Why do 68% of solar street light failures come from poor battery choices?
Solar Street Light Battery Problems Faced by Contractors: Contractors and tradespeople frequently encounter battery issues with solar street lights, including:
- Short Lifespan/Premature Failure: Batteries often fail rapidly within one to two years, indicating an irreversible life problem.
- Cold Weather Performance Issues: In cold temperatures, batteries may malfunction, stop working entirely, or experience significantly reduced runtime.
- Incorrect Battery Sizing:
- Undersized Batteries: Using batteries with insufficient capacity leads to inadequate power supply and shorter operating times.
- Oversized Batteries: Conversely, using excessively large batteries with insufficient solar panel charging capacity results in wasted capacity.
This guide will show you how to choose lithium battery for solar street light like a professional.
Table of Contents
Critical Factors When Choosing Lithium Batteries
1. Capacity Requirements
Calculating Solar Street Light Battery Capacity: Determining Requirements Based on Power and Lighting Duration
The key to calculating the battery capacity for solar street lights lies in the power of the light fixture and the daily required lighting time.
Example of Single-Day Battery Capacity Calculation:
For instance, if a solar street light has an LED light source with an output power of 100 watts (W) and needs to illuminate for 10 hours (h) per day, then its single-day required battery capacity should be:
100W x 10h = 1000 watt-hours (Wh)
Considering Backup Capacity for Cloudy and Rainy Days:
Furthermore, to prepare for consecutive cloudy or rainy days, it’s necessary to reserve extra battery capacity as a backup. It is generally recommended to reserve a redundancy of 2-3 days. Therefore, based on the example above, the theoretical total battery capacity should be:
1000Wh x 3 days = 3000 watt-hours (Wh)
Optimization Considerations in Practical Applications:
However, in practical applications, it’s important to consider that solar street lights are often equipped with intelligent controllers. These controllers can automatically reduce the output power of the light fixture during cloudy/rainy days or when the battery power is low, thereby saving energy. Therefore, in many cases, an actual battery capacity of approximately 1.5 times the single-day capacity can meet the practical lighting needs.
2. Voltage Compatibility
Solar Street Light Battery Voltage: Matching with Solar Controllers for Optimal Performance
Ensuring the correct battery voltage is crucial for compatibility with the solar charge controller in solar lighting systems. Common system voltages include 12V and 24V.
In most solar lighting applications, particularly those with lower power requirements, 12V systems are prevalent. Examples include integrated solar street lights and solar garden lights. These systems typically have an output power of no more than 200W.
However, for higher power solar lighting systems, 24V systems offer significant efficiency advantages. This is because a 24V system operates at twice the voltage of a 12V system, resulting in only half the output current for the same power output. Since lithium batteries inherently possess internal resistance, a lower current leads to less power dissipation due to this resistance. For applications like split-type solar street lights where higher power output is desired, opting for a 24V lithium battery system is often the preferred choice for improved efficiency and performance.
3. Cycle Life & DOD
Impact of Depth of Discharge (DoD) on Solar Street Light Battery Lifespan: The DoD directly affects the lifespan of a battery. Typically, lead-acid batteries have a recommended DoD of 30-40%, while lithium batteries can achieve a DoD of up to 80%.
Nowadays, solar street lights are commonly equipped with lithium batteries. However, the cycle life of lithium batteries varies significantly depending on the battery material. This will be discussed in detail in the following chapter.
4. Temperature Range
High-Quality Lithium Solar Street Lights: Optimal Operating Temperature and Climate Considerations.
The current highest quality lithium battery solar street lights typically offer an adaptable operating temperature range of -20°C to 40°C (-4°F to 104°F). When selecting solar street lights, it is crucial to consider the local climate and environmental conditions.
The following section will provide a detailed introduction to the weather resistance and climate resilience of different lithium battery materials used in solar lighting.
5. IP Rating & Safety
Poor Water Resistance of Lithium Batteries Requires Strict IP67+ Protection
Lithium batteries generally have poor water resistance and are susceptible to water damage. Therefore, to ensure their safe and reliable operation, strict protective measures are typically required. It is recommended that the protection level reaches IP67 or higher to effectively prevent the ingress of water and dust, thereby extending the battery’s lifespan and reducing the risk of failure.
LiFePO4 vs NMC: Which Wins for Solar Lights?
In current solar lighting systems, the two main types of lithium batteries commonly used are typically: Lithium Iron Phosphate (LiFePO4) and Nickel Manganese Cobalt/Nickel Cobalt Aluminum Oxide (NMC/NCA). Both of these battery types have their own advantages and disadvantages. A detailed comparison is provided below to help you better understand their characteristics and suitable applications.
