The charging controller software is a type of automatic charge and discharge control device installed in most solar power generation systems in order to protect the battery and prevent overcharging. Its most basic function is to cut off the charging current when the battery is full. The characteristics are different, so the charge controller used should be selected according to the battery type.
Chinese name charge controller foreign name charge controller Application field Photovoltaic power generation control field Related technology
content
1 Design requirements of charging controller software
▪ Solar panels
▪ Batteries
▪ Performance requirements
2 Overview of the control system
3 Controller Design
Design Requirements Edit Broadcast
solar panel
The solar panel is the core part of the solar photovoltaic system, and its function is to convert the radiant energy of the sun into electrical energy. Solar cells use monocrystalline silicon, polycrystalline silicon, photovoltaic thin-film cells, etc., because they are made into a P-N junction similar to a diode. Its working principle is similar to that of a diode. It’s just that it is the external electric field that drives the movement of PN junction holes and electrons in the diode, while in the solar cell, it is the solar energy that drives and affects the electron movement direction of the PN junction holes, which is commonly referred to as the “photovoltaic effect”. principle”. Electricity is generated by the directional movement of electrons driven by light energy. A solar cell is a combination of many P-N junctions in series or in parallel (in series to obtain a higher operating voltage, and in parallel to obtain a larger application current). In general, it is required to use the electric energy generated by solar energy as much as possible, so the charging circuit (when the battery power is not enough) is required to maximize the charging current, that is, the impedance of the charging circuit is minimized. Therefore, the control circuit should also adopt power tracking control.
battery charging controller software,
As an indispensable part of solar energy system accessories,
battery is a device that converts solar photovoltaic energy into chemical energy and stores it. For a 12V battery, the voltage is normally 12.4v-12.8v (gel battery reaches 13 volts). A normal lead-acid battery forms sulfuric acid crystals during discharge, and reduces to lead during charging. If the battery is often undercharged or overdischarged, or the battery is stored for a long time, it will vulcanize, and a thick and hard lead sulfate that is difficult to accept charging will form on the negative electrode. Crystallization, this phenomenon is called “irreversible sulfation” (referred to as battery vulcanization), in light vulcanization, the capacity of the battery will be reduced, the internal resistance of the battery will increase, and in severe cases, the plates will fail and be scrapped. Therefore, whether the use and maintenance of the battery is correct or not has a great impact on the service life of the battery.
Normal use should pay attention to:
1) Termination voltage: It refers to the minimum working voltage value at which the battery should not continue to discharge when the voltage drops when the battery is discharged. (The minimum operating voltage of 12V lead-acid battery is 10.5V).charging controller software.
2) Overdischarge: If the battery continues to discharge beyond the terminal voltage value of the battery discharge during the discharge process, the internal pressure of the battery may increase, the reversibility of the positive and negative electrodes, and the active material will be damaged, causing the capacity of the battery to increase.
obviously decrease
3) Overcharge: During the charging process, the voltage of the battery will gradually increase with the increase of the stored power. When the stored power of the battery reaches saturation and the electrode material cannot continue to decompose, if the battery continues to charge, the electrolyte will generate electrolysis, and in the The anode produces oxygen, and the cathode produces hydrogen. The gas will overflow from the battery, causing the electrolyte to decrease, and will cause the pressure inside the battery (especially the sealed battery) to rise, which will cause damage to the internal structure of the battery. This phenomenon is called overheating. Charging (lead-acid batteries generally allow the charging voltage not to exceed 14.5 v). In view of the above characteristics of the solar charging control system, in order to prolong the service life of the battery, a charging and discharging protection circuit must be set at the front end of the battery.
Based on the general configuration principles of solar energy, such as:
1) The solar cell power must be more than 4 times higher than the load power.
2) The capacity of the battery must be more than 6 times higher than the daily consumption of the load. Because the battery capacity is too large, the battery is always in a state of power loss, which affects the battery life.
