Solar charge controllers: Playing a key role in solar power distribution systems

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With several initiatives undertaken by Central and state governments to encourage the use of renewable resources, the solar energy sector has gained significant momentum and attention. This has dramatically increased the demand for solar charge controllers.

By Potshangbam July

The solar charge controller market is growing rapidly in tandem with the rising awareness about the benefits of solar energy. The market is moving towards renewable energy sources and clean fuels as they have minimal impact on the environment, besides being cost efficient. This is a trend both in the residential sector, and among industrial and commercial buildings.

The importance of solar charge controllers
Solar charge controllers are a must in any kind of operation of solar power systems; in fact, they act like an on and off switch. They assist power to pass when the battery requires it, and halt it when the battery is completely charged. Such a regulatory role keeps the battery healthy and ensures the device functions at an optimum level. Besides, a charge controller increases the life span of the battery by protecting it from getting overcharged by the solar arrays and over discharged by the heavy loads. Siddharth Garg, owner, Systellar Innovations, says, “A solar charge controller acts as the interface between the solar panels and batteries. There are primarily two functions of a charge controller – to properly charge the battery and to restrict the reverse charge flow from battery to solar panels during the night.” He adds that it is important that the solar charge controller’s open circuit voltage is properly matched with the solar panel array’s voltage. In the case of PWM (pulse width modulated) charge controllers, the solar panel array’s voltage is matched exactly with that of the battery bank’s voltage; however, with the MPPT (maximum power point tracking) controllers, the solar panel array’s voltage is generally kept higher than the battery bank’s voltage.

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Functionally, the charge controller receives the energy from the solar panels or the wind turbine, and converts the incoming DC voltage to the correct voltage, which is ideal for battery charging. Note that the voltage keeps fluctuating depending on the amount of sunlight the solar panels get. In bright sunlight, the voltage can go really high, which could damage the solar system. In such scenarios, the charge controller regulates the rate of the current flow in an efficient manner, regardless of the light conditions.

Current and emerging trends
There are primarily two types of solar charge controllers available in the market – PWM and MPPT. The MPPT charge controller is more in demand in the market, being much more sophisticated and advanced than the PWM variety. MPPT charge controllers are able to deliver 10-15 per cent more power from sample solar panels. Tests have proved that these controllers operate better than PWM charge controllers in cold and temperate climates. Additionally, MPPT variants can accurately identify the best working voltage and amperage of the solar panel, and match that with the electric cell bank. The outcome is 10-30 per cent more power from a sun-oriented cluster, when compared to a PWM controller. MPPT charge controllers are more costly than PWM options, but it is worth spending a little more money, considering their plus points.

To remain relevant in a fast changing market, many controllers are now available in a configurable format, whereby they can be set for a short time or for the whole night, depending on the requirements. They are also available with LED and LCD displays to communicate various parameters like battery charge levels, panel voltage, panel current, battery voltage, battery charging current, load power, etc.

A trend that may become more popular in this domain is charge controllers equipped with Bluetooth connectivity to display various performance parameters on mobile apps. Kartiga Kannan, chief technical officer, Vensai Solutions, says, “The current charge controller designs are PWM and MPPT based – and though in the future these core technologies will not change, we will get to see charge controllers with additional features like IoT enabled designs to monitor the load and battery from remote places. Also, there will be more battery de-sulfator techniques to maintain the battery capacity up to the capacity mark, a feature that we’ve already implemented in our product.”

Installation process
Before installation, it is important to familiarise oneself with certain steps and instructions to ensure the proper operation of the controllers. First, all sources of power should be disconnected from the controller. Next, a suitable surface that is even, solid, made of an incombustible substance and dry should be found to install the controller. This should be near the battery. Also, the controller should be installed in a place where casual contact is not possible. During operation, it becomes very hot and hence should be installed away from where people are. However, it should not be installed outdoors; rather, it should be kept safe from rain water, moisture, direct and indirect heat, etc.

It is important to keep an area of 15cm free on all sides of the controller to ensure air circulation for cooling. Besides, the use of insulated tools is recommended when dealing with batteries, and one should ensure no damaged cables are used. Giving more details about the process, Garg adds, “Selecting high efficiency charge controllers is also important. This will deliver a higher charge to the battery and provide longer battery backup. Also, the wire length from the solar panel to the charge controller should be kept to the minimum to avoid excess wire losses. The wire gauge for solar panel wires and battery wires should be carefully selected.” Garg says that as a thumb rule, for every 4A of current, 1 sqmm wire should be used. So, for a 40A charging current controller, a 10sqmm wire should be used. This will enhance the charging performance of the charge controller.

Maintenance and safety concerns
The maintenance of solar charge controllers does not involve any laborious tasks. They need a little care and visual inspection from time to time. They should be kept indoors in a clean and properly ventilated environment. Charge controllers with natural cooling are preferred over fan ventilated models, as dust accumulation is much higher in the case of the latter and the chances of product failure are higher. In case a charge controller is not used for a long time, its inner electrolyte capacitors tend to deteriorate. Practically, it should be used at least once or twice in a month. Apart from that, one must check that all cable connections are secure, free from terminal corrosion and cable strain. A word of caution – never attempt to open the controller or try to replace components while troubleshooting without the assistance of professionals.

