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Midnite Solar
Outback Controller
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Why MPPT?

Solar Voltaic Charge Controllers

Solar voltaic panel output should never be directly connected to a battery as the unregulated current from the solar panels will damage the batteries.  The primary function of a Solar Charge controller is to fully and properly charge a battery bank without permitting reverse current flow to the solar voltaic panels at night.

Primary of types charge controller:

 On/Off  type Solar Charge Controller

  • Disconnects module when high battery voltage is reached (≈ 14V)

  • Reconnects module when battery voltage lowers (≈ 13V)

  • Control may be relay type or solid state

  • You will find these in retail outlets and big box stores

 Pulse Width Modulation (PWM) Solar Charge Controller

  • When desired battery voltage is reached (≈ 14V) output turns on/off quite rapidly (100Hz - 50KHz)

  • Battery voltage held constant, producing a more fully charged battery

  • The most popular charge controller series of this time is the C-? series from Xantrex

 Maximum Power Point Tracking (MPPT)

  • Provides PWM type battery voltage control

  • Extracts all available power from the PV module

  • MPPT technology can increase charge current up to 30% or more compared to traditional charge controllers

  • Manufacturers of MPPT controllers include Outback, Morningstar, Blue Sky and Xantrex

Sizing the Solar Charge Controller

Most Solar Charge Controllers are rated by the amount of array amperage (current) and voltage they can handle. Amperage ratings run from 1 amp to 60 amps, voltages from 6 to 60 volts. Cold weather, reflection and edge-of-cloud light refraction can increase PV panel output.  The charge controller should be sized to handle 25% more current than the panels are rated for.  Most people add solar panels as they go along , size the charge controller to handle your needs into the future.