3) The battery should be fully charged at least several times a month. The load should choose low energy consumption electrical appliances, such as LDE (Light Emitting Diode, etc.).
performance requirements
1) When the battery charging reaches the floating charge value (set to 14.5v), the controller starts the unloading current function to prevent the battery from being overcharged;charging controller software,
2) When the battery is over-discharged (10.5v), the controller starts to unload the load;
3) Any controller failure will not affect the normal operation of the beacon lights;
4) Waterproof and anti-corrosion IP76 grade;
5) The power consumption of the controller is small; the output current is large;
6) It is easy to install and can intuitively predict the current state of the battery [1].
Control System OverviewEdit Broadcast
figure 1
figure 1
The solar control system consists of solar panels, batteries, controllers and loads. The system block diagram is shown in Figure 1.
The control circuit adopts a new type of chip, which controls the on and off of the switch circuit (using Schocky diodes) by detecting and judging parameters such as solar panel voltage, battery voltage, and ambient temperature to achieve various control and protection functions. .
This solar controller has the following main functions:
1. Overcharge protection: When the charging voltage is higher than the protection voltage, the battery will be automatically turned off to charge the battery; after that, when the voltage drops to the maintenance voltage (13.sv), the battery will enter the floating state, and when the battery voltage is lower than the recovery voltage, the battery will float. Turn off the charge, enter the equalizing state, and turn off the charge when it reaches 1 4.V5.
2. Over-discharge protection; when the battery voltage is lower than the protection voltage, the controller automatically turns off the output to protect the battery from damage. When the battery is recharged, the power supply can be automatically restored.
3. Load over-current and short-circuit protection: When the load current exceeds 10A or the load is short-circuited, the power output will be automatically turned off.
4. Overvoltage protection: When the voltage is too high, the output will be automatically turned off to protect the electrical appliance from damage.
5. With anti-reverse charging function: use Schocky diode to prevent the battery from charging the solar cell.
6. It has the function of preventing lightning strikes: when there is lightning strikes, the varistor can prevent lightning strikes and protect the controller from damage.
7. Solar battery reverse connection protection: The solar battery “+” “-” polarity is reversed, it can continue to be used after correction.
8. Battery reverse connection protection.
9. Battery open circuit protection: In case of battery open circuit, if the solar battery is charged normally. The controller will limit the voltage across the load to ensure that the load is not damaged. If at night or when the solar battery is not charged, the controller will not take any action because it cannot get power by itself. 2 94 Crispy Lin Guangdong Institute of Navigation
10. With temperature compensation function
1. When the battery voltage is under normal conditions, the switch circuit controlled by the single-chip microcomputer is turned on, and the solar cell charges the battery at this time; when the battery voltage reaches 13.2v, it is in a floating state; when the battery voltage is higher than the set overcharge When the voltage reaches 14.5v, the charging circuit will be short-circuit protected and stop charging; when the battery voltage drops to 13.5v, it will resume normal charging.
2. When the battery voltage is lower than the set over-discharge point of 10.5v, the output controlled by the single-chip microcomputer is cut off, and the load has no output at this time; when the battery voltage reaches 12.4v, the single-chip computer controls the output circuit to conduct, and the load over-discharge is restored at this time. normal.
3. Display circuit. The controller uses two two-color LDE light-emitting diodes to display charging and discharging status. A red light indicates normal charging; B green light indicates that the battery is fully charged; C red light flashes indicates that the battery voltage is too low or the battery is in poor contact. The two two-color LDE LED displays are very intuitive and bring convenience to the user.
4. Temperature compensation. The capacity of the battery changes with the change of temperature. When the temperature rises, the capacity of the battery will increase, and when the temperature drops, the capacity of the battery will decrease. If the charge-discharge current remains unchanged, the corresponding charge-discharge rate will change, and different charge-discharge rates correspond to different overcharge and over-discharge points, so temperature compensation should be used to protect the battery. According to the standard temperature compensation range is -3 ~ -7mV/°C/cell, we take the middle value -5 mV/°C/cell. Since the resistance of the thermistor MF58 has an approximate linear relationship between -5 and 45 ℃, temperature compensation can be achieved. When the ambient temperature changes, the resistance of the thermistor will change with the temperature change. The single-chip microcomputer compares the sampled value with the voltage value stored in the single-chip microcomputer by sampling temperature parameters, and appropriately controls the charging voltage and discharging voltage of the battery, thereby protecting the battery.