Alpha Technologies XM3-HP Series - Technical Manual - Manual (Page 28)

28 017-882-B0-001 Rev. C2 (10/2013)
1.0
Introduction
1.3 Alpha XM3-HP CableUPS Layout, continued
1.3.4 Smart AlphaGuard
1.0 Introduction, continued
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.
1.3.4.1 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.
There are two SAG models available, one model for 1–2 strings, and one model for 1–4
strings.