A solar charge controller regulates the voltage and current coming from the solar panels going to the battery to keep them from overcharging. For instance, most 12 volt panels deliver about 16 to 20 volts as batteries need around 14 to 14.5 volts to get fully charged. So the charging current going into the battery, if unregulated, may damage it. There is an array of charge controllers available in all shapes, sizes, features, and price ranges. Maximum power point tracking (MPPT) controllers are the best in controllers to get full power out of solar panels. They follow an MPPT algorithm to calculate the maximum power out of the solar panel at any instant of time and accordingly, harvest the power coming from the panels. Although highly priced, they are ultimate and come with high efficiencies in the 94 per cent to 98 per cent range. They make good savings in larger systems as they provide 10 per cent to 30 per cent more power to the battery. They range from a small 4.5amp controller to a 60 to 80amp programmable controller with all communication peripherals and configuration capabilities. Two or more 40 to 80amp units can be wired in parallel for higher currents. New controllers come with simple LED indicators or digital meters to show battery voltages and current coming from a panel. Mentioned below are reference designs of some very good solar charge controllers employing MPPT technique. Let’s take a look.
- Solar Power MPPT Controller for 12V/24V systems: The design explains a Maximum power point tracking (MPPT) solar controller that can charge 4 batteries in series or parallel. The design is flexible for use with 10W to 30W Solar Panels and can be used in parallel with other systems. The solar controller efficiency operates at 88 per cent for the 12V system and 91 per cent for the 24V system. The design takes an example of an off grid solar streetlamp system consisting of high power LEDS, a lead acid battery, a solar controller, and a solar panel. For a 30W solar controller connected to a 30W solar panel and loaded with a battery type constant voltage load, the error in finding the maximum power point is less than 5 per cent. More on this Reference Design
- Flexible MPPT Solar Charge Controller for upto 48V systems: This reference design explains a 20A Maximum Power Point Tracking (MPPT) solar charge controller targeted for small and medium power solar charger solutions. The design is flexible and supports inputs from both 12V and 24V solar panels and can charge 12V/24V batteries with up to 20A output current. The design can easily be configured for a system voltage of 48V and a system current of 40A. This is possible by changing the MOSFETs to 100V rated parts and using the TO-220 package version of same MOSFETs. The design includes configurable features like reverse battery protection, software programmable alarms and hardware indications. The design has an operating efficiency of above 96 per cent at full load in both 24V and 12V systems. The form factor of the board is kept small. More on this Reference Design
- MPPT Solar charge controller based on PowerPSoC Power Controller: This reference design describes a MPPT Solar Charger to control and improve the charge delivered to lead acid batteries with the help of Maximum Power Point Tracking (MPPT) algorithm. The MPPT algorithm is intended to maximise the solar energy harvested from the panel by determining the peak power output of the solar panel. The design is built around a PowerPSoC power controller device that provides design flexibility by providing reconfigurable power levels without hardware modifications and additional hardware integration. The PowerPSoC also ensures safety by indicating battery over voltage, no battery connected, battery under voltage, and low panel voltage. The design works with multiple types of lead-acid batteries, including flooded, absorbed glass mat, sealed, and gel batteries. More on this Reference Design
- Solar Charge Controller with High MPPT Efficiency: Here is a reference design of a compact photovoltaic charge controller that implements a Maximum Power point tracking algorithm to charge the battery by taking power from the solar panels. The design uses a small, low-power MPPT IC called the MPT612, which gives an MPPT efficiency of 98 per cent. It also enables the battery to supply power to the DC loads connected to the controller. The design is compact and features NXP’s ARM Cortex-M3 LPC1788 microcontroller to control its functions. A number of protection mechanisms and system status indications are provided on the board. Multiple serial interfaces (I2C, UART, SPI, SSP) are provided for debugging, configuration of PV panel parameters, and data logging. More on this Reference Design