Pros and Cons Comparison
| Parameter | LiFePO4 | NMC |
|---|---|---|
| Cycle Life | 2000+ Cycles | 800-1200 Cycles |
| Low-Temperature Performance | -20°C Normal | Below 0°C Requires Heating |
| Energy Density | 120Wh/kg | 200Wh/kg |
Through comparative analysis, we have found that Lithium Iron Phosphate (LiFePO4) batteries excel in the following key aspects:
- Longer Lifespan: LiFePO4 batteries typically offer a longer cycle life compared to Nickel Manganese Cobalt (NMC) batteries, meaning they can withstand more charge and discharge cycles.
- Superior High and Low Temperature Performance: LiFePO4 batteries maintain good performance across a wider temperature range, particularly in high and low temperature environments.
- Higher Safety: Compared to NMC batteries, LiFePO4 batteries are less prone to thermal runaway in cases of overcharging or short circuits, resulting in higher safety.
However, LiFePO4 batteries also have some drawbacks:
- Lower Energy Density: For the same weight or volume, LiFePO4 batteries have a slightly lower energy storage capacity than NMC batteries.
- Larger Volume: To achieve the same capacity, LiFePO4 batteries generally require a larger volume. For example, a common LiFePO4 battery uses 32650 cells, while NMC batteries often use 18650 cells.
- Higher Cost: Despite their higher safety, the production cost of LiFePO4 batteries is typically higher than that of NMC batteries.
Scenario-Based Lithium Battery Selection Recommendations
- Applications in Extremely Cold Climates: For applications in extremely cold climate conditions, Lithium Iron Phosphate (LiFePO4) batteries are the preferred choice. LiFePO4 batteries exhibit superior performance in low-temperature environments, such as more stable discharge characteristics and higher safety, making them an ideal solution for very cold regions.
- Short-Term, Cost-Sensitive Projects: For applications with limited budgets and shorter project timelines, consider using NMC batteries to reduce upfront costs. While NMC batteries may have a shorter cycle life and potentially lower high-temperature performance compared to LiFePO4 batteries, their lower initial cost can meet the needs of short-term projects.
Safety Considerations
The Importance of BMS
The BMS (Battery Management System) is an indispensable circuit board integrated within lithium battery packs. It effectively provides comprehensive battery protection features, including:
- Overcharge Protection: Prevents the battery from being overcharged, avoiding damage.
- Over-Discharge Protection: Prevents the battery from being excessively discharged, extending its lifespan.
- Short Circuit Protection: Quickly cuts off the circuit in the event of a short circuit, preventing hazards.
- High Temperature Protection: Takes protective measures when the battery temperature becomes too high, ensuring safety.
- Battery Balancing: Ensures that each cell within the battery pack is charged and discharged evenly, improving overall performance and lifespan.
Therefore, it is strongly recommended to choose lithium batteries equipped with a BMS (Battery Management System) to ensure the safety, reliability, and long-term operation of the battery.
Lithium Battery Certification Standards
UL, CE, RoHS, and the MSDS Report Required for International Shipping.
Compatibility with Solar Systems
When integrating lithium batteries into solar systems, compatibility is crucial. Here are key considerations:
Controller Compatibility:
Ensure the Use of Controllers Supporting Lithium Battery Charging and Discharging Characteristics. This includes selecting the appropriate Pulse Width Modulation (PWM) or Maximum Power Point Tracking (MPPT) controller to optimize charging efficiency and protect the battery.
Balance Between Solar Panel Power and Battery Capacity
Optimizing Solar Charging. To avoid overcharging or insufficient power supply of lithium batteries, careful calculation and matching of solar panel power and battery capacity are necessary. A reasonable balance can maximize system performance and battery life.
Recommended Solar Battery Brands
Internationally Renowned Solar Battery Brands
Tesla Powerwall, Panasonic, LG Chem. These are leading global suppliers of residential and commercial energy storage solutions.
High-Value Solar Battery Brands
Loom Solar, Renogy, Battle Born. These brands offer reliable performance at a competitive price point, making them suitable for users with budget constraints.
Battery Procurement Channel
Alibaba B2B Platform is a major online wholesale marketplace where you can find a wide range of solar battery products and suppliers.
FAQ Section
For a 12V system, typically, the price of a LIFEP04 battery is $2 per Ah, and the price of an NMC battery is $1.37 per Ah.
To repair a solar street light with a damaged battery, you can disassemble car battery cells and weld them together in a series and parallel configuration. Please note that it is essential to remove the old battery's circuit board and weld it to the new cells, while also ensuring proper waterproofing. This can extend the lifespan of the street light.
Compared to the 3-year lifespan of lead-acid batteries, LiFePO4 batteries can last up to 10 years. However, monthly deep discharge maintenance is required.
Conclusion
This article provides an in-depth exploration of the crucial factors for lithium batteries used specifically in solar street lights. When selecting batteries for solar street lights, it is essential to comprehensively consider and balance core parameters including battery capacity, battery type, safety, and cost-effectiveness. Making an informed decision requires a careful evaluation of these key factors, ultimately leading to the selection of reliable solar street light lithium battery products or reputable brands to ensure the long-term stable operation and performance of the system.