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Some users have noticed that solar street lights do not shine very brightly after being used for a period, especially following consecutive cloudy days when there is no sunlight. The battery voltage remains normal, and there are no faults with the controller or the light source. The issue arises from the voltage values set for the undervoltage protection mode. If this setting is too high, it results in slower recovery after an undervoltage condition, leading to the aforementioned issue. A good controller allows users to set the voltage value based on their actual conditions. So, what points should be considered when selecting a solar street light controller? Here are the tips from Century Sunshine Lighting editors.
Eight points to consider when choosing a solar street light controller:
1. Undervoltage Protection Voltage
Some users find that after solar street lights have been in operation for a while, especially after several consecutive rainy days, they can fail to light up for several days. The battery voltage is checked and found to be normal, and there are no faults with the controller or light source. This problem has puzzled many maintenance personnel. In reality, it pertains to the voltage setting for “undervoltage protection.” The higher this setting is, the longer the recovery time after an undervoltage condition, which can result in many days without proper functioning.
A good controller should allow each customer to set the undervoltage protection voltage based on their configuration. However, it is important to ensure that the solar panel configuration is reasonable. If the daily charging from the solar panels is insufficient to meet the discharge requirements through the night, the battery may frequently enter deep discharge, shortening its lifespan. Therefore, it is essential to have an ample margin with the solar panel configuration. The larger the solar panel configuration, the lower the undervoltage protection voltage can be set, thereby preventing adverse effects on the battery.
2. Constant Current Output
Due to the characteristics of LED light sources, they must be subjected to a constant current or current limiting; otherwise, their lifespan will be affected. Common solar street lights usually achieve constant current through an additional driver, which consumes a significant amount of power. Consequently, efforts have been made to integrate constant current functions within the controller itself, making installation simpler and reducing overall power consumption.
3. Output Time Period
Ordinary controllers can generally only set the light to turn on for 4 or 8 hours before shutting off, which may not meet the diverse needs of many clients. A good controller should allow for flexible setting of time periods, where each period can be set arbitrarily, and multiple on/off modes can be programmed, ideally with unique settings for each route.
4. Output Power Adjustment
Among solar-powered lighting applications, solar street lights are particularly well-suited for outputting different power levels through pulse width modulation. By limiting pulse width or current, adjustments can be made to the duty cycle of the entire output. For example, a solar street light utilizing a setup of 6 series and 5 parallel connections totaling 30W can be set to adjust power levels in late-night and early morning hours, perhaps setting it to 15W during the late night and 24W in the early morning while locking the current. This allows for all-night lighting while minimizing the costs associated with solar panels and batteries. Long-term tests have shown that solar street lights using pulse width modulation generate significantly less heat and extend the lifespan of the LEDs.
5. Heat Dissipation
Many controllers fail to consider heat dissipation to cut costs. This can lead to increased heat when current loads are high, increasing the internal resistance of the controller’s MOSFET and causing a drastic drop in charging efficiency. Overheating can severely shorten the lifespan of components or even lead to failure, particularly in high outdoor temperatures during summer. Thus, effective heat dissipation is essential for controllers. Iron or plastic casings do not meet summer heat dissipation requirements, making aluminum housing the preferred material for controller hardware.
6. MCT Charging Mode
Conventional solar controllers typically replicate the three-stage charging method of grid power chargers, which consists of constant current, constant voltage, and floating charge. This approach is feasible only for electrical grids with unlimited energy; without constant current charging, the battery could explode and be damaged. However, solar street systems have limited power from their solar panels, making it scientifically unsound to continue using the grid charger’s current limiting method. If the solar panel produces a current greater than the controller’s limitation, the charging efficiency will diminish. The MCT charging method tracks the maximum current from the solar panel, avoiding waste. By monitoring battery voltage and calculating the temperature compensation value, the system uses pulse trickle charging when the battery voltage approaches its peak, ensuring it is fully charged without overcharging.
7. Waterproof and Moisture-Proof Performance
Coastal users are often aware that a non-waterproof controller may have its circuit board corroded within six months. For maintenance convenience, most customers place controllers at the base of light poles. However, many pole manufacturers have poorly sealed bases that allow rainwater to enter, leading to potential corrosion for non-waterproof controllers. A significant influx of rainwater may cause a short circuit in the controller’s circuitry. Additionally, it is vital to wrap connections with waterproof tape, as standard insulating tapes do not guarantee that connection points remain dry.
8. Temperature Compensation Feature
This is an often-overlooked yet crucial feature. The unique negative temperature characteristic of batteries results in higher voltage at low temperatures and lower voltage at high temperatures. The controller monitors the battery voltage in real time during charging. Generally, a 12V battery will trigger protection at around 14.5V to prevent overcharging. If a controller lacks temperature compensation, significant voltage errors can occur under high or low temperatures, directly leading to problems such as an uncharged battery in low temperatures or overcharging in high temperatures.
The above points on selecting a solar street light controller are shared here. I hope this article proves helpful. If you have more questions about solar street lights, please feel free to leave a comment. We look forward to discussing with you!
