Alpha Technologies Serial System Controller - Manual (Page 9)

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018-332-C0-002 Rev. B © 2001 TM
1. System Overview
1.1 Theory of Operation
The Serial System Controller (SSC) manages and provides status monitoring for powering
systems that contain single or multiple (up to six) power supplies, and a generator. It
coordinates battery charging, individual battery monitoring, and self-testing for individual
components in the system. Using a serial interface, Alpha’s Engine Control Module (ECM)
communicates with the SSC to manage generator operation.
The SSC coordinates the following control functions of the power supply system:
• Battery charging
• System self-test
• Low battery shutdown of inverters
• Initiation of low battery disconnect
• Monitoring of system configuration
• Battery temperature monitoring
• Acquisition and maintenance of data from all units in the system
• Response to queries from a digital transponder
• Monitoring of individual battery voltage
• Maintenance of critical parameters in nonvolatile memory
• Four user-defined discrete outputs, one input
SSC to serial transponder communication supports: HMS022 for individual power supplies;
HMS022 for the generator system; Alpha power system status; Alpha individual power supply
and extended status; and Alpha generator configuration and extended status.
1.1.1 Battery Charging
Each XM2 has a battery charger capable of delivering a maximum current to the
battery string. XM2s in a system configuration typically share a single string of
batteries, and each provides its maximum charging current to the string after a major
discharge event. Since this may damage the batteries, the SSC determines the
number of power supplies in the system, and limits the individual power supply
chargers so that the maximum charging current is never exceeded. The maximum
charging current for a battery string can be calculated by using the following formula:
Maximum Charging Current <= (Battery Capacity / 5)
For example, total charger current of 100 Amp Hour batteries cannot exceed 20
Amps. If a system contains five power supplies, each will be limited to 4 Amps
maximum.
The SSC waits for a unit in the system to transition into FLOAT mode, then watches
system charging current drop below a threshold, based on the number of power
supplies in the system. It then forces all of the XM2 power supplies into FLOAT mode
to complete the battery charge.
NOTE: XM2 power supplies must have firmware 3.01 or higher for SSC to
operate.