MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used for extracting maximum available power from PV module under certain conditions. The voltage at which PV module can produce maximum power is called ‘maximum power point’ (or peak power voltage). Maximum power varies with solar radiation, ambient temperature and solar cell temperature.
Typical PV module produces power with maximum power voltage of around 17 V when measured at a cell temperature of 25°C, it can drop to around 15 V on a very hot day and it can also rise to 18 V on a very cold day.
The major principle of MPPT is to extract the maximum available power from PV module by making them operate at the most efficient voltage (maximum power point). That is to say:
MPPT checks output of PV module, compares it to battery voltage then fixes what is the best power that PV module can produce to charge the battery and converts it to the best voltage to get maximum current into battery. It can also supply power to a DC load, which is connected directly to the battery.
A MPPT solar charge controller is the charge controller embedded with MPPT algorithm to maximize the amount of current going into the battery from PV module.
MPPT is DC to DC converter which operates by taking DC input from PV module, changing it to AC and converting it back to a different DC voltage and current to exactly match the PV module to the battery.
There are many features of MPPT solar charge controller: In any applications which PV module is energy source, MPPT solar charge controller is used to correct for detecting the variations in the current-voltage characteristics of solar cell and shown by I-V curve.
MPPT solar charge controller is necessary for any solar power systems need to extract maximum power from PV module; it forces PV module to operate at voltage close to maximum power point to draw maximum available power.
MPPT solar charge controller allows users to use PV module with a higher voltage output than operating voltage of battery system.
For example, if PV module has to be placed far away from charge controller and battery, its wire size must be very large to reduce voltage drop. With a MPPT solar charge controller, users can wire PV module for 24 or 48 V (depending on charge controller and PV modules) and bring power into 12 or 24 V battery system. This means it reduces the wire size needed while retaining full output of PV module.
MPPT solar charge controller reduces complexity of system while output of system is high efficiency. Additionally, it can be applied to use with more energy sources. Since PV output power is used to control DC-DC converter directly.
MPPT solar charge controller can be applied to other renewable energy sources such as small water turbines, wind-power turbines, etc.
The benefits of MPPT solar charge controllers are greatest during cold weather, on cloudy or hazy days or when the battery is deeply discharged. Solar MPPT can also be used to drive motors directly from solar panels. The benefits seen are huge, especially if the motor load is continuously changing. This is due to the fact that the AC impedance across the motor is related to the motor's speed. The MPPT will switch the power to match the varying resistance.
Compared to the traditional solar chareg controller, maximum Power Point Tracking solar charge controllers (MPPT) are different than the traditional PWM solar charge controllers in that they are more efficient and in many cases more feature rich. MPPT solar charge controllers allow your solar panels to operate at their optimum power output voltage, improving their performance by as much as 30%.
The most traditional charge controller simply monitors the battery voltage and opens the circuit, stopping the charging, when the battery voltage rises to a certain level. Older charge controllers used a mechanical relay to open or close the circuit, stopping or starting power going to the batteries.Traditional Solar Inverters perform MPPT for an entire array as a whole. In such systems the same current, dictated by the inverter, flows though all panels in the string. But because different panels have different IV curves, i.e. different MPPs (due to manufacturing tolerance, partial shading, etc.) this architecture means some panels will be performing below their MPPT, resulting in the loss of energy.
A photovoltaic (PV) array is a constant current device. The current (amps) from a PV module remains relatively constant over a wide range of voltage. For example a typical 75-watt module delivers 4.45 amps at up to 17 volts when the sky is clear and temperature is cool. Traditional PV controllers connect the PV array directly to the battery until it reaches a full charge voltage. When this 75-watt module is connected directly to a battery in a low state of charge it will begin charging at 12 volts. The PV panel still provides about the same current, but, because PV output voltage is lower, it can only deliver 53 watts to the battery. This wastes up to 22 watts or 30% of the available power. MPPT charge controls use this extra voltage to boost charging amps to the battery.
So adding an MPPT solar charge controller to an existing system is a very popular upgrade these days as people improve and expand their systems. MPPT controllers will get the most out of your PV array, and actually are more beneficial in off-grid applications because they produce the most benefit in the cold winter months when the batteries tend to be at a lower state-of-charge—right when you need the energy the most!