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A simple but "beautiful" scheme of a shunt regulator for charging batteries from a solar battery is presented. Only works on charge.

Stabilizers for solar panels very varied. The simplest type of stabilizer is shunt. 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, then up and down, that the battery is switching, then in a full current charging mode, then in a state of no charging current, and that constant switching leads to pulsed interference at the output of the stabilizer.

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

So I designed and built just such a stabilizer. You can also apply it to applications where the power of the solar panels is rather small combined with a relatively large battery capacity, or where low cost, simple design, and high reliability are more important than linear regulation 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 starts to produce 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 (it 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 14.0V, the op-amp U1 turns on the MOSFET. The transistor will shunt the solar panel (it is completely safe for it), the battery will no longer receive charge current, the indicator will turn off, the two low-power transistors will close, and the 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 works cyclically, each FET turn-on period lasts 3 seconds, and each of the battery charge periods lasts as long as necessary to reach 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 charge time of the capacitor C2 by the current, limited by the 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 sure of the correct 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 a different power consumption, you need to change the capacitance of the capacitor C2, select the bias of the transistor Q3, but maybe even this will not help to properly configure the circuit.

The MOSFET can be replaced by any transistor with a low enough on-resistance to effectively bypass the solar panel. Diode D2 can also be anything that can handle the maximum solar panel current. The use of a Schottky diode is preferable because it will drop half the voltage than a standard silicon diode, and such a diode will heat up half as much. A standard diode will fit if properly placed and mounted. 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 only necessary to replace the MOSFET transistor and the diode with more powerful ones. The rest of the circuit components will remain the same. A 4A panel control heatsink is not required. But if you put the MOSFET on a suitable heatsink, the circuit can handle a significantly more powerful panel.

Resistor R8 in this circuit is 92 kΩ, which is a non-standard value. I suggest that you use 82 kΩ and 10 kΩ resistors in series, it's easier than trying to find a custom resistor. Resistors R8, R10 and R6 determine the cutoff voltage, so it's best 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% with a digital ohmmeter.

You can also use a trimmer to adjust the voltage, but I wouldn't recommend doing this if you want to get high reliability in an aggressive environment. Trimmer resistors simply fail under such conditions.

In English.

Converting the sun's energy into electricity, have no moving parts and are therefore economical, reliable and increasingly used. There are several components in such devices, each of which performs its function.

The most "advanced" kits contain one that converts 12v DC to 220v AC. This allows you to connect conventional network devices, such as a TV and radio, to an autonomous power system.

A mandatory element necessary for the efficient operation of the entire system is a charge controller.

The main task of the charge controller is to distribute the flows of electrical energy received from the solar panel. Maintaining a stable output voltage, as well as preventing overcharging or complete discharge of the built-in system.

Thus, the service life of an expensive battery is significantly increased.

Main functions

Power system using a controller. (Click to enlarge)

The controller performs:

1. Choosing the optimal battery charge current.
2. Disconnecting the battery when charged to the set limit.

It is not necessary to buy such a controller in a specialized store. With a soldering iron and minimal knowledge in electrical engineering, you can assemble an entry-level circuit yourself.

There are several types of such devices. The simplest ones have only one function: connects and disconnects the battery depending on the level of charge.

Sophisticated devices track peak power, so they guarantee more output current, which increases system efficiency.

Each controller must comply with the following requirements:
1.2P ≤ I×U, where P is the total power of the panels; I - current at the controller output; U is the output voltage under load.

Parsing a Specific Schema

As an example, consider a hybrid power supply for emergency lighting or a system burglar alarm house, which should work around the clock.

Solar panel power during the day can not only significantly reduce electricity consumption from the network, but also protect equipment from rolling blackouts.

At night, the circuit switches to 220V power supply. The backup power source is a 12 V, 4.5 Ah rechargeable battery. Such a system will work effectively in any weather.

Diagram of a simple controller

The pinout of the transistor.

Photoresistor LDR controls transistors T1 and T2. The figure on the left shows the pinout of transistors, where E (1) is the emitter, C (2) is the collector, B (3) is the base.

During daylight hours, the photoresistor is illuminated and the transistors are closed. Therefore, 12 volt power is supplied to the battery from the panel (Solar panel) through diode D2.

It also prevents the battery from discharging through the panel. In good light, a 15W panel delivers 1A of current.

When the battery is fully charged to 11.6V, the ZD zener diode breaks through and the red LED (LED Red) lights up. When the voltage at the battery terminals drops to 11V, the LED goes out. This means that the battery needs to be charged. Resistors R1, R3 limit the current of the zener diode and LED.

At night, the resistance of the photoresistor LDR decreases, transistors T1, T2 turn on. The battery is charged through the power supply. The charging current from the 220V network through a transformer, a diode bridge D3 - D6, a resistor R4, a transistor T2 and a diode D1 goes to the battery. Capacitor C2 smooths out mains voltage ripples.

