MPPT Charge Controllers

  • Maximum Power Point Tracking (MPPT) will enable you to have a
    solar panel array with higher voltage than the battery bank. The
    controller will automatically convert the voltage to your system
    requirement.
  • MPPT Charge Controllers enable you to use smaller gauge wiring
    which can add up to significant savings in a large scale project.  
    When the voltage is doubled (12 to 24 volts), the current decreases
    by half, which allows for the smaller gauge wiring.

  • For a 1000 watt solar panel array that operates at 48 volts DC, with
    a 24VDC battery bank. The formula to calculate the output current is
    Power = Volts x Amps
    The power is 1000 watts, the battery bank at 24 volts,
    therefore:
    1000 watts = 24 volts x Amps
    Amps = 1000 watts/ 24 volts
    Amps = 41.7A

  • It is still recommended to increase this value by 25% to account for
    extraordinary conditions.  The additional 25% puts us over 50A.  
  • MPPT charge controllers can handle a higher input voltage from the
    solar panel array than the battery bank's voltage, you can also use
    these charge controllers with solar panels that have odd voltages
    that don't match any typical system voltage (i.e. 12, 24 or 48V). For
    instance, you could have a solar panel that has a nominal voltage of
    57 volts and charge and battery bank that's 24 volts efficiently with
    an MPPT charge controller.
  • MPPT charge controllers have an upper voltage limit that they can
    handle from the solar panel array. It's important that you make sure
    than there is no condition that the solar panel array voltage will go
    above this limit or you will like burn out the controller. You want to
    make sure that the open circuit voltage of the solar panel array
    does not go above this limit. You also want to give yourself a little
    bit of a margin for an error to take in account the possibility that a
    solar panel array's voltage will actually increase the colder it gets.  
    It is recommended that you allow a 10% margin of error.
Solar Charge Controllers
A solar charge controller is needed in virtually all solar power systems
that
utilize batteries.  The job of the solar charge controller is to regulate
the power going from the solar panels to the batteries to prevent
overcharging.  Overcharging batteries will significantly reduce battery
life and possibly damage the batteries to the point that they are
unusable.

Basic Charge Controllers
The most basic charge controller simply monitors the battery voltage
and opens the circuit, stopping the charging, when the battery voltage
rises to a certain level.  

Pulse Width Modulation (PWM)
Modern charge controllers use pulse width modulation (PWM) to slowly
lower the amount of power applied to the batteries as the batteries get
closer to fully charged.  This type of controller allows the batteries to be
more fully charged with less stress on the battery, extending battery
life.  It can also keep batteries in a fully charged state (called “float”)
indefinitely.  PWM is more complex, but doesn’t have any mechanical
connections to break.

Maximum Power Point Tracking (MPPT)
The most recent and best type of solar charge controller is called
maximum power point tracking or
MPPT.  MPPT controllers convert
excess voltage into amperage.  This has advantages in a couple of
different areas.

  • Most solar power systems use 12 volt batteries.  Solar panels can
    deliver far more voltage than needed to charge a 12V battery.  By
    converting the excess voltage into amps, the charge voltage can be
    kept at an optimal level while the time required to fully charge the
    batteries is reduced.  This allows the solar power system to
    operate optimally at all times.

  • Another area that is enhanced by an MPPT charge controller is
    power loss.  Lower voltage in the wires running from the solar
    panels to the charge controller results in higher energy loss in the
    wires than higher voltage.  With a PWM charge controller used with
    12v batteries, the voltage from the solar panel to the charge
    controller typically has to be 18v.  Using an MPPT controller allows
    much higher voltages in the wires from the panels to the solar
    charge controller.  The MPPT controller then converts the excess
    voltage into additional amps.  By running higher voltage in the wires
    from the solar panels to the charge controller, power loss in the
    wires is reduced significantly.

  • MPPT charge controllers are more expensive that PWM charge
    controllers, but the advantages are worth the cost.

Reverse Current

The final function of modern solar charge controllers is preventing
reverse-current flow.  At night, when solar panels aren’t generating
electricity, electricity can actually flow backwards from the batteries
through the solar panels, draining the batteries.  The charge controller
can detect when no energy is coming from the solar panels
and open the circuit, disconnecting the solar panels from the batteries
and stopping reverse current flow.
Sunforce  Solar Charge Controller
TD-60012   7 Amp / 12V / 150W
www.millenniumplanet.com
The Charge controller is integral to the life and efficiency of the solar power system.

  • Optimizes the power from the solar panels,
  • Protects your battery supply and extends life
  • Choose an option that is scalable and that fits your power load and have sufficient battery storage space.
  • Charge controllers are rated and sized by the solar panel array current and system
  • voltage. Most common are 12, 24, and 48-volt controllers.
  • Amperage ratings normally run from 1 amp to 60 amps, voltages from 6-60 volts. If each module produces 7.5 amps
    and two modules are used, the system will produce 15 amps of current at 12 volts.
  • Generally, the amperage should be increased by 25% to offset clouds, weather, seasonal and other natural
    variations.
  • Adding 25% to the 15 amps would bring it to 18.75.  Look for the next closest unit available, in this example a 20-amp
    controller is an excellent fit.  The larger the better, if you are planning to expand the system later and are willing to
    invest more, but 20-amp would be ideal.
Xantrex XW Solar MX60
50-Amp Charge Controller