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.
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.
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.