The illumination threshold at which the LDR photosensor is triggered is adjusted using a variable resistor VR1.

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

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

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

Resistor 120 kOhm.

The diode is more powerful in order to hold the current given off by the solar panel (for example, from an automobile diode bridge).

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

The relay regulator is connected to the battery, minus to the aluminum base (31k), plus to (15k), from the contact (68k), the wire through the resistor is connected to the gate of the transistor. The transistor has three legs, the first is the gate, the second is the drain, 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, then 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 a resistor closes to minus, thereby breaking the negative contact of the solar panel, and it turns off. And when the voltage drops a little, the relay-regulator will again give 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 SB wire is needed so that the battery does not discharge at night, since without light the solar panel itself consumes electricity.

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

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

Below is a not entirely clear photograph of this controller, so roughly and sloppy just all the details of the controller are fixed on the box body. The transistor heats up a little and I fixed it on a small fan. In parallel with the resistor, I put a small LED that shows the operation of the controller. When the SB is on, it is connected, when it is not, the battery is charged, and when the battery blinks quickly, the battery is almost charged and is simply being recharged.

This controller has been working for more than six months and during this time there were no problems, I connected it and that's it, now I don't monitor the battery, everything works by itself. This is my second controller, the first one I assembled for wind turbines as a ballast regulator, see about it in previous articles in the section of my homemade products.

Attention - the controller is not fully functional. After some time of operation, it turned out that the transistor in this circuit is not completely closed, and current continues to flow into the battery even if 14 volts are increased

I apologize for the non-working circuit, I myself used it for a long time and thought that everything was working, but it turns out not, and even after a full charge, current still flows into the battery. The transistor closes only halfway when it reaches 14 volts. I won’t clean up the circuit yet, as time and desire appear, I will finish this controller and lay out the working circuit.

And now I have a ballast regulator as a controller, which has been working fine 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. At the same time there are two solar panels and a wind generator on this ballast.

What are solar battery charge controllers for and what are they?

Among modern solar systems, those that work autonomously and are not connected to the electrical network have become very popular. That is, they operate in closed mode. For example, as part of the energy supply of one house. Such systems include solar panels (and / or wind generator), charge controller, inverter, relay, battery, wires. The controller in this circuit is the key element. In this article, we will talk about why you need a solar controller, what are the varieties and how to choose such a device.

As already mentioned, the charge controller is a key element of the solar system. This electronic device, based on a chip that controls the operation of the system and manages the charge of the battery. Controllers for solar panels do not allow the battery to be completely discharged and overcharged. When the battery charge is at its maximum level, the amount of current from the photocells decreases. As a result, the current necessary to compensate for self-discharge is supplied. If the battery is excessively discharged, the controller will disconnect the load from it.

So, we can summarize the functions that the solar controller performs:

• multi-stage battery charging;
• disconnection of charging or load at maximum charge or discharge, respectively;
• turn on the load when the battery charge is restored;
• automatic switching on of current from photocells for accumulator charging.

It can be concluded that such a device prolongs the life of the batteries and their breakdown.

Selection Options

What should you pay attention to when choosing a solar controller? The main features are listed below:

• Input voltage. The maximum voltage specified in the technical data sheet must be 20 percent higher than the "idle" voltage of the photocell battery. This requirement appeared due to the fact that manufacturers often set controller parameters inflated specifications. In addition, during high solar activity, the voltage may be higher than indicated in the documentation;
• Rated current. For a PWM type controller, the current rating must be 10 percent greater than the short circuit current of the battery. The MPPT type controller must be selected according to its power. Its power must be equal to or higher than the voltage of the solar system multiplied by the current of the regulator at the output. The system voltage is taken for discharged batteries. During a period of high solar activity, 20 percent in reserve should be added to the received power.

No need to skimp on this stock. After all, savings can be deplorable during a period of high solar insolation. The system can fail and the losses will be much greater.

Types of controllers

Controllers On/Off

These models are the simplest of the entire class of solar charge controllers.

On/Off models are designed to turn off battery charging when the upper voltage limit is reached. Usually it is 14.4 volts. As a result, overheating and overcharging are prevented.

The On/Off controllers will not fully charge the battery. After all, here the shutdown occurs at the moment when the maximum current is reached. And the process of charging to full capacity still needs to be maintained for several hours. The charge level at the time of shutdown is somewhere around 70 percent of the nominal capacity. Naturally, this negatively affects the condition of the battery and reduces its life.

PWM controllers

In search of a solution to incomplete battery charging in a system with On / Off devices, control units were developed based on the principle of pulse-width modulation (abbreviated as PWM) of the charging current. The meaning of the operation of such a controller is that it reduces the charging current when the voltage limit is reached. With this approach, the battery charge reaches almost 100 percent. Process efficiency increases up to 30 percent.

There are PWM models that can regulate the current depending on the OS temperature. This has a good effect on the condition of the battery, the heating decreases, the charge is better accepted. The process becomes automatic.

