Types of controllers for solar panels and how to choose. How to create a cheap and effective solar battery charge controller Mppt controller for solar panels with your own hands

The charge controller is a very important component of the system in which solar panels create electric current. The device controls the charging and discharging of batteries. It is thanks to him that the batteries cannot be recharged and discharged so much that it will be impossible to restore their working condition.

You can make such controllers yourself.

Homemade controller: features, components

The device is intended for operation only, which creates a current with a force of no more than 4 A. The capacity of the battery, which is charged, is 3,000 Ah.

To manufacture the controller, you need to prepare the following elements:

2 microcircuits: LM385-2.5 and TLC271 (is an operational amplifier);
3 capacitors: C1 and C2 are low-power, have 100n; C3 has a capacity of 1000u, designed for 16 V;
1 indicator LED (D1);
1 Schottky diode;
1 SB540 diode. Instead, you can use any diode, the main thing is that it can withstand the maximum current of the solar battery;
3 transistors: BUZ11 (Q1), BC548 (Q2), BC556 (Q3);
10 resistors (R1 – 1k5, R2 – 100, R3 – 68k, R4 and R5 – 10k, R6 – 220k, R7 – 100k, R8 – 92k, R9 – 10k, R10 – 92k). They can all be 5%. If you want greater accuracy, you can use 1% resistors.

How can some components be replaced?

Any of these elements can be replaced. When installing other circuits you need to think about changing the capacitance of capacitor C2 and selecting the bias of transistor Q3.

Instead of a MOSFET transistor, you can install any other one. The element must have low open channel resistance. It is better not to replace the Schottky diode. You can install a regular diode, but it must be placed correctly.

Resistors R8, R10 are equal to 92 kOhm. This value is non-standard. Because of this, such resistors are difficult to find. Their full replacement can be two resistors with 82 and 10 kOhm. They are needed switch on in series.

Read also: Features of external batteries with solar panels

If the controller will not be used in an aggressive environment, you can install a trim resistor. It allows you to control the voltage. It will not work for long in an aggressive environment.

If you need to use a controller for more powerful panels, you need to replace the MOSFET transistor and diode with more powerful analogues. All other components do not need to be changed. There is no point in installing a heatsink to regulate 4A. By installing a MOSFET on a suitable heatsink, the device will be able to work with a more efficient panel.

Principle of operation

If there is no current from the solar battery, the controller is in sleep mode. It doesn't use a single watt from the battery. After sunlight hits the panel, electric current begins to flow to the controller. It should turn on. However, the indicator LED along with 2 weak transistors turns on only when the current voltage reaches 10 V.

After reaching this voltage current will flow through the Schottky diode to the battery. If the voltage rises to 14 V, amplifier U1 will start working, which will open the MOSFET transistor. As a result, the LED will go out and two low-power transistors will close. The battery will not charge. At this time, C2 will be discharged. On average this takes 3 seconds. After capacitor C2 discharges, the hysteresis of U1 will be overcome, the MOSFET will close, and the battery will begin to charge. Charging will continue until the voltage rises to the switching level.

Charging occurs periodically. Moreover, its duration depends on the charging current of the battery and how powerful the devices connected to it are. Charging continues until the voltage reaches 14 V.

The circuit turns on in a very short time. Its activation is influenced by the charging time of C2 with current, which limits transistor Q3. The current cannot be more than 40 mA.

The operating principle of controllers for charging solar panels, the device, what to consider when choosing

In modern solar power plants, different circuits for connecting current sources are used to transfer generated electricity to working batteries. They do not use the same algorithms, are created on the basis of microprocessor technologies, and are called controllers.

How solar charge controllers work

Electricity generated by a solar battery can be transferred to storage batteries:

2. via the controller.

In the first method, electric current from the source will go to the batteries and begin to increase the voltage at their terminals. Initially, it will reach a certain limiting value, depending on the design (type) of the battery and the ambient temperature. Then it will overcome the recommended level.

At the initial stage of charging, the circuit works normally. But then extremely undesirable processes begin: the continued supply of charging current causes an increase in voltage above the permissible values (about 14 V), overcharging occurs with a sharp increase in the temperature of the electrolyte, leading to its boiling with an intense release of distilled water vapor from the elements. Sometimes until the containers dry out completely. Naturally, the battery life is sharply reduced.

Therefore, the problem of limiting the charging current is solved by controllers or manually. The last method: constantly monitoring the voltage level using instruments and switching switches by hand is so ungrateful that it exists only in theory.

