Solar LED street lights are important equipment. During use, it is essential to use solar batteries correctly. Generally, high-quality batteries can last for 3 to 4 years before needing replacement. If a new solar battery is not installed, it may lead to the solar street lights failing to illuminate properly. The lifespan of solar batteries can also be affected by certain factors. Let us examine the reasons:
1. Over-discharging or low current discharging
Over-discharging primarily occurs when the AC power supply fails, and the battery supplies power to the load for an extended period. If a battery is excessively discharged, “sulfation” occurs at the negative electrode. Since lead sulfate is an insulator, its formation will significantly impact the charging and discharging performance of the battery. The more sulfate formed at the negative electrode, the higher the internal resistance of the battery, resulting in poorer charging and discharging performance and a shortened lifespan.
2. It is very difficult to reduce lead sulfate formed under low current discharging conditions. If lead sulfate crystals are not cleaned for an extended period, it will inevitably affect the battery’s capacity and lifespan. As mentioned, over-discharging or low current discharging has a greater impact on valve-regulated batteries than on conventional batteries. Therefore, after the DC system loses AC power, it is crucial to closely monitor the battery’s voltage and current to prevent valve-regulated batteries from being over-discharged. To avoid low current discharging, valve-regulated batteries should not be left out of system operation for long periods.
3. Overcharging
Increasing the float charge voltage or raising the ambient temperature can cause the charging current to surge. The gas recombination efficiency decreases as the charging current increases; at 0.05C, the recombination rate is 90%, while it approaches zero at 0.1C. Due to overcharging, the generated gas cannot be fully recombined, resulting in increased internal pressure. Once a certain pressure is reached, the safety valve opens, releasing hydrogen and oxygen gas, along with acid mist, depleting the limited electrolyte and leading to reduced battery capacity or premature failure. Furthermore, under prolonged overcharging conditions, the increase in H+ ions raises the acidity near the positive electrode, accelerating corrosion of the grids, thinning them and hastening the battery’s deterioration, which in turn affects the battery’s lifespan.
