PWM vs. TrakStar MPPT Technology

Traditional PWM vs Morningstar’s TrakStar™ MPPT Technology
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PWM. It would not be economical to use MPPT in such a situation. Average temperature at the site
should be a factor considered when making a regulator choice (See Appendix).
3. Systems in which array power output is significantly larger than the power draw of the system loads
would indicate that the batteries will spend most of their time at full or near full charge. Such a
system may not benefit from the increased harvesting capability of an MPPT regulator. When the
system batteries are full, excess solar energy goes unused. The harvesting advantage of MPPT may
be unnecessary in this situation especially if autonomy is not a factor.
Technology Comparison
PWM Charge Control
MPPT Charge Control
PV array & battery voltages must match
PV array voltage can be much higher
than battery voltage
Operates at battery voltage so it
performs well in warm temperatures and
when the battery is almost full
Operates above battery voltage so it is
can provide “boost” in cold
temperatures and when the battery is
low.
Typically recommended for use in
smaller systems where “boost” benefits
are minimal.
170W or higher to take advantage of
“boost” benefits more
Must use off-grid PV modules typically
with Vmp ≈ 17 to 18 Volts for every 12V
nominal battery voltage
Enables the use of lower cost/grid-tie
PV Modules helping bring down the
overall PV system cost
PV array sized in Amps (based on current
produced when PV array is operating at
battery voltage)
PV array sized in Watts (based on the
Controller Max. Charging Current x
Battery Voltage)
Simpler series switching charge control
circuit
Additional Energy Harvest by operating
at PV peak power point rather than
battery voltage