What Are the Causes of a Solar Street Light Battery Failure?

As the core equipment of new energy outdoor lighting, solar street light is widely used in roads, parks, villages and other scenarios by virtue of the advantages of energy-saving and environmentally friendly, convenient installation and low operation and maintenance costs. As the “energy storage core” of solar street light, the battery directly determines the reliability, range and service life of the lighting system.

In recent years, the problem of solar street light battery failure has gradually come to the fore, which not only leads to insufficient lighting brightness and shortened range time, but also significantly increases the operation and maintenance costs, and even affects the return benefits of renewable energy investment. Understanding the core causes of solar street light battery failure, for early prevention, extend battery life, to ensure the stable operation of the lighting system is critical, this paper will analyze the core causes of solar street light battery failure in detail, to provide reference for relevant practitioners and users.

Battery aging

At present, the mainstream of solar street lights using lithium batteries, and lithium battery charging and discharging cycle life there are natural limitations, which is the root cause of battery aging, the so-called charging and discharging cycle life, refers to the battery from the state of discharge to the specified voltage, and then full of electricity the complete process of the number of times, the general quality of lithium batteries in the cycle life of about 1,000-2,000 times.

With the use of time, the internal chemical active material of lithium battery will be gradually depleted, resulting in a steady decline in battery performance, specifically reflected in the shrinkage of battery capacity, less and less power stored under the same light conditions, charging speed slows down, and it takes a longer time to be fully charged.

When the battery aging to a certain extent, there will be obvious signs of failure, such as LED street lamp lighting time significantly shortened, originally 10 hours of continuous lighting, aging may only be able to maintain 5 hours, lighting brightness is unstable, there are bright and dim, and ultimately will completely lose the ability to store electricity, resulting in street lamps can not be normally lit.

Overcharging and discharging

The hazards of overcharging

When the charging system of solar street light fails to effectively control the charging voltage and current, it will lead to overcharging of the battery, and during the process of overcharging, a large amount of heat will be generated inside the battery, which cannot be emitted in time, and it will accelerate the decomposition of the internal electrolyte and the depletion of electrode materials, which not only reduces the performance of the battery, but also causes bulging, liquid leakage, and even short-circuit damage to the battery in case of serious damage.

Common triggering factors

The appearance of solar street light overcharge and discharge, more related to the external environment and system configuration, such as strong light time solar panel power generation suddenly increased, if the charge controller does not respond in time, it may trigger overcharging, continuous cloudy and rainy weather light is not enough, the battery continues to discharge for street lighting, easy to lead to overdischarge, in addition to the charging controller parameter setting is not appropriate, the system is incorrectly wired, etc., will increase the risk of over-charging. In addition, improper setting of charge controller parameters, system wiring errors, etc., will also increase the risk of overcharge and discharge.

Environmental factors

Impact of extreme temperature

High temperature environment will accelerate the chemical reaction speed inside the battery, leading to electrolyte decomposition, electrode corrosion, and at the same time reduce the thermal stability of the battery, increasing the potential safety hazards. Low temperature environment will slow down the ion migration inside the battery, the battery charging and discharging efficiency and capacity will be significantly reduced, for example, below - 10 ℃, the capacity of lithium batteries may only be 60% -70% of the normal temperature, and charging difficulty increases dramatically.

Humidity and other environmental stress

High humidity environment, water is easy to penetrate into the interior of the LED street light, triggering corrosion of the internal components, which in turn leads to battery short-circuit, liquid leakage and other failures, in addition to outdoor dust, rain scouring, seasonal temperature changes, etc., but also indirectly affects the sealing of the battery and the stability of the internal structure, to accelerate the occurrence of failures.

Charging system failure

Solar panel failure

Solar panel is the core of solar street light energy collection, if it is damaged or degraded due to external impact, aging, excessive dust accumulation, etc., it will directly reduce the power generation, for example, the surface of the solar panel is covered with a large amount of dust, which reduces the transmittance of the solar panels, and the power generation may be reduced by more than 30%, and solar panels are not properly mounted at an appropriate angle, which can not adequately receive light, and it will also lead to insufficient charging, and the battery is in a state of power loss for a long time. The battery will be in a state of power loss for a long time, accelerating aging.

Charge controller failure

Charge controller is the “core hub” for regulating charging and discharging, responsible for controlling charging voltage and current, preventing overcharging and over discharging of the battery. If the charge controller has problems such as damage of electronic components, program failure, etc., it will lose the regulating function, which may lead to overcharging and over discharging of the battery, or it may directly not be able to charge the battery.

Battery management system (BMS) defects

BMS is mainly responsible for monitoring the voltage, current, temperature and other parameters of street light batteries to protect the batteries, if there are design defects or failures in the BMS, it cannot monitor the abnormal state of the batteries in a timely manner, which will keep the batteries in an unsafe operating environment for a long time and increase the risk of failure.

Materials and manufacturing quality

Impact of poor quality materials

If poor quality lithium battery cells, electrolyte or casing materials are used, the stability and durability of the battery will be significantly reduced, for example, the charging/discharging cycle life of poor quality cells may only be 50% of that of high quality cells, poor quality electrolyte is easy to decompose, which will accelerate the battery's internal loss, and the casing materials are poorly sealed, which will easily lead to the infiltration of water.

Manufacturing process defects

During the battery production process, if the assembly process is rough and the quality control is not strict, there may be problems such as loose internal wiring, irregular arrangement of cells, poor sealing performance, etc. These hidden problems may not be obvious at the initial stage, but they will be exposed gradually in long-term use, leading to battery leakage, short circuit, rapid capacity degradation and other failures.

The long-term risk of poor-quality batteries is significant, not only the use of solar street light life is short, may be used only 1-2 years after the failure, far lower than the service life of high-quality batteries 5-8 years, but also increase the frequency and cost of operation and maintenance, frequent replacement of batteries will significantly increase the total cost of ownership of the solar street light system.

Improper maintenance

Lack of regular cleaning

If the battery surface and surrounding components accumulate dust, debris or bird droppings for a long period of time, it will directly affect the heat dissipation effect of the battery, especially in the high temperature of the summer, the accumulation of heat will keep the battery in a long term high temperature operation state, accelerating the aging speed of the internal chemical substances.

At the same time, dust and debris into the battery wiring port, but also cause port oxidation, increasing contact resistance, affecting the charging and discharging efficiency, and corrosive bird droppings residue will destroy the sealing of the battery shell, so that moisture is more likely to penetrate the interior, and ultimately triggered by the solar energy LED street light internal short circuit or electrolyte leakage and other serious failures.

Damaged parts are not replaced in time

When the wires, connectors, sealing tape and other key parts around the solar street light battery are worn, aged and broken, if they are not replaced in time, it will bring a series of chain reactions to the solar street light system.Broken wires will leak due to the insulation layer falling off, which will continue to consume the solar street light battery power, resulting in a significant decrease in the range of solar street light. The aging connector will lose its fastening effect, further aggravating the loosening problem of the battery connection part and affecting the charging stability. Cracked sealing tape will completely destroy the waterproof and dust proof performance of the solar street light battery, allowing outdoor rain and dust to easily invade the interior of the solar street light battery.

These problems may not directly lead to the initial solar street light battery failure, but will continue to erode the core components of the battery, significantly shorten the normal service life of the solar street light battery, and ultimately let the solar street light battery failure in advance, affecting the normal lighting function of the solar street light.