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017-882-B0-001 Rev. E (06/2018)
1.0 Introduction, Continued
1.3.4 Smart AlphaGuard
The Smart AlphaGuard (SAG) is an optional device that maximizes battery life.
The SAG enables the XM3-HP system to gather individual battery voltages and balance the batteries. A description of the
SAG's operation and features follows.
Theory of Operation
The Smart AlphaGuard (SAG) communicates directly with the XM3. The SAG sends battery data, unit states and alarms
to the XM3 and the XM3 sends control messages back to the SAG.
The SAG is a battery balancer with multiple string capability and integrated intelligent functions. It minimizes differences
in individual battery voltages during the charging of the batteries (all modes except REST) by transferring charge from
a battery with a higher voltage to the batteries with lower voltages within a string. The SAG's balancer circuit switches
between strings enabling a single SAG to service up to four strings of batteries.
To accomplish this the SAG periodically measures all the battery voltages. These measurements are sent to the system
master XM3. Voltage measurements are used to determine the level of balance of the batteries and determine if there is
one or more batteries that need to be balanced. The level of balance will determine which string the SAG will focus on.
The SAG selects the string with the highest delta mean (Vbat-Vmean) to balance first.
Units configured with XM3 firmware V1.13.0 and higher, will have the Smart AlphaGuard (SAG) battery balancer disabled
at initial power up. Once the battery charger reaches FLOAT charging mode (the charging time may vary due to battery
state and condition), the power supply will perform a mandatory automatic two-minute self-test to verify the health of the
battery strings. Upon successful completion of the test, the SAG battery balancer will be enabled. If the self-test fails, refer
to the Smart Display to view any active alarms.
If the unit displays a "Self-Test Fail" alarm, the alarm is latched and cycling the XM3-HP Inverter Module will not clear the
alarm. It will be necessary to clear the fault condition and re-run the Self-Test.
The SAG option does not support the AlphaCell XTV 18v4 battery, battery balancing will be disabled.