Algorithms for the operation of solar battery charge controllers

Depending on the complexity of the method for limiting the maximum voltage, devices are manufactured according to the following principles:

1. Off/On (or On/Off), when the circuit simply connects the batteries to the charger according to the voltage at the terminals,

2. pulse-width (PWM) transformations,

3. scanning the maximum power point.

Principle #1: Off/On Circuit

This is the simplest, but most unreliable method. Its main disadvantage is that when the voltage at the battery terminals increases to the limit value, the capacity does not fully charge. In this case it reaches approximately 90% of the nominal value.

Batteries constantly experience a regular lack of energy, which significantly reduces their service life.

Principle No. 2: PWM controller circuit

The abbreviation for these devices in English is PWM. They are produced based on microcircuit designs. Their task is to control the power unit to regulate the voltage at its input within a given range using feedback signals.

PWM controllers can additionally:

take into account the temperature of the electrolyte using a built-in or remote sensor (the latter method is more accurate),

create temperature compensation for charging voltages,

configured for a specific type of battery (GEL, AGM, liquid acid) with different voltage graphs at the same points.

Increasing the functions of PWM controllers increases their cost and reliability.

Principle #3: Scanning the maximum power point

Such devices are designated by the English letters MPPT. They also work using the method of pulse-width converters, but they are extremely accurate because they take into account the largest amount of power that solar panels are capable of delivering. This value is always precisely defined and entered into the documentation.

For example, for 12 V solar batteries, the maximum power output point is about 17.5 V. An ordinary PWM controller will stop charging the battery when the voltage reaches 14 - 14.5 V, and one operating using MPPT technology will allow additional use of solar battery life up to 17.5 IN.

As the depth of battery discharge increases, energy losses from the source increase. MPPT controllers reduce them.

The nature of tracking the voltage corresponding to the output of the maximum power of a solar battery of 80 watts is demonstrated by the average graph.

In this way, MPPT controllers, using pulse-width conversions in all battery charging cycles, increase the output of the solar battery. Depending on various factors, savings can be 10 - 30%. In this case, the output current from the battery will exceed the input current from the solar battery.

Basic parameters of solar charge controllers

When choosing a controller for a solar battery, in addition to knowing the principles of its operation, you should pay attention to the conditions for which it is designed.

The main indicators of the devices are:

input voltage value,

the value of the total solar energy power,

nature of the connected load.

Solar battery voltage

The controller can be supplied with voltage from one or more solar panels connected in different circuits. For proper operation of the device, it is important that the total voltage supplied to it, taking into account the no-load source, does not exceed the limit value specified by the manufacturer in the technical documentation.

In this case, you should make a reserve (reserve) ≥ 20% due to a number of factors:

It’s no secret that individual parameters of a solar battery can sometimes be slightly overestimated for advertising purposes,

The processes occurring on the Sun are not stable, and during abnormally increased bursts of activity, energy transfer is possible, creating an open-circuit voltage of the solar battery above the design limit.

Solar power

It is important for choosing a controller because the device must be able to reliably transfer it to working batteries. Otherwise it will simply burn out.

To determine the power (in watts), multiply the output current from the controller (in amperes) by the voltage (in volts) generated by the solar battery, taking into account the 20% reserve created for it.

Nature of the connected load

You need to have a good understanding of the purpose of the controller. You should not use it as a universal power source by connecting various household devices to it. Of course, some of them will be able to work normally without creating anomalous conditions.

But...how long will this last? The device operates on the basis of pulse-width conversions, uses microprocessor and transistor technologies, which take into account only as a load, and not random consumers with complex transient processes during switching and the changing nature of power consumption.

Brief overview of manufacturers

Many countries are producing controllers for solar power plants. The following companies' products are popular on the Russian market:

Morningstar Corporation (leading US manufacturer),

Beijing Epsolar Technology (operating since 1990 in Beijing),

AnHui SunShine New Energy Co (PRC),

Phocos (Germany),

Steca (Germany),

Xantrex (Canada).

Among them, you can always choose a reliable controller model that is most suitable for the specific operating conditions of solar power plants with certain technical characteristics. To do this, simply use the recommendations in this article.

The controller is very simple and consists of only four parts.

This is a powerful transistor (I use IRFZ44N and can withstand current up to 49Amps).

Automotive relay-regulator with positive control (VAZ "classic").

Resistor 120 kOhm.

The diode is more powerful so that it holds the current given by the solar panel (for example, from a car diode bridge).

The operating principle is also very simple. I am writing for people who do not understand electronics at all, since I myself do not understand anything about it.

