Product Manual

28
SOLAR BATTERY CHARGING
29
MORNINGSTAR CORPORATION
4.04.0
Battery Voltage Sense: Connecting a pair of voltage sense wires from the
controller to the battery is recommended. This allows a precise battery
voltage input to the controller and more accurate battery charging.
See
Section 4.3 for more information.
Temperature Compensation: All charging setpoints are based on 25˚C (77˚F).
If the battery temperature varies by 5˚C, the charging will change by 0.15
volts for a 12 volt battery. This is a substantial change in the charging of the
battery, and a remote temperature sensor is recommended to adjust charging
to the actual battery temperature.
See Section 4.3 for more information.
Day-Night Detection: The TriStar will automatically detect day and night
conditions. Any functions that require measuring time or starting at dawn,
for example, will be automatic.
PWM Noise: In some installations, the PWM charging may cause audible
noise in certain equipment. If this occurs, the PWM can be changed to “On-
Off” solar charging to reduce the noise. This requires DIP switch number 8
to be turned On. However, it is strongly recommended to try to remedy the
noise problem with grounding or filtering first, because the benefits from
PWM battery charging are significant.
Battery Types: The TriStar’s standard battery charging programs are suitable
for a wide range of lead-acid battery types. These standard programs are
reviewed in the following Section 4.2. A general review of battery types and
their charging needs is provided in Section 9.0.
4.2 Standard Battery Charging Programs
The TriStar provides 7 standard battery charging algorithms (programs) that
are selected with the DIP switches
(see Step 3 in Installation) . These standard
algorithms are suitable for lead-acid batteries ranging from sealed (gel, AGM,
maintenance free) to flooded to L-16 cells. In addition, an 8th DIP switch
provides for custom setpoints using the PC software.
The table below summarizes the major parameters of the standard charging
algorithms. Note that all the voltages are for 12V systems (24V = 2X, 48V = 4X).
All values are 25ºC (77ºF).
A. B. C. D. E. F. G.
DIP PWM Time Equalize Max Equal.
Switches Battery Absorp. Float Equal. in Equal. Interval Cycle
(4-5-6) Type Voltage Voltage Voltage (hours) (days) (hours)
off-off-off 1 - Sealed 14.0 13.4 none – – –
off-off-on 2 - Sealed 14.15 13.4 14.2 1 28 1
off-on-off 3 - Sealed 14.35 13.4 14.4 2 28 2
off-on-on 4 - Flooded 14.4 13.4 15.1 3 28 4
on-off-off 5 - Flooded 14.6 13.4 15.3 3 28 5
on-off-on 6 - Flooded 14.8 13.4 15.3 3 28 5
on-on-off 7 - L-16 15.0 13.4 15.3 3 14 5
on-on-on 8 - Custom Custom Custom
Table 4.2 Standard Battery Charging Programs
A. Battery Type - These are generic lead-acid battery types. See Section 9.0
for more information about battery types and appropriate solar charging.
B. PWM Voltage–This is the PWM Absorption stage with constant voltage
charging. The “PWM voltage” is the maximum battery voltage that will be
held constant. As the battery becomes more charged, the charging
current tapers down until the battery is fully charged.
C. Float Voltage–When the battery is fully charged, the charging voltage will
be reduced to 13.4 volts for all battery types. The float voltage and
transition values are adjustable with the PC software.
See Section 4.5 for
more details.
D. Equalization Voltage–During an equalization cycle, the charging voltage
will be held constant at this voltage.
E. Time in Equalization–The charging at the selected equalization voltage
will continue for this number of hours. This may take more than one day
to complete.
See Section 4.4.
F. Equalization Interval–Equalizations are typically done once a month. Most
of the cycles are 28 days so the equalization will begin on the same day of
the week. Each new cycle will be reset as the equalization starts so that a
28 day period will be maintained.
G. Maximum Equalization Cycle–If the solar array output cannot reach the
equalization voltage, the equalization will terminate after this many hours
to avoid over gassing or heating the battery. If the battery requires more
time in equalization, the manual pushbutton can be used to continue for
one or more additional equalization cycles.
These 7 standard battery charging algorithms will perform well for the
majority of solar systems. However, for systems with specific needs beyond
these standard values, any or all of these values can be adjusted using the
PC software.
See Section 7.0 .
4.3 Temperature Effects & Battery Voltage Sense
4.3.1 Remote Temperature Sensor (RTS)
The RTS is used for temperature compensated battery charging. As the battery gets
warmer, the gassing increases. As the battery gets colder, it becomes more resistant
to charging. Depending on how much the battery temperature varies, it may be
important to adjust the charging for temperature changes.
There are three battery charging parameters that are affected by
temperature:
PWM Absorption
This is the most important part of charging that is affected by temperature
because the charging may go into PWM absorption almost every day. If the
battery temperature is colder, the charging will begin to regulate too soon
and the battery may not be recharged with a limited solar resource. If the
battery temperature rises, the battery may heat and gas too much.
Equalization
A colder battery will lose part of the benefit of the equalization. A warmer
battery may heat and gas too much.