Outback Power Systems GS8048 - Manual (Page 16)

Planning
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 Backup: This mode is intended for systems that have the utility grid available. This source will flow through
the Radian inverter to power the loads unless utility power is lost. If utility grid power is lost, then the Radian
inverter will supply energy to the loads from the battery bank until the power is back online.
 Minigrid: This mode is intended for systems that have the utility grid as an input and a sizable amount of
renewable energy production. The system will run off the renewable energy production until the battery
voltage falls to a specified low level. When this occurs, the Radian inverter will connect to the utility grid,
which will power the loads. The Radian inverter will disconnect from the utility grid when the batteries are
sufficiently recharged.
Renewable Energy
The Radian Series Inverter/Charger cannot connect directly to photovoltaic arrays, wind turbines, or
other renewable sources. The batteries are the inverter’s primary source of power. However, if these
sources are used to charge the batteries, the inverter can use their energy by drawing it from the
batteries.
The renewable source is always treated as a battery charger, even if all of its power is used
immediately. The renewable source must have a charge controller or some way to prevent
overcharging. OutBack Power’s FLEXmax charge controllers can be used for this purpose, as can
other products. The GSLC will facilitate the mechanical and electrical connections for up to two
FLEXmax charge controllers.
Battery Bank
When planning a battery bank, consider the following:
 Cables: Recommendations for battery cable size and length are shown on page 25. The maximum length
will determine the placement of the battery bank. Other local codes or regulations may apply and may take
priority over OutBack recommendations.
 Battery Type: The Radian inverter/charger works best with lead-chemistry batteries intended for deep
discharge. These include batteries for marine, golf-cart, and forklift applications. They also include gel-cell
batteries and absorbed glass-mat (AGM) batteries. OutBack Power recommends the use of batteries
designed specifically for renewable energy applications. Automotive batteries are strongly discouraged and
will have a short life if used in inverter applications. Nickel-based batteries are discouraged due to
limitations in the Radian charger. Lithium-based batteries and other advanced battery technologies may
require special considerations. Please contact OutBack Technical Support at +1.360.618.4363 before
implementing advanced battery technologies.
 The Radian inverter/charger is designed to work with a 48-volt battery bank. Before constructing a battery
bank, confirm the nominal voltage of individual batteries.
 Bank Size: In backup or off- grid applications, the battery bank size should be calculated based on
expected loads and run time.
~ To prevent the inverter’s charger from overcharging, the minimum recommended battery bank size is
350 amp-hours for every Radian inverter/charger installed on the system.
~ If other charging devices are present, the minimum bank size should be determined by adding the
inverter(s) charge rate to any other chargers and multiplying the result by five. Example: If the system’s
combined charge rate was 160 Adc, the minimum battery bank size should be 800 amp-hours.
 Systems intended to bridge short-term outages can use smaller battery banks. In these cases, the bank can
be as low as 200 amp-hours per inverter. However, the charge rate must be decreased to half the inverter’s
maximum using the MATE3. (See the MATE3 manual.) One of the following conditions must also be true.
~ The system is equipped with a backup generator that is programmed for automatic start, or
~ Typical grid loss is 30 minutes or less, or
~ The loads are less than 2 kW.