The regulator relay is connected to the battery, minus to the aluminum base (31k), plus to (15k), from the contact (68k) the wire is connected through a resistor to the gate of the transistor. The transistor has three legs, the first is the gate, the second is the drain, and the third is the source. The minus of the solar panel is connected to the source, and the plus to the battery; from the drain of the transistor, the minus of the solar panel goes to the battery.

When the relay-regulator is connected and working, the positive signal from (68k) unlocks the gate and the current from the solar panel flows through the source-drain into the battery, and when the voltage on the battery exceeds 14 volts, the relay-regulator turns off the plus and the gate of the transistor, discharging through the resistor closes to minus, thereby breaking the minus contact of the solar panel, and it turns off. And when the voltage drops a little, the relay-regulator will again apply a plus to the gate, the transistor will open and again the current from the panel will flow into the battery. A diode on the positive wire of the solar panel is needed so that the battery does not discharge at night, since without light the solar panel itself consumes electricity.

Below is a visual diagram of the connection of the controller elements.

I’m not good at electronics and maybe there are some shortcomings in my circuit, but it works without any settings and works right away, and does what factory controllers do for solar panels, and the cost is only about 200 rubles and an hour of work.

Below is a not entirely clear photo of this controller; all the parts of the controller are simply attached to the body of the box in such a rough and sloppy manner. The transistor gets a little warm and I mounted it on a small fan. I placed a small LED parallel to the resistor, which shows the operation of the controller. When it's on, the battery is connected, when it's not, it means the battery is charged, and when it's flashing quickly, the battery is almost fully charged and is just being recharged.

This controller has been working for more than six months and during this time there have been no problems, I connected it and that’s it, now I don’t monitor the battery, everything works on its own. This is my second controller, the first I assembled for wind generators as a ballast regulator, see about it in previous articles in the section on my homemade products.

Attention - the controller is not fully functional. After some time of work, it became clear that the transistor in this circuit does not completely close, and current still continues to flow into the battery even when the voltage exceeds 14 volts

I apologize for the non-working circuit, I used it for a long time and thought that everything was working, but it turns out it wasn’t, and even after being fully charged, current still flows into the battery. The transistor closes only halfway when it reaches 14 volts. I won’t remove the circuit just yet; when time and desire appear, I’ll finish this controller and post a working circuit.

And now I have a ballast regulator as a controller, which has been working perfectly for a long time. As soon as the voltage exceeds 14 volts, the transistor opens and turns on the light bulb, which burns all excess energy. There are now two solar panels and a wind generator on this ballast at the same time.

The main difficulty in using solar energy at home is its accumulation. generates electricity only when exposed to light, but you have to use electricity in the evening and at night. You cannot directly connect solar panels to batteries - both will break. Special devices are used - solar panel controllers, which can be assembled with your own hands or purchased ready-made.

Types of controllers

There are three types of solar panel controllers, differing in their functionality and price respectively.

Which one to choose

As can be seen from the descriptions, the first option (ON/OFF controller) is not at all suitable for long-term use. Those. if you have one, then you can install it to test the operation of the system, but then replace it with a PWM (PWM) controller or MTTP.

The latter is preferable. MTTP technology provides solar controller efficiency of 93-97%, while PWM provides only 65-70%. If we take into account the cost of solar panels, then the purchase of a more expensive controller is justified by the efficiency of their use.

Price

A solar power supply system is assembled primarily to save money, so the price of individual parts is a very important point. The proposed options have stood the test of time and are the optimal combination of price/quality:

Solar controller 20a link to aliexpress (opens in a new window) – cost 20,75$ - simple controls, bright LCD display, intuitive interface. Does an excellent job of charging the battery. PWM technology. It is possible to connect via USB to a computer for setup.
MPPT Tracer 2210RN Solar Charge Controller Regulator link to aliexpress (in new window), price 75$ – MTTP controller 20A – high-quality and reliable, certified, recognizes day/night. High efficiency – 97%

Video, DIY controller

You can assemble a controller for solar panels yourself, but this also requires some investment. So, to assemble a simple PWM controller you will have to spend $10 on parts and 2-3 hours of work with a soldering iron. With the cost of the finished product being $20, such a prospect no longer seems reasonable. Assembling a high-quality MPPT controller at home is generally impossible; you need both equipment and appropriate software. The video will be useful for those who love and know how to use a soldering iron.

Additions to the video: controller diagram, location of parts on the printed circuit board:

Solar battery controller circuit diagram LAY printed circuit board Location of parts on the board

Comments:

Selecting a battery for a solar power plant

Types of solar-powered garden lamps and lanterns, how and where to use them.

