First of all, the problem of controller is discussed. The cost ratio of controller in the whole solar street lamp system is very low, generally about 120 yuan to 200 yuan. Although it looks like a small object, it plays a great role. If it is not selected well, the stability and service life of the whole system will be greatly reduced. A relatively mature controller can also reduce the cost of the whole system through its functions, Achieve the goal of cost saving.
For the comparison of the above functions, the following analysis is made
1: Exit protection voltage
Some customers often find that after the solar street lamp has been on for a period of time, especially after continuous rainy days, the street lamp will not be on for several days or even many days. The battery voltage is normal after detection, and the controller and lamp are not faulty.
This problem has puzzled many engineers. In fact, it is a problem with the voltage value of “exiting undervoltage protection”. The higher this value is set, the longer the recovery time after undervoltage is, which leads to failure to light up for many days.
To solve this problem, the industrial controller allows each customer to set the voltage value of the exit protection according to the configuration. However, it is worth noting that the configuration of the battery panel must be reasonable. If the daily charging capacity of the battery panel cannot meet the discharge capacity of the night, the battery will often be in deep discharge and its life will be greatly shortened in the long run. Therefore, the configuration of the battery panel must enlarge the margin. The larger the configuration of the battery panel, the lower the exit protection voltage can be set, so that there will be no impact on the battery.
2: LED constant current output
Due to its own characteristics, LED must be subject to constant current or current limiting by technical means, otherwise it cannot be used normally. Common LED lamps achieve constant current of LED lamps by adding another drive power supply, but this drive accounts for about 10% – 20% of the total power of the lamp. For example, the actual power of an LED lamp with a theoretical value of 42W may be about 46-50W after being driven. When calculating the power of the battery panel and the capacity of the battery, 10% – 20% must be added to meet the power consumption caused by the drive. In addition, adding more drivers will add a fault generating link. The industrial version controller uses software to achieve constant current without power consumption, which has high stability and reduces the overall power consumption.
3: Output Period
Ordinary controllers can only be set to turn off 4 hours or 8 hours after the lights are turned on, which can no longer meet the needs of many customers. The industrial controller can be divided into three periods, and the time of each period can be set arbitrarily. Each period can be set to the off state according to the different use environment. For example, if there is no one in some factories or scenic spots at night, the second period (late at night) can be closed, or both the second and third periods can be closed to reduce the use cost.
4: LED lamp output power regulation
Among the lamps for solar energy applications, LED lamps are most suitable for achieving different power output through pulse width adjustment. At the same time of limiting pulse width or current, adjust the duty cycle of the entire output of the LED lamp. For example, a single 1W LED 7 string 5 and a total of 35W LED lamps can be discharged at night, and the power can be adjusted respectively in the late night and early morning, such as 15W in the late night and 25W in the early morning, and lock the current. This can not only meet the lighting requirements throughout the night, but also save the configuration cost of the battery board and battery. Long term tests have proved that the LED lamp with pulse width adjustment can generate much less heat and prolong the service life of the LED.
In order to save power at night, some lamp manufacturers make the interior of LED lamps into two power supplies, and turn off one power supply at night to reduce the output power by half. However, practice shows that this method will only cause half of the light sources to fail first, with inconsistent brightness or early damage of one light source.
5: Line loss compensation
The line loss compensation function is difficult to achieve with conventional controllers at present, because it requires software settings to automatically compensate according to different wire diameters and lengths. Line loss compensation is actually very important in low-voltage systems, because the voltage is low and the line loss is relatively large. If there is no corresponding line loss voltage compensation, the voltage at the output terminal may be much lower than that at the input terminal, which will result in early undervoltage protection of the battery, and the actual application rate of the battery capacity will be discounted. It is worth noting that when we use low-voltage systems, in order to reduce the line loss voltage drop, we should try not to use too thin cables, and the cables should not be too long.
6: Heat dissipation
In order to reduce the cost, many controllers do not consider the heat dissipation problem. In this way, when the load current is large or the charging current is large, the heat will increase, the internal resistance of the field tube of the controller will be increased, resulting in a significant decline in the charging efficiency, and the service life of the field tube will also be greatly reduced or even burned out after overheating. Especially, the outdoor ambient temperature is very high in summer, so a good heat dissipation device should be essential for the controller.
7: MCT charging mode
The charging mode of the conventional solar controller is the same as the three-stage charging method of the mains charger, namely constant current, constant voltage and floating charge. Because the energy of the mains power grid is infinite, if constant current charging is not carried out, the battery will be directly damaged due to charging explosion. However, the battery panel power of the solar street lamp system is limited, so it is unscientific to continue to use the constant current charging method of the mains controller. If the current generated by the battery panel is greater than the current limited by the first section of the controller, then the charging efficiency will decline. The MCT charging method is to track the maximum current of the battery panel without causing waste. By detecting the battery voltage and calculating the temperature compensation value, when the battery voltage is close to the peak value, the pulse trickle charging method is adopted to not only fully charge the battery but also prevent the battery from overcharging.