Now that solar power is cheaper than coal-based electricity in India, public interest is gravitating towards off-grid solar power as an alternative. One prime market segment that has directly benefited from the transition to solar electrification is solar charge controllers. This article briefly introduces some newly launched products in the category.
By Shruti Mishra
In any alternative energy power system that has a battery bank, charge controllers are used to ensure that the right amount of power flows to the batteries. In the case of solar power systems, solar charge controllers perform the vital function of protecting the batteries and automating the charging process.
In an off-grid system, the solar charge controller is placed between the solar panel and the deep cycle battery, from where it regulates the power going from the panel to the batteries while ensuring that batteries do not get damaged by overcharging. Apart from this, these electronic modules also keep a check on the reverse flow of current from the battery to the solar array at night, thereby preventing batteries from draining out of charge. Some of the latest charge controllers are also equipped with capabilities like lighting or load control, which help in achieving maximum PV power and in managing power.
Types of technology involved
Simple one-or two-stage controllers are considered as the first version of a solar charge controller. These systems rely on relays or shunt transistors in order to maintain voltage in one or two steps. Highlighting their downside, Kartik S. Aiyar, CEO, Vensai Solutions, says, “Regular relay based controllers, on reaching the cut-off level, disconnect the PV. Solar charge controllers shouldn’t be like that. First, a solar charge controller should have zero voltage drop, so that maximum power can be obtained from the PV arrays, and it should be free from mechanical devices like a relay, etc. In off-systems, a solar charge controller is mainly used for battery charging. So a charge controller should have the following functions—float charging, boost charging and equalisation mode. Just switching power on or off is not sufficient.”
However, a significant difference can be seen between the older solar chargers and those that we see today. These days, solar charge controllers are mainly available with two different technologies, pulse width modulation (PWM) and maximum power point tracking (MPPT). Let’s take a look at how both of these perform in a system and what their different functionalities are.
PWM solar charge controllers: This is a relatively older and cheaper technology, using which the PWM solar charge controllers match the voltages of the panels to that of the battery, thereby tapering the panel output voltage. In this technology the amount of current and voltage lost in the pulling down process is reduced to next to nothing.
MPPT solar charge controllers: MPPT is the latest technology being used in solar charge controllers, and is more efficient than PWM technology. Unlike the non-MPPT solar chargers, this technology establishes an indirect connection between the PV array and battery bank. MPPT uses a DC-to-DC voltage converter that converts excess PV voltage into extra current at a lower voltage without losing power. In comparison to a PWM controller, the output power of an MPPT charge controller is always 10 per cent to 30 per cent more. This happens because MPPT charge controllers force PV modules to draw the maximum available power by enabling them to operate a voltage close to the maximum power point.
“MPPT solar charge controllers are used to extract the maximum available power from the PV module. The voltage at which the PV module can produce maximum power is called ‘maximum power point’ (or peak power voltage). Maximum power varies based on solar radiation, ambient temperature and the solar cell’s temperature. In regular charge controllers (PWM), whatever the panel voltage may be, it’s pulled down to the battery voltage. The efficiency would be only 60 per cent to 80 per cent when compared to the MPPT solar charge controller,” says Suresh Kumar, managing director, Vispra Power Controls.
Factors to consider before investing in a solar charge controller
Temperature conditions: Since these charge controllers are capable of using a solar array’s excess voltage, MPPT charge controllers are preferred mostly for colder ambient temperatures. On the other hand, PWM charge controllers are good for warmer ambient temperatures as they are not capable of charging batteries with any excess input voltage.
System size: MPPT charge controllers can efficiently manage a string of solar arrays and are best suited for systems rated above 150kW. PWM controllers, on the other hand, are best for smaller systems like residential rooftop and small commercial applications.
Array to load ratio: For a system where the array size is relatively large compared to the load being catered to, PWM charge controllers are a better choice. This is because they can efficiently regulate the charging at a much cheaper rate than their MPPT counterparts.
