Installation and Operation Manual
18
SYMPTOM
PROBABLE CAUSE
ITEMS TO EXAMINE OR CORRECT
Charge current is
lower than expected,
PV current may be
low as well
Battery is highly charged
Worn out PV modules
Low insolation
PV- connected to BAT-
MPPT improperly setup
Normal operation, system will be in Acceptance or Float and
current is reduced to control battery voltage.
Replace, or use as is.
Atmospheric haze, PV’s dirty, sun low on horizon, etc.
PV- & BAT- must be separate for proper operation. PV- must
receive earth ground via shunts inside the SB3048 which
internally connect PV- to BAT-. External connection prevents
proper operation of internal shunts and measurement system.
Verify dip switch #5, verify proper MPPT setup and MPPT trim.
See Maximum Power Voltage and Optimizing MPPT sections.
MPPT Current boost
is less than expected
PV maximum power voltage
(V
MP
) is not much higher than
battery voltage, leaving little
extra power to be extracted
PV’s hot
MPPT improperly setup
May result from PV’s with low V
MP
, as PV’s with higher V
MP
produce greater power and current boost potential. PV’s with
V
MP
≥
17V work best, PV’s with <36 cells tend to work poorly.
Excessive PV wiring voltage drop due to undersize wiring, poor
connections, etc., consumes and wastes available power. This
simulates having PV’s with low V
MP
.
Battery is nearly charged and battery voltage is high. Output
during MPPT operation is “constant power” so higher battery
voltage produces less charge current.
V
MP
and available power decrease with increasing PV cell
temperature. Cooler PV’s will produce greater boost. MPPT LED
off indicates that extra power is not available from PV array. It is
normal for boost to decrease as temperature rises.
Verify dip switch #5, verify proper MPPT setup and MPPT trim.
See Maximum Power Voltage and Optimizing MPPT sections.
System appears OK,
but will not correctly
switch between
Accept. & Float
Not set for 3 stage charge
System will not switch out of Bulk
and into Acceptance or Float
System will not switch from Float
to Acceptance
System will not switch from
Acceptance to Float
Double check dip switches #10 & 11
Battery is discharged to the point where net charge current
cannot bring battery voltage up to the desired charge voltage
setpoint. PV power may be too low or loads too high.
Battery may be fully charged. System will stay in Float and not
switch to Acceptance until charge current is greater than Float
Transition Current setting. See Float Transition Current Setpoint
section. PV array may be too small for battery amp-hours. If PV
array is too small, consider using 2 stage charge.
External shunt is used and sense wires are wired reverse
polarity. Verify charge current polarity and magnitude using “I
BAT” test point. See Float Transition Current Measurement
Shunt and Setpoint sections.
Battery may not be fully charged. System will not switch to Float
until charge current drops to less than the Float Transition
Current setpoint during Acceptance. See Float Transition
Current Setpoint section.
Loads during charge may be high while using internal current
shunt. Consider using external shunt. See Float Transition
Current Measurement Shunt section.
At high ambient
temperature, charge
turns off
System temporarily shuts down
due to high heat sink
temperature
Improve ventilation or reduce PV power. Providing sufficient
ventilation or operating conditions which do not cause over
temperature shut down will improve reliability.