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A simple but “beautiful” circuit of a shunt regulator for charging batteries from a solar battery is presented. Works only on charge.

Stabilizers for solar panels are very diverse. The simplest type of stabilizer is a shunt stabilizer. It has the following advantages: simplicity, low power dissipation, low cost, high reliability.

But in exchange for these advantages, you have to put up with the fact that the voltage on the battery is constantly changing, up and down, that the battery switches between full current charging mode and no charging current state, and that constant switching leads to pulsed interference at the output of the stabilizer.

Depending on the purpose, it is necessary to select the most suitable type of stabilizer. In most solar installations I have used linear regulators, which have the advantages of smooth voltage regulation and extremely low voltage surges at the load. True, they also have significant disadvantages: higher cost, larger sizes and high power dissipation. But when I was asked to make a solar stabilizer for a yacht that served only one 3.1 amp solar panel and connected to a 300 Ah battery, it was better to use a small and simple device than a linear regulator.

So I designed and manufactured just such a stabilizer. You can also apply it to applications where the solar panel power is quite small in combination with a relatively large battery capacity, or where low cost, simple design and high reliability are more important than linear control stability.

The stabilizer was assembled on a breadboard and mounted in a sealed plastic case, which, in turn, was mounted on an aluminum mounting plate. The terminals are made of brass. This design of the device is used to withstand the harsh marine environment and rough handling.

Scheme

If the solar panel is not generating power, the entire circuit is turned off and draws absolutely no current from the battery. When the sun rises and the panel begins to output at least 10 V, the indicator LED and two low-power transistors turn on. The device starts working. As long as the battery voltage stays below 14V, the op amp (which has a very low current draw) will keep the MOSFET off so nothing much will happen and current from the solar panel will flow through the Schottky diode to the battery.

When the battery voltage reaches 14.0 V, the operational amplifier U1 will turn on the MOSFET transistor. The transistor will bypass the solar panel (this is completely safe for it), the battery will stop receiving charging current, the indicator will go out, the two low-power transistors will close, and capacitor C2 will slowly discharge. After about 3 seconds, capacitor C2 will discharge enough to overcome the hysteresis of U1, which will turn off the MOSFET again. The circuit will now charge the battery again until its voltage reaches the switching level again.

Thus, the device operates cyclically, each period of switching on the field-effect transistor lasts 3 seconds, and each of the battery charging periods lasts as long as necessary to achieve a voltage of 14.0 V. The duration of this period will vary depending on the charging current of the battery and the power of the load connected to it .

The minimum turn-on time of the circuit is determined by the time it takes for capacitor C2 to charge with a current limited by transistor Q3 to approximately 40 mA. These pulses can be very short.

Design

The design of the circuit is very simple. All components are fairly affordable, and most of them can be easily replaced with other similar components. I would not recommend replacing the TLC271 or LM385-2.5 unless you are confident in the replacement. Both of these microcircuits are low-power devices, and their consumption directly determines the turn-off time of the stabilizer. If you use microcircuits that have different power consumption, you need to change the capacitance of capacitor C2, select the bias of transistor Q3, but even this may not help configure the circuit correctly.

The MOSFET transistor can be replaced by any other transistor with a low enough on-channel resistance to effectively bypass the solar panel. Diode D2 can also be anything that can handle the maximum current of the solar panel. The use of a Schottky diode is preferable because the voltage drop across it will be half that of a standard silicon diode, and such a diode will heat up half as much. A standard diode is fine if placed and mounted correctly. With the components shown in the diagram, the stabilizer can work with solar panels with a current of up to 4 A.

For larger panels, it is necessary to replace only the MOSFET transistor and diode with more powerful ones. The remaining components of the circuit will remain the same. A radiator is not required to control a 4 A panel. But if you put the MOSFET on a suitable heat sink, the circuit can work with a significantly more powerful panel.

Resistor R8 in this circuit is 92 kOhm, which is a non-standard value. I suggest that you use 82k and 10k resistors in series, it's easier than trying to find a special resistor. Resistors R8, R10 and R6 determine the cutoff voltage, so it's better if they are accurate. I used 5% resistors, but if you want to increase the reliability of the device, use 1% resistors or select the most accurate of the 5% using a digital ohmmeter.

You can also use a trim resistor and thus regulate the voltage, but I would not recommend this if you want high reliability in a hostile environment. Trimmer resistors simply fail under such conditions.

In English.