Why solar charge controllers are gaining popularity
The government of India is making aggressive moves to increase the country’s solar energy supply. The declining cost of solar panels and the recent historic drop in the solar power tariff at the Bhadla solar power auction indicate that consumers are ready to embrace this renewable power source. Also, the tropical location of the country and the ease of installing solar panels are major factors that have resulted in wide scale adoption of solar based electrification in the country.
With the rise in demand for solar electricity, solar charge controllers have also gained traction—in order to extract maximum power from the solar arrays.
Benefits of using solar charger
- Prevents overcharging or over discharging of batteries
- Reduces system maintenance and improve battery life
- Blocks reverse flow of current
- Provides protection from electrical overload
Application areas
- Solar home systems
- Recreational vehicles
- Solar street lighting systems
- Solar water pump systems
- Hybrid systems
- Standalone systems
- Solar boats
- Solar power gas detection systems
Tip for designers of solar charge controllers
“The first and most important task for designers of solar charge controllers is to find out how the design is going to increase the life of the battery and safeguard it. I believe that a solar charge controller should be designed in such a way that it must save the battery, increase the battery life and should give maximum possible efficiency,”- Suresh Kumar, managing director, Vispra Power Controls.
Latest products available in the market
Model: V-SOL MPPT, Manufacturer: Vensai Solutions
The V-SOL MPPT solar charge controllers are engineered to be durable and efficient. They continuously maintain the correct charge level on the battery and ensure a seamless power transition to battery power when needed. These charge controllers allow maximum solar array current to flow into the battery. They have a front panel LED display that indicates the mode of operation and the charge status of the battery.
Key features
- Operating PV range: 11V to 72V
- Operating temperature range: -20°C to +50°C
- Operating current range: 10A to 120A
- Modes of operation: Boost mode, normal mode, buck mode and charge completion mode
- Compact size and easy to install
Contact: www.vensaisolutions.in
Model: CC-MPPT-HV-50A, Manufacturer: Systellar Innovations
This high voltage MPPT based solar charge controller uses the latest IGBT technology to offer a high solar panel input voltage of up to 750V DC. The CC-MPPT-HV-50A measures the current being supplied or consumed by the DC load and, if necessary, limits the battery charging current to prevent damage to the battery. It provides a ‘20-character x 8 rows’ LCD display, which shows all the parameters of interest in one screen itself. It also provides for the storage of important operation data for the last 365 days, which can be transferred to a PC over the RS485/RS232C interface.
Key features
- Maximum charging current: 50A
- Maximum solar panel voltage: 750V
- Microcontroller: ARM based 32-bit advanced microcontroller
- Dimensions (L x W x H): 550 mm x 440mm x 330mm
- Weight: 35kg
- Protection: Fuse protection on battery connection, reverse PV connection, and reverse battery
- connection (with beeper warning)
Contact: www.systellar.co.in
Model: MPPT charge controller, Manufacturer: Vispra Solar
The Vispra solar charge controller is a DSP based system with a three-stage charging process. The company’s fast sweep tracking technology helps to harvest the most energy available from the PV array, even in partial shade conditions. This IGBT-based charge controller also has a user friendly indication system to let users know the battery’s charge status.
Key features
- Operating voltage range: 48V to 360V
- Operating current range: 10A to 60A
- Built-in temperature compensation
- RS232 enabled data logging
- Remote monitoring via Zigbee/GPRS
Contact: www.vispra.com
Model: V-SOL 5C12, Manufacturer: Vensai Solutions
The V-SOL 5C12 model is designed to provide reliable charging and power management of solar power supplies for industrial equipment. These controllers are engineered to be durable and efficient. The charging mode uses PWM (pulse-width modulation) for high efficiency. Front panel LED indicators show the status of the battery charge.
Key features
- Nominal voltage: 12V DC
- Maximum PV voltage: 22V DC
- Ambient temperature range: -20°C to +50°C
- Dimensions (L x W x H): 165mm x 125mm x 60mm
- Case protection: IP20
- Weight: 0.5kg
Contact: www.vensaisolutions.in
