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The solar panel is equipped with a battery. How to control the charging and discharging?

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Issuing time:2019-12-30 17:14

Solar panel is a device that absorbs sunlight and directly or indirectly converts solar radiation energy into electricity through the photoelectric effect or photochemical effect. The main material of most solar panels is "silicon". Solar panels are green products that are more energy-efficient and environmentally friendly. Their main function is to generate electricity.

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How do solar panels configure batteries?


The battery charge controller is usually completed by controlling the voltage or current. Generally speaking, there are three types of battery charging methods: constant current charging, constant voltage charging, and constant power charging. Each method has different voltage and current charging characteristics.


In the charging controller of an actual photovoltaic power generation system, in order to achieve the set charging mode, the charging process must be controlled. The charging and discharging control mainly includes the determination of the charging degree, and the automatic replacement from the discharged state to the charged to charged state. Phase mode automatic conversion, stop charge control and discharge control brush. The correct control method is beneficial to improve the battery charging efficiency and service life.


The charging process is generally divided into three stages: main charging, equalizing charging and floating charging. Sometimes at the end of charging, there is trickle charging with continuous charging with a small charging current for a long time.


The main is fully fast charging and slow charging. Fast charging uses two-phase charging, three-phase charging, pulse charging, variable-current intermittent charging and variable-voltage intermittent charging. Slow charging uses a constant current with low charging current Charging mode. In order to protect the battery from overcharging, after the battery is quickly charged to 80% ~ 90% capacity, it is generally switched to floating charging (constant voltage charging) mode to adapt to the reduction of the charging current in the later stage of charging. When the floating voltage value is equal to the battery terminal voltage, the battery will automatically stop charging. To prevent possible undercharging of the battery, trickle charging can be added afterwards to make the battery cell with a fully charged battery more active. Substances participate in chemical reactions and their charging is relatively thorough.


After the lead-acid battery is deeply discharged or allowed to float for a long time, the voltage and capacity of the battery cells in series may have an imbalance. The charging to eliminate this imbalance is called balanced charging, which is referred to as uniform charging.


The solar panel is equipped with a battery. How to control the charging?


The common automatic conversion control method of each charging stage is as follows.


①Time control The charging time of each stage is set in advance, and the switching time is controlled by the time relay or CPU.


② Current and voltage control Set the threshold of charging current or battery terminal voltage. When the actual current or voltage reaches the set value, it will automatically switch.


③Capacity control The integration circuit is used to monitor the capacity of the battery online when the capacity reaches a certain value. A signal is sent to change the magnitude of the charging current.


In the above method, the time control is relatively simple, but this method lacks the information from the battery current, and the control is rough. The capacity control method has more complicated control circuits, but the control accuracy is higher.


After the battery is fully charged, the charging current must be cut off in a timely manner, otherwise overcharge reactions such as a large amount of gas escape, water loss, and temperature rise will occur in the battery, affecting the battery's service life. Therefore, the charging status of the battery must be monitored at all times to ensure that the battery is fully charged but not charged. There are four main methods of stop charging control.


① When the constant current charging method is used for timing control, the required charging time of the battery can be easily determined according to the battery capacity and the size of the charging current. Therefore, as long as the charging time is set in advance, the timer can signal to stop charging or It becomes trickle charge. This method is simple, but the charging time cannot be automatically adjusted according to the state of the battery charging surface, so it is actually charging. There may be some cases of undercharging and sometimes overcharging.


② Battery temperature control During normal charging, the temperature change of the battery is not obvious, but when the battery is overcharged, the internal gas pressure will rapidly increase, and the oxidation reaction on the negative plate will heat up the interior and the temperature will rise rapidly (per minute A few degrees Celsius). Therefore, by observing the change in battery temperature, you can determine whether the battery is fully charged. Usually two thermistors are used to monitor the battery temperature and the ambient temperature, respectively. When the temperature difference between the two reaches a certain value, a charge stop signal is issued. Due to the slow dynamic response of the thermistor, the full charge state of the battery cannot be detected in a timely and accurate manner, which is not conducive to the maintenance of the battery life.


③ Negative incremental control of battery terminal voltage When the battery is fully charged, its terminal voltage will show a downward trend. Based on this, the moment when the battery voltage has a negative increase can be used as the time to stop charging. Compared with the temperature control method, this method responds faster. In addition, the negative increase in voltage is independent of the absolute value of the voltage. Therefore, this stop charging control method can be adapted to charge battery packs with different numbers of single cells. The disadvantage of this method is that the general detector has low sensitivity and reliability. At the same time, when the ambient temperature is high, the reduction after the battery's sufficient voltage is not obvious, so it is difficult to control.


④ Using polarization voltage control Under normal circumstances, the battery's polarization voltage is generally protected between 50 and 100 mV after the battery is fully charged. Measuring the polarization voltage of each single-cell battery can make each battery charge to its own requirements Degree. Because each battery has at least some slight differences in terms of geometric structure, chemical properties, and electrical characteristics, the characteristics of each single-cell battery to determine its required charge level should be better than the battery pack as a whole. The method of control is more appropriate.


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The solar panel is equipped with a battery, how to control the discharge?


① Conventional discharge process control This control method only sets the battery over-discharge control point. When the battery voltage drops to this point, the controller disconnects the load. This control method is relatively simple, but when the battery is continuously overcast or the system is overloaded, the battery will inevitably over-discharge, and once the battery voltage reaches the over-discharge point, the system will be forced to stop working when the battery is charged. .


②Battery discharge full process control This control method controls the battery discharge according to the remaining capacity SOC of the battery, that is, in addition to setting the battery's over-discharge point SOC = 0, add several control points, SOC = 80% and SOC = 50%, etc., before the system is discharged every day, the remaining capacity of the battery on that day is detected, and then the load power or working time of the day is set according to the remaining capacity. This control method can effectively avoid overdischarge of the battery and Vicious shutdown caused by battery over-discharge.


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