Solar panels supply high-voltage DC power to inverters and batteries connected to them. Inverter and battery are rated at a certain level which means they can handle voltage input up to a certain limit only, but DC from panels is not as per the level of these devices. Both devices are susceptible to damage from this high voltage and to prevent this solar charge controllers are used. I guess you already know about solar charge controllers, but do you know how many types of solar charge controller are there? And if you like, can I use solar panel without charge controller then you are at the right place. This article is dedicated to solar charge controller types, applications, functions, and such related information.
What is Solar Charge Controller?
A regulator for the solar battery that prevents it from overcharging is a solar charge controller. Batteries have ratings that are particularly reasonable in volts and voltage capacity. Batteries operating at a temperature or voltage more than the mentioned in their ratings reduce functionality over time and damage the batteries. Solar charge controllers are like a gateway to the battery storage system, ensuring no damage to batteries from overload or overcharge. Solar charge controllers are needed especially if you have an off-grid solar system in your home, boat, RV, or any other application, no matter how big it is.
What are Different Types of Solar Charge Controller?
Also known as solar charge regulators, they basically regulate the power supplied by solar panels before it enters the battery. Basically, there are only two types of charge controllers you have heard about, MPPT and PWM. But actually, there are 4 basic types of charge controllers that are a variation of any 1 of them. Let us discuss in brief these basic four types of solar charge controller.
1. MPPT Charge Controller
The Maximum Power Point Tracking (MPPT) solar charge controller allows the voltage from solar panels to vary from the battery voltage. With the function of varying array input, the MPPT charge controller can find the point at which there is maximum power production by solar panels. This is the most demanded solar charge controller because it effectively regulates the voltage entering the battery without actually breaking the circuit between solar panels and solar batteries. With an MPPT charge controller, voltage entering the battery will adhere to its requirements.
Maximum PowerPoint Tracking charge controllers are preferably used for negative ground systems. This is because the controller uses a negative line as a reference and then switches back to a positive line. With their ability to regulate the current supplied to the battery, it can be a multi-stage charge with bulk, absorption, and float settings. Heat dissipation is also a problem with them, especially in large solar arrays, as they are also solid state.
2. PWM Regulator
Pulse Width Modulation (PWM) regulators are more or less similar to series regulators with the only difference being that PWM regulators use a transistor to reconnect panels with the battery at high frequency. The regulator self-adjusts by varying the speed and the width (length) of the pulses sent to the battery. A PWM regulator works constantly like a rapid on/off the controller. They are also solid-state charge controllers which cannot withstand high temperatures in large solar arrays. At 100% width of the transistor solar panels charges the solar battery to the fullest but with 0% width, the transistor is off. This prevents current flow from panels to batteries. This mostly happens in the case of overvoltage supplied or when the battery is fully charged.
Transistor is placed in either line (positive or negative) that allows it to be used in both positive and negative ground systems. Some pulse width modulation regulators can be converted into series regulators for sensitive loads if they have an issue with the sound generated from PWM frequency. To maintain a constant voltage with the PWM controller, the transistor is switched at a high frequency with different modulated widths.
3. Series Regulator
Among the types of solar charge controllers are the opposite of shunt regulators as they function by opening the circuit of the solar panels after the battery reaches a set voltage. Without any charge or current flow from panels, the battery voltage will drop without any damage to the battery. After voltage drops in the battery, it connects the solar array back to the battery and current flow continues. This current flow continues from panels to batteries until it reaches the disconnect voltage. A relay or transistor is used by a series regulator to connect or disconnect solar panels with batteries.
In this solar charge controller, a relay or transistor can be placed either in positive or negative lines and some regulators can be used in both ground systems (negative and positive). They are also a type of on/off regulator and with them, batteries will either have full current or none. Duration of the current (pulse) ranges from hours to seconds depending on the state of charge (SOC) of the battery, its condition, temperature, load current, and other related factors.
4. Shunt Regulator (On/Off Regulator)
Also referred to as pulse regulators, these regulators function by short-circuiting the solar arrays as the battery reaches a set voltage. Once the battery voltage again drops, current flow from the PV array to the battery continues. It is a single-stage charge controller as it functions by Turing on or off charge regulation.
Shunt regulators generally contain a blocking diode along with a transistor. The solar array is shorted or relayed by the transistor and the blocking diode protects the battery from short circuits simultaneously. Pulse regulators are usually ideal for negatively grounded systems since the blocking diode is in the positive line. These solar charge controllers are suitable for small PV arrays. This is because they regulate the full current supplied by solar panels and during regulation it gets hot.
What is the Function of Solar Charge Controller?
The primary function of a solar charge controller is to regulate direct current (DC) power supplied by solar panels before it enters the battery, thus preventing batteries from under and overcharging. On the basis of battery voltages, various charge controllers have different set points that can be fixed or variable. Computers, dip switches, displays, jumpers, potentiometers, and other means are used to adjust variable set points. It is necessary to set the charge set point for temperature either with a remote or local temperature probe. Here is a list of functions performed by types of solar charge controller.
