC screw terminal plug-in connector for ‘X’ version


 ModelOutput (V) Output (A)Power (W)
SR500L1213.836.2 (41.6 @ 12V)500
SR750L1213.836.2 (41.6 @ 12V)750


Input180V – 264V ( 88V-132VAC option)
FusingInternal AC input fuse
Overcurrent protectionConstant current limit under overload and short circuit conditions (except DC input versions which have primary current limit)
Isolation1KV DC input – output / earth
Efficiency> 85%
Hold-up time15 – 20 ms without batery
AlarmsMains fail (or PSU in standby mode)
DC low (Battery low or PSU low) – set at 92% of nominal voltage.
DC high
Alarm  relay contactsC – NO – NC changeover rated 1A /50V DC, 32VAC
AC Input ConnectorIEC320 inlet socket
CommsChoice of RS485 ,RS232, Ethernet
ProtocolsSNMP v1 or Modbus (external converter)
Dimensions146.5 W x 62 H  x 177 D mm (SR100L) , 150W x 61H x 242D (SR250L)
Weight0.94Kg (SR100L) , 1.7Kg(SR250L)
Operating temperature0 – 50 °C ambient at full load De-rate linearly >50 °C to no load @ 70 °C
Storage temperature -10 to 85 °C ambient
Humidity0 – 95% relative humidity non-condensing
CoolingFan cooled
EmiTo CISPR 22 / EN55022 class A
SafetyTo IEC950 / EN60950 / AS/NZS3260

IE ASCII to Modbus RTU converter

  • +PROTOCONMB protocol converter is designed to be used with No-BreakTM DC power supplies, with single battery output, for example, SR100i or SR250i with RS485 communication port. It enables the
    user to monitor and control in real time various power supply parameters using Modbus RTU protocol via the RS485 output port or the RS232 programming port.

IE ASCII to Modbus RTU converter +PROTOCONMB


  • The +PROTOCONMB-OE converter, in addition to the above, enables the user to monitor and control the power supply via Modbus TCP and HTTP over Ethernet. For further information on this version please refer to the +PROTOCONMB-x-OE data sheet.

IE ASCII to Modbus RTU converter +PROTOCONMB-OE


Custom Solutions

CAB364 is a 500W 24VDC battery charging system in a 6U 19 inch wall mount cabinet.

CAB364 is a 500W 24VDC battery charging system in a 6U 19 inch wall mount cabinet.The system comprises of one SR500L24FSL in 2U 19” sub-racks with a 50A decoupling diode for protection. The system is set to provide 27.2VDC at the output of the decoupling diode to float charge the batteries and provide the load. The output voltage is front adjustable with a pot mounted on the front panel of the charger. Relay contacts on the SR500L24FSL provide alarms for main/PSU fail, DC low set at 24.5VDC and DC high which is set at 28.5VDC.

A 3U distribution panel houses one 6A mains input MCB. The distribution panel also contains one 32A two-pole charger output MCB, one 32A single pole battery MCB and a 32A 1 pole load MCB. Also in the distribution panel is the load monitoring circuit which consists of a digital voltmeter/ammeter, an alarm card to provide a System DC low alarm at 24.5VDC, and a 100A low voltage disconnect relay which is controlled by the alarm card. The LVD will disconnect the load if the system output voltage ≤ 22VDC.

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