Road blocks in the market
In the absence of proper regulations regarding product quality, safety and price, this market is yet to mature and become organised. Regulations are very crucial to ensure efficiency and credibility in this market, which is still fragmented and has its share of problems. There is still a lack of awareness about the quality and price of the product, and the price range varies from one place to another. As a result, domestic manufacturers have been struggling to tackle both technical and commercial problems, besides dealing with the onslaught of Chinese products. Garg points out, “Chinese models are coming into India at much cheaper prices. These are generally under rated and do not give a long performance life. Also, there is no way of getting these repaired in India, as none of the Chinese companies have service centres in India. Besides, some Chinese manufacturers are selling PWM charge controllers by claiming them to be MPPT type. This results in undercutting of prices in the Indian market and target prices become extremely low.”

Future prospects
In spite of greater adoption of solar power, some industry experts do not feel too optimistic about the sector. Garg opines that with better mains power being available these days, the requirement for solar charge controllers is reducing. Earlier, solar charge controllers were being used in households to charge inverter batteries. Now this requirement has reduced. People prefer installing grid-tied inverters for their requirements, rather than solar charge controllers with batteries.

Kannan holds a different view, saying, “The market will have plenty of requirements for DC based solar home lighting systems and solar streetlights with lithium and LFP (lithium iron phosphate) batteries in the future. It is getting more aware about these batteries, and their prices are coming down. Right now we are supplying almost 40 per cent of our charge controllers for use with lithium and LFP batteries. So these two types of batteries will ensure the solar charge controller segment booms.”

Further factors such as the steady hike in electricity rates, dropping prices of some of the key components used in the solar panels, and the gradually falling prices of industrial commodities are contributing to the growth of the solar charge controllers market. Notably, according to a report in TechSci Research, the global solar charge controller market is expected to grow at a CAGR of over 16 per cent up to 2024.

The latest products available in the market

Product: Conext MPPT 60 150 PV solar charge controller, Manufacturer: Schneider Electric
The Conext MPPT 60 150 is a photovoltaic (PV) charge controller that tracks the maximum power point of a PV array to deliver the maximum available current for charging batteries. When charging, the MPPT 60 150 regulates battery voltage and output current based on the amount of energy available from the PV array and the battery.

Key features

  • Available as a stand-alone application or fully integrated with Conext XW+ and Conext SW inverter charger systems
  • Compatible with any PV module brand
  • Remote monitoring available
  • Configurable auxiliary output
  • LCD screen with face plate buttons for configuration and system monitoring
  • Integrated PV ground fault protection for negative grounded arrays

Contact details: www.solar.schneider-electric.com

Product: PWM solar charge controller – HLS series, Manufacturer: Systellar Innovations
The HLS series of PWM charge controllers is low cost and reliable for home lighting systems. The product needs a single 12V battery and can give charging current up to 8A. The controllers in the HLS series come with a plastic body and have four DC load terminals; so multiple DC lights and fans can be connected simultaneously.
Key features

  • Microprocessor controlled zero-drop design
  • Three-stage battery charging for longer battery life
  • Selectable battery type – flat cell/tubular/SMF
  • Settable DC load operation – dusk to dawn/always on
  • Max. 50W DC load can be run continuously

Contact details: www.systellar.co.in

Product: V-SOL PWM solar charge controllers, Manufacturer: Vensai Solutions
These controllers are available to clients in customised specifications at leading markets. With an optional Wi-Fi direct connection module, one can read all the parameters any time on the mobile or laptop.

Key features

  • DC voltage: 12V/24V auto sense
  • DC current: 5 amps to 30 amps
  • Technology: PWM
  • Wi-Fi direct connection
  • Built-in dusk-to-dawn operation/normal output
  • Connections: PV battery and load

Contact details: www.vensaisolutions.in

Product: Sukam MPPT solar charge controller (25 amps, 12-24 volts), Manufacturer: Su-Kam
Su-Kam’s solar charge controllers are powered by the latest generation microprocessor and MPPT technology. The microprocessor-enabled six-stage charging ensures optimum charging of batteries, which increases their life by six months, company sources claim.

Key features

  • Connects with single and double batteries
  • Protection provided against short circuits, voltage fluctuations and wrong connections
  • LCD display for easy monitoring of the system

Contact details: www.su-kam.com

Product: Solar charge controller – SCC 1210NM, Manufacturer: Luminous India
These solar charge controllers fully charge a battery, without permitting overcharge.
Key features

  • 98 per cent efficiency
  • Inbuilt low voltage disconnect (LVD)
  • Automatic battery selection
  • USB port for DC load connection

Contact details: www.luminousindia.com

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