Installation Guide
MORNINGSTAR CORPORATION
39
4.0 OPERATION
38
4.0
BATTERY SOC LEDS
Three (3) battery state-of-charge LEDs indicate the level
of charge on the battery. The SOC indication is based on
battery voltage set-points alone, which only provides an
approximation of the actual state of charge of the battery.
Table 3 lists the SOC LED indications.
SOC LED Indication Battery Status Load Status
Green
Fast Flashing
(2 Flash / sec)
Equalize Charge Load On
Green
Med. Flashing
(1 Flash / sec)
Absorption Charge Load On
Green
Slow Flashing
(1 Flash / 2 sec)
Float Charge Load On
Green On solid Nearly Full Load On
Yellow On solid Half Full Load On
Red
Flashing
(1 Flash / sec)
Battery Low
LVD Warning
(Load On)
Red On solid Battery Empty
LVD
(Load Off)
Table 3. Battery SOC LED denitions
NOTE:
An error condition exists if multiple Battery SOC LEDs
are ashing. See Section 5.1 Error Indications for more
information.
4.2 TrakStar
TM
MPPT Technology
The SS-MPPT utilizes Morningstar’s TrakStar Maximum
Power Point Tracking technology to extract maximum power
from the solar module(s). The tracking algorithm is fully
automatic and does not require user adjustment. Trakstar
technology will track the array maximum power point voltage
(V
mp
) as it varies with weather conditions, ensuring that
maximum power is harvested from the array through the
course of the day.
Current Boost
In many cases, TrakStar MPPT technology will “boost” the
solar charge current. For example, a system may have 2
Amps of solar current owing into the SS-MPPT and 5 Amps
of charge current owing out to the battery. The SS-MPPT
does not create current! Rest assured that the power into
the SS-MPPT is the same as the power out of the SS-MPPT.
Since power is the product of Voltage and current (Volts x
Amps), the following is true*:
(1) Power Into the SS-MPPT = Power Out of the SS-MPPT
(2) Volts In x Amps In = Volts Out x Amps Out
* assuming 100% efficiency. losses in wiring and conversion exist.
If the solar module’s V
mp
is greater than the battery
voltage, it follows that the battery current must be
proportionally greater than the solar input current so that
input and output power are balanced. The greater the
difference between the maximum power Voltage and battery
Voltage, the greater the current boost. Current boost can be
substantial in systems where the solar array is of a higher
nominal voltage than the battery as described in the next
section.