B-3
Appendix B - Battery Information
©2002 Xantrex Technology Inc. All Rights Reserved.
P/N 975-0049-01-01 Rev A 10/2002
Battery-Bank Sizing
The battery-bank’s size determines the length of time
the unit can continue to supply AC output power. The
larger the bank, the longer the unit can run. An
undersized battery bank results in reduced battery life
and shorter unit run times.
In general, the battery-bank should be designed so the
batteries do not discharge more than 50% of their
capacity on a regular basis. Discharging up to 80% is
acceptable on a limited basis, such as a prolonged utility
outage. Totally discharging a battery results in
permanent damage and reduced battery life.
For off-grid, stand-alone applications, design a battery-
bank that can power the loads for 3–5 days without
requiring recharging. To duplicate the conditions on
sunless days or windless periods, the power supplied
from other sources (i.e., solar, wind, hydro, etc.) is not
included in this calculation. This is often referred to as
the “number of days of autonomy.” If the system is a
hybrid, with daily generator run periods, the battery-
bank size can be smaller.