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Operation
20 900-0020-01-00 Rev A
Battery Charging
IMPORTANT:
Battery charger settings need to be correct for a given battery type. Always follow
battery manufacturer recommendations. Making incorrect settings, or leaving them at
factory default settings, may cause the batteries to be undercharged or overcharged.
The inverter uses a “three-stage” battery charging process. The three stages are Bulk, Absorption, and
Float. These stages follow a series of steps, which are shown on graphs (see page 21).
NOTES
:
The process shown in Figure 3 also includes the step of selling power back to the utility, as this is integrally
tied with the battery charger. This step, and Figure 3, are only applicable when the Radian inverter is in the
Grid Tied
input mode.
The process shown in Figure 4 eliminates Silent, Float Timer, and other parts of the process. Figure 4 is only
applicable when the Radian inverter is in the
Generator
input mode.
The target points and time limits cited under various steps are also used by the inverter’s Offset function.
(See page 19.) These items are settable using the MATE3 system display. (See the MATE3 Owner’s Manual.)
Charging Steps
No Charging
If the inverter is not charging, any of the following conditions may apply:
The unit is inverting or not connected to a qualified AC source.
The unit is connected to an AC source but is in a mode or stage that does not use the charger. (Silent mode is
one example.)
The unit is connected to an AC source but the charger has been turned off.
Bulk Stage
This stage activates the charger. This is the first stage in the three-stage charge cycle. It is a
constant-current stage which drives the battery voltage up. This stage typically leaves the batteries at
75% – 90% of their capacity, depending on conditions.
Target point:
Absorb Voltage
setting. The default setting is 57.6 Vdc.
The initial DC current is the maximum current the charger can deliver. It will begin at the charger’s
specified maximum, but will gradually decrease as the voltage increases. This is a tradeoff in wattage
and is normal for the charger.
Absorption Stage
This is the second stage of charging. It is a constant-voltage stage. Current varies as needed to
maintain the voltage, but will typically decrease to a very low number over time. This “tops off the
tank”, leaving the batteries at essentially 100% of capacity.
Target point:
Absorb Voltage
setting.
Time limit:
Absorb Time
setting. This timer counts down from the inception of the Absorption stage
until it reaches zero. The timer can be viewed. (See the MATE3 manual.)
For multiple inverters only:
The charging of multiple stacked inverters is synchronized and is governed by the master. When the
master inverter reaches the end of Absorption (and other stages), the slaves will exit Absorption as