Specifications
14
3.5.2 RS485
The RS485 port on the battery charger supports the Modbus RTU protocol.
RS485 is used for point-to-point cable connection of more than one device (maximum 32 devices)
and allows for connection to PCs, PLCs and Building Management Systems (to name just a few
devices).
One advantage of the RS485 interface is the large distance specification (1.2km) when using Belden
9841 (or equivalent) cable. This allows for a large distance between the battery charger and a PC
running the DSE Configuration Suite software. The operator is then able to view the various operating
parameters.
NOTE: - For distances up to 6m (8yds) the USB connection method is more suitable and
provides for a lower cost alternative to RS485 (which is more suited to longer distance
connections).
Cable Type Two core screened twisted pair
Cable Characteristic
Impedance
120Ω
Recommended Cable Belden 9841
Belden 9271
Maximum Cable Length 1200m (¾ mile) when using Belden 9841 or direct equivalent.
600m (666 yds) when using Belden 9271 or direct equivalent.
RS485 Topology “Daisy Chain” Bus with no stubs (spurs)
RS485 Termination
120Ω. Termination resistor must be fitted externally to the ‘first’ and
‘last’ expansion module by the customer as required by the RS485
specification.
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