PWM solar charge controllers experts recommend using in regions where there is high activity sun rays. They can often be found in solar systems of low power (less than two kilowatts). As a rule, they work with batteries of small capacity.

Regulators type MPPT

MPPT charge controllers today are the most advanced devices for regulating the process of charging a battery in solar systems. These models increase the efficiency of electricity generation on the same solar panels. The principle of operation of MPPT devices is based on determining the point of maximum power value.

The MPPT continuously monitors the current and voltage in the system. Based on this data, the microprocessor calculates the optimal ratio of parameters in order to achieve maximum power output. When adjusting the voltage, even the stage of the charging process is taken into account. MPPT solar controllers even allow you to remove a large voltage from the modules, then converting it to the optimal one. The optimal one is the one that provides a full charge of the battery.

If we evaluate the operation of MPPT compared to PWM, then the efficiency of the solar system will increase from 20 to 35 percent. The pluses also include the ability to work with solar panel shading up to 40 percent. Due to the ability to maintain a high voltage value at the output of the controller, small-section wiring can be used. And you can also put the solar panels and the unit at a greater distance than in the case of PWM.

Hybrid charge controllers

In some countries, for example, the USA, Germany, Sweden, Denmark, a significant part of the electricity is generated by wind turbines. In some small countries, alternative energy takes a large share in the energy networks of these states. As part of wind systems, devices are also used to control the charging process. If the power plant is combined option from a wind generator and solar panels, then hybrid controllers are used.

These devices can be built in MPPT or PWM circuits. The main difference is that they use different current-voltage characteristics. During operation, wind generators produce very uneven power generation. As a result, the batteries receive an uneven load, and they work in a stressful mode. The task of the hybrid controller is to discharge excess energy. For this, as a rule, special heating elements are used.

If you have been thinking about an alternative way to get energy and decided to install solar panels, then you probably want to save money. One of the savings opportunities is make your own charge controller. When installing solar generators - panels, a lot of additional equipment is required: charge controllers, batteries, to transfer the current to technical standards.

Consider manufacturing do-it-yourself solar battery charge controller.

This is a device that controls the level of charge of lead-acid batteries, preventing them from being completely discharged and recharged. If the battery begins to discharge in emergency mode, the device will reduce the load and prevent complete discharge.

It is worth noting that a self-made controller cannot be compared in quality and functionality with an industrial one, but it will be quite sufficient for the operation of the electrical network. On sale come across products made in the basement, which have a very low level of reliability. If you do not have enough money for an expensive unit, it is better to assemble it yourself.

DIY solar battery charge controller

Even a homemade product must meet the following conditions:

• 1.2P< U x I , где P – общая мощность всех используемых источников напряжения, I – ток прибора на выходе, U – вольтаж системы при разряженных батареях
• The maximum allowed input voltage must be equal to the total voltage of all batteries without load.

In the image below you will see a diagram of such electrical equipment. In order to assemble it, you will need a little knowledge of electronics and a little patience. The design has been slightly modified and now a field-effect transistor is installed instead of a diode, which is regulated by a comparator.
Such a charge controller will be sufficient for use in low power networks, using only. Differs in simplicity of production and low cost of materials.

Solar charge controller It works according to a simple principle: when the voltage on the drive reaches the specified value, it stops charging, and then only the drip charge continues. If the indicator voltage drops below the set threshold, the current supply to the battery is resumed. The use of batteries is disabled by the controller when the charge in them is less than 11 V. Thanks to the operation of such a regulator, the battery will not spontaneously discharge during the absence of the sun.

Main characteristics charge controller circuits:

• Charge voltage V=13.8V (configurable), measured when there is a charge current;
• Load shedding occurs when Vbat is less than 11V (configurable);
• Turning on the load when Vbat=12.5V;
• Temperature compensation of charge mode;
• The economical TLC339 comparator can be replaced with the more common TL393 or TL339;
• The voltage drop on the keys is less than 20mV when charging with a current of 0.5A.

Advanced Solar Charge Controller

If you are confident in your knowledge of electronic equipment, you can try to assemble a more complex charge controller circuit. It is more reliable and is able to run on both solar panels and a wind generator that will help you get light in the evenings.

Above is an improved do-it-yourself charge controller circuit. To change the threshold values, tuning resistors are used, with which you will adjust the operating parameters. The current coming from the source is switched by the relay. The relay itself is controlled by a field effect transistor key.

All charge controller circuits tested in practice and have proven themselves over the course of several years.

For summer cottages and other objects where a large consumption of resources is not required, it makes no sense to spend money on expensive elements. If you have the necessary knowledge, you can modify the proposed designs or add the necessary functionality.

So you can make a charge controller with your own hands when using alternative energy devices. Do not despair if the first pancake came out lumpy. After all, no one is immune from mistakes. A little patience, diligence and experimentation will bring the matter to an end. But a working power supply will be an excellent reason for pride.