1. Battery Open-Circuit Protection
After the battery is normally charged, the voltage will be limited across the load to ensure that neither the load nor the battery is damaged.
2. Light Control
When used with solar lights, during daytime (good sunlight) the charge controller automatically turns off the load output. After sunset, it automatically turns on the load due to which solar lights automatically turn on at night and off in the morning.
3. Lightning Protection
During thunderstorms, the chances of lightning strike increase if your solar panels are mounted high. In case of a lightning strike, high voltage is supplied through wires that are too much to handle for battery and connected loads. Charge controllers break the circuit to prevent this high voltage from reaching the solar power system and its devices.
4. Load Short Circuit and Overcurrent Protection
Usually, solar batteries are 12V so once the load current exceeds 10A or more, the load is short-circuited. Breaking the circuit fuse blows off. That can be replaced, and your solar charge controller is good to use.
5. Overcharge and Over Discharge Protection
If the charging voltage (voltage supplied from PV panels) is higher than the protection voltage in that case, the charge controller will automatically disconnect the battery from a power source (solar panels) to prevent it from overcharging.
In case when battery voltage is lower than the protection voltage, the charge controller disconnects the battery from the load and protects it from discharge or over-discharge. After the battery is charged to an optimal level, the charge controller rejoins the connection.
6. Overvoltage Protection
The high voltage input for batteries is dangerous and can damage them. So, when the voltage is too high, solar charge controllers turn off the output automatically and prevent damage. It controls the voltage and opens the circuit when the battery voltage reaches an optimum level.
7. Reverse Battery Connection Protection
In case the polarity of the battery is reversed, charge controllers help in preventing any functionality. Once the polarity is corrected, a battery can be used.
Also See: Solar Charge Controller Settings
8. Self-Checking Function
Another function of types of solar charge controllers is that if the charge controller is not functioning properly due to internal or external factors the controller performs a self-check. Then through monitors and phone applications, charge controllers send signals and warnings to the user.
9. Temperature Compensation
Solar charge controllers monitor the temperature of the battery. If the temperature is not ideal, then it regulates the charge and discharge value making it ideal for the battery to function.
What Does Solar Controller Do When Battery Is Full?
As soon as solar batteries are fully charged, the inverter and charge controller step in. To mitigate the risks of oversupply of power to the battery, they carry out either of the following 3 functions.
- Stop the flow of current from solar panels to batteries
- Force a dump load
- Supply the incoming voltage to the connected utility grid (in the case of an on-grid solar power system).
What is Solar Charge Controller Load Output?
The total effective resistance of externally connected devices and circuits across the output terminals is known as load output. Solar charge controllers take the output from panels and feed it to the battery until it is fully charged, usually around 13.6-14.4 volts. So, in short, a solar charge controller reduces the high voltage to the optimum level to charge the battery.
A solar charge controller is rated between 6 and 60 amps and is equipped with LVD (Low Voltage Disconnect) which is usually used for small loads like lights and appliances. Small inverters should also be paired with LVD output to prevent the controller from blowing off. Some charge controllers are also equipped with sense terminals that carry very low currents around 1/10th of a mili-amp at max. With this, there is hardly any voltage drop and in case voltage drops between the battery and solar panels sense terminals raise the output to compensate for the same.
Also See: Solar Charge Controller Load Output
What are the Applications of Types of Solar Charge Controllers?
With increasing users of solar panel systems, solar charge controllers are also in high demand. Usually paired with an off-grid solar power system, a solar charge controller can be used in different applications.
- Hybrid solar power system (residential)
- Small solar power systems use Pulse Width Modulation (PWM) charge controllers.
- Solar street lamps
- Wind power turbines and small water turbines use Maximum Power Point Tracking (MPPT) charge controllers.
Also Read: 5 Different Types of Solar Mounting Structure
Can I Use Solar Panel Without Charge Controller?
Technically you can use solar panels without a charge controller and connect panels directly to the battery. But this needs to be done under specific conditions only.
1. With low-power rating solar panels you can omit the charge controller. This will not likely do any damage to the battery because its operating voltage reduces once connected to the battery.
2. Battery and panel voltage synchronize, which means panel voltage output and battery voltage input are almost the same.
3. In case you are trickling charging a battery from solar panels around 5W.
4. Use USB ports on solar panels because panels have integrated smart IC chips that regulate the voltage supplied to your device thus protecting them from over or undercharges.
If a panel emits 2 watts or fewer for every 50 battery amps-hour, then as per the general rule a charge controller is necessary. Generally, it is not advised to use solar panels without a charge controller because there are numerous risks like overvoltage, battery overcharged, and reverse current flow. All these problems occur when the output voltage from panels is not controlled. And for this, you need a charge controller. So, even if it is possible to use solar panels without a charge controller we do not recommend doing so for your personal safety.
Today you learned about what is solar charge controller, is and how many types of solar charge controller are there. I guess most people are aware of MPPT and PWM charge controllers but are not familiar with on/off pulse controllers. Now that you are well aware of different controllers along with the function of solar charge controllers you can share it further to educate people who could be potential solar power users very soon.
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