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The SD300 has been designed to provide a rapid means of disconnecting batteries or other power supplies in the event of serious electrical faults.  The SD300 combines the dual function of a manual disconnect and coil operated line contactor.  The benefits of this design include compact size and reduced installation costs combined with an electrical capacity sufficient for most small and medium size electric vehicles.

Whilst the switches are primarily intended for use with battery powered vehicles, they are also suitable for use with static power systems. All types are capable of safely rupturing full load battery currents in the event of an emergency.  Optionally, a fuseholder for an inline fuse can be provided pre-fitted.  This modification adjusts the positions of the coil terminals and is suitable for ANL or MEGA fuse configurations.

The Use of Battery Disconnecting Switches in Electric Vehicles

Modern battery powered electric vehicles are inherently very reliable and safe. However, even when sophisticated electronic controllers are used it is desirable to have a means of disconnecting the battery in the event of an emergency, such as a vehicle failing to stop or an electrical short circuit.  In many countries it is mandatory to fit one or more devices to achieve an emergency disconnection of the battery.


When fitted with magnetic blowouts the polarity marked on the contact housing must be observed when connecting the main terminals.  Ensure that the switches are installed in a position where heavy arcs emanating from the switch cannot damage or electrically jump across to adjacent parts.  The switch is to be used to rupture current in an emergency or as a no-load isolator.

Do not use as a regular On-Load Switching Device.

SD300 Technical Information

InterruptedRating ( Ith )Uninterrupted
Thermal Current Rating - 300A
Intermittent Current Rating:
30% Duty - 550A
40% Duty - 475A
50% Duty - 425A
60% Duty - 385A
70% Duty - 360A
Rated Fault Current Breaking Capacity (Icn) 5ms Time Constant: (In accordance with UL583*)
Blowouts 1000A at 80V D.C.
No Blowouts 1000A at 48V D.C.
Rated Fault Current Breaking Capacity (Icn) Resistive Load: (In accordance with UL508*)
Blowouts -
No Blowouts -
Maximum Recommended Contact Voltages
Blowouts 96V -
No Blowouts 48V -
Typical Voltage Drop per pole across New Contacts at 300A 30mV

Mechanical Durability > 3,000,000 Cycles
Coil Voltage Available (Us) (Rectifier board required for A.C.) 6 - 240V

SD300 Features

Component Configurations
Coil Suppression
Coil Terminations

%s Resources

SD300 Data Sheet

  • Format: .pdf
  • Size: 1,101kb

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  • The SD300 has the following optional components available: