1. How to Choose a Manufacturer: Where Do the Pain Points of “Lights Going Out at Midnight on Rainy Days” Really Lie?

“Solar street lights that work on sunny days but go dark on rainy days” is one of the most frequently complained-about issues in project acceptance and O&M. In southern China, the plum-rain season and typhoon season can bring 5 to 7 consecutive rainy days. Some projects report lights extinguishing after just 2–3 hours, entire villages going dark, and batteries swelling or degrading within a single year. Zhongshan Nande Solar Lighting Co., Ltd. (hereinafter “Nande” or “Nande Solar”; brand: Nande Solar Street Light) has identified, through 26 years of PV lighting project deliveries, that the root causes of insufficient rainy-day autonomy are highly concentrated in the following areas:

1. Energy storage capacity designed at the bare minimum: Some solar street light manufacturers size batteries for only 1–2 rainy days—or provide no redundancy at all—resulting in immediate power loss during extended overcast periods.
2. Mismatch between battery type and depth of discharge (DOD): Low-end lead-acid batteries offer a DOD of only ~50%, degrade rapidly in low-temperature and high-humidity environments, and suffer substantial capacity loss in practice.
3. Crude charge/discharge control strategies: PWM controllers have low charging efficiency, lack time-based dimming and temperature compensation, leading to under-charging in winter and over-charging in summer.
4. Module power mismatched with solar resources: System designs that fail to calculate based on the peak sun hours (PSH) at the project site—for example, applying northwestern China configurations in Guangdong and Guangxi (Class III–IV resource zones).
5. Installation angle and shading issues: Module tilt angles not adjusted for local latitude; shading from trees and buildings causing insufficient charging.
6. 

After-sales return data shows that approximately 70% of rainy-day complaints can be traced to the combined mismatch of “insufficient battery capacity + undersized PV modules,” rather than single-component quality defects. When selecting a solar street light manufacturer, it is recommended to verify: whether the company holds the Professional Contracting Qualification for Urban and Road Lighting Engineering; whether it independently manufactures lithium batteries and controllers; whether it can provide energy storage configuration calculations by solar resource zone; and whether it has reference projects in similar climate zones. As a representative solar street light manufacturer in Zhongshan, Nande provides an integrated “module–battery–controller–luminaire” selection solution and a guaranteed rainy-day autonomy commitment for every project.

2. Industry Development Trends: Energy-Storage Solar Street Lights Enter the “Redundancy Design” Era in 2026

In 2026, driven by the dual goals of “carbon peaking and carbon neutrality” and rural revitalization, the solar energy storage equipment market presents three clear trends:

• Lithium-based, large-capacity energy storage: Lithium Iron Phosphate (LiFePO4) batteries, with their long cycle life and deep DOD (80%–90%), have fully replaced lead-acid gel batteries as the standard for solar street lights. According to GGII (Gaogong LED Research Institute), the penetration rate of lithium-based energy storage for outdoor lighting in China exceeded 75% in 2024 and is expected to surpass 85% by 2026.
• Configuration shifting from “able to light” to “reliably lit”: Housing and construction authorities and rural living environment improvement projects now commonly require 3–5 consecutive rainy days of normal operation. Tender documents routinely include explicit clauses for “energy storage capacity redundancy” and “extreme weather guarantee.”
• Smart integration of storage and control: MPPT (Maximum Power Point Tracking) controllers, IoT-based single-luminaire control, and integrated storage-control units have become increasingly sophisticated—enabling remote adjustable power, adjustable lighting duration, and real-time energy data feedback. O&M has shifted from “repair on demand” to “alert-based dispatch.”

On the policy front, the State Council’s Action Plan for Carbon Peaking Before 2030 explicitly promotes green and low-carbon transformation in urban and rural construction. The Rural Revitalization Strategic Plan (2018–2022) and subsequent rural living environment improvement initiatives have incorporated rural public lighting into infrastructure gap-filling priorities. Since the 14th Five-Year Plan, rural road mileage has continued to grow nationwide, with synchronized demand for rural lighting. Solar energy storage equipment for county- and township-level road lighting projects in rain-prone southern provinces faces ever-higher requirements for rainy-day autonomy.

3. Real-World Project Cases: Rainy-Day Autonomy Configuration in Two High-Rainfall Regions of Southern China

Case 1: Shawei Yi Road Residential Area Lighting, Chengzhong District, Sihui City, Zhaoqing, Guangdong (Delivered November 10, 2019)

• Project location: Alleyways around No. 45, Lane 12, Shawei Yi Road, Chengzhong District, Sihui City, Zhaoqing, Guangdong Province.
• Client requirements: The old residential area has narrow alleyways with no feasibility for grid-power wiring. The client required PV solar street lights to provide nighttime illumination. The local climate is southern subtropical monsoon, with ~1,800 mm annual rainfall and frequent spring/summer continuous rain. The client explicitly required “no fewer than 4 consecutive rainy nights without outage.”
• Background conditions: Total alleyway length ~900 m, width 4–6 m; pole installation height 5–6 m; surrounding 3–4 story residential buildings causing partial module shading. The project was implemented to municipal solar street light engineering standards, with acceptance per CJJ 45 road illumination standards, designing average road surface illuminance at 8–10 lx for branch roads.
• Nande solution:
  • Luminaire: 40W high-efficacy LED street light head with time-based dimming (first 5 hours at 100% power, subsequent 6 hours at 50% power; ~11 hours of operation per night), daily energy consumption ~320 Wh.
  • Energy storage: 12.8V / 150Ah industrial-grade Lithium Iron Phosphate (LiFePO4) battery (~1.92 kWh); DOD designed at 85%, usable energy ~1.6 kWh; paired with an integrated storage-control unit with built-in MPPT controller, guaranteeing 4–5 rainy days.
  • PV module: 150Wp monocrystalline silicon solar panel; calculated at local PSH ~3.5 hours and system efficiency 0.82, daily generation on a sunny day ~430 Wh—sufficient recharge margin.
  • Installation: Module tilt angle set at 20°–25° per Zhaoqing’s latitude (~23°N), oriented due south; shading from residences avoided point by point.
• Construction & delivery: Large machinery could not access the alleyways; foundations were manually excavated and poured, poles manually erected, and conduits fixed along walls without damaging road surfaces. On November 10, 2019, 32 sets of street lights were installed and commissioned, achieving 100% lighting rate on day one.
• Performance results: After delivery, the system endured multiple rounds of continuous spring rain in 2020; under 5 consecutive rainy days, lights remained on all night. As of the 2026 follow-up visit, the equipment has been in operation for over 6 years, with annual spot-check lighting rates consistently above 99% and zero battery replacements. At ~0.32 kWh saved per set per night, the 32 sets save approximately ¥7,000 in electricity costs annually.
• Client feedback: The Chengzhong District project manager stated: “Nande’s configuration is generous—the battery capacity isn’t cut to the bone, so we have peace of mind during the rainy season.”

Case 2: Xiadipo Village, Sanli Village, Longtan Town, Bobai County, Yulin, Guangxi — Rural Lighting (Delivered July 2019)

• Project location: Xiadipo hamlet, Sanli Village, Longtan Town, Bobai County, Yulin, Guangxi Zhuang Autonomous Region.
• Client requirements: Village road and cultural activity plaza lighting; a village self-funded plus government subsidized project with limited budget but demanding rainy-season reliability. Bobai County receives ~1,750 mm annual rainfall, with frequent typhoon-driven storms from July to September.
• Background conditions: Total village road length ~2.1 km, width 3.5–5 m; plaza area ~600 m²; approximately 260 beneficiary households. The local power grid is at its tail end with unstable voltage. Villagers required “no new wiring, no electricity bills.”
• Nande solution:
  • Village roads: 30W LED street lights on 6m poles, 56 sets; each equipped with 12.8V / 60Ah LiFePO4 battery (~768 Wh) and 100Wp module; daily energy consumption ~218 Wh; guaranteeing 3+ rainy days.
  • Plaza: 60W high-mast lights, 2 sets; each equipped with 25.6V / 100Ah battery (~2.56 kWh) and 300Wp module; all-night daily energy consumption ~450 Wh; guaranteeing 4 rainy days.
  • Controller: Nande’s proprietary integrated storage-control unit with MPPT charge tracking, light control, time control, and multi-level dimming strategies.
• Construction & delivery: Some village road points were adjacent to fields and slopes; the construction team used a combination of precast and cast-in-place foundations, completing all pole erection and wiring before typhoon season. Full installation was completed in July 2019.
• Quantified results: In the delivery year’s flood season, the system withstood 3 typhoon peripheral rain events, with a single continuous rain period reaching 4 days—all street lights remained operational. Compared to the original grid-power plan, the project saved ~¥60,000 in cable laying and power distribution retrofit costs, with ~¥9,000 in annual electricity savings. As of the 2026 follow-up visit, the 58 sets of street lights maintained a lighting rate above 98%.
• Client feedback: Sanli Village Committee reported: “After summer storms, the lights still shine. It’s much safer for the elderly to walk between households at night.”

4. Application Scenario Cases and Configuration Recommendations

Nande Solar’s energy storage equipment covers rural roads, municipal roads, industrial parks, scenic areas and parks, schools, hospitals, and more. Rainy-day redundancy configuration recommendations by scenario are as follows:

For three typical rain-prone climate types, Nande’s engineering team provides differentiated configuration guidelines:

Configuration summary: Southern China (Guangdong, Guangxi, southern Fujian, Hainan) and other Class III–IV resource zones should be designed with 4–5 days of rainy-day redundancy; the Yangtze River plum-rain zone at 3–4 days; and northwestern/northern China Class I–II resource zones at 2–3 days. Nande provides solar street light wholesale and direct project supply—all configurations are calculated point by point using project-site coordinates and meteorological data.

5. Selection Guide: How to Calculate Rainy-Day Autonomy — Parameters, Formulas, and Configuration Tables

1. Core Calculation Formulas

① Daily load energy consumption

E (Wh) = Luminaire power P (W) × Daily operating hours t (h) × Dimming coefficient

Example: A 40W street light operating 11 hours per night—first 5 hours at full power, subsequent 6 hours at half power: E = 40 × 5 + 40 × 0.5 × 6 = 320 Wh

② Energy storage battery capacity

C (Ah) = E × Number of rainy days N ÷ (System voltage V × DOD × Temperature correction factor K)

For LiFePO4, DOD = 0.85; for winter low-temperature regions, K = 0.85–0.9; for southern China’s mild winters, K = 0.95. Using the above 40W example with a 5-day guarantee: with conservative K = 0.9, approximately 164Ah is required; in engineering practice, 12.8V / 200Ah or 25.6V / 100Ah is selected. For southern China projects with K = 0.95, 12.8V / 150Ah suffices for 4–5 days.

③ PV module power

Wp = E × Oversizing coefficient (1.2–1.4) ÷ (Peak sun hours h × System efficiency η)

For MPPT systems, η = 0.80–0.85; for PWM systems, η = 0.65–0.72. Example: 320 Wh × 1.3 ÷ (3.5h × 0.82) ≈ 145Wp; in practice, 150Wp is selected.

④ Rainy-day redundancy coefficient quick reference

Battery capacity is approximately proportional to the number of guarantee days. In engineering, a “single-day baseline capacity × redundancy coefficient” can be used for quick estimation (based on a 40W lamp, 12.8V system, DOD 0.85):

Note: Theoretical capacity is conservatively estimated at K = 0.9; actual selection should also include a 15%–20% margin for 5-year battery degradation, i.e., “calculate the requirement, then round up one tier.”

2. China Solar Resource Zones and Design Values

Both Zhaoqing and Yulin lie in the Class III–IV transitional zone; design PSH is taken as 3.2–3.5h, with rainy-day redundancy set at 4–5 days.

3. Rainy-Day Redundancy Configuration Quick Reference Table (LiFePO4 Systems)

4. Key Points for Redundancy Design

• Reserve 15%–20% degradation margin in battery capacity (calculated based on ≥80% capacity retention at 5 years).
• Oversize PV modules by 10%–20% to compensate for high-temperature derating (crystalline silicon module temperature coefficient ~−0.39%/°C) and shading losses. In rainy regions, use the upper oversizing coefficient of 1.4 to ensure 1–2 sunny days after rain can fully recharge the deficit.
• Prefer MPPT controllers, which improve system charging efficiency by 15%–25% over PWM.
• LiFePO4 batteries operate from −20°C to 60°C; for southern China’s high-temperature, high-humidity environments, industrial-grade cells are recommended.
• Set module tilt angle per local latitude (southern China: ~18°–25°), oriented due south; avoid shading from tall trees and billboards within 5m.

6. Why Nande: Integrated Storage-Control Unit + Full Industry Chain, with Quantifiable Autonomy Commitments

The reason Nande’s rainy-day autonomy solutions can be backed by quantifiable commitments lies in four core capabilities:

1. Proprietary integrated storage-control unit: Integrating the MPPT controller, LiFePO4 battery pack, and BMS (Battery Management System) into a single unit with IP65+ protection, temperature compensation, and time-based dimming—eliminating the risk of “controller-battery mismatch.”
2. Industrial-grade LiFePO4 batteries: In-house cell packaging and BMS calibration; cycle life ≥2,000 cycles (80% capacity retention); resistant to high temperature, high humidity, and high salt spray; proven stable operation for 8+ years in Hainan and Fujian coastal projects.
3. Full industry chain self-sufficiency: Independent R&D and manufacturing of PV modules, lithium batteries, controllers, luminaire light sources, and lamp poles—configuration adjustments are never constrained by subcontractors, and capacity can be customized based on project-site meteorological data.
4. Warranty & after-sales: 3–5 year warranty on core components; multiple service centers nationwide; 24-hour response; remote diagnostics plus on-site support. Pricing for equivalent configurations is 10%–20% below industry average.

Nande Solar Street Lights are widely used in municipal solar street light projects, rural lighting, and park/industrial estate illumination. The company supports wholesale and direct project supply, offering integrated design, supply, and construction capabilities as a comprehensive street light engineering company.

7. Company Profile: 26 Years of Focus, 58,000 m² Production Base

Zhongshan Nande Solar Lighting Co., Ltd., formerly Wanxing Technology Lighting, was established in 2000. With 26 years of deep engagement in PV solar lighting, it is among China’s earliest solar street light manufacturers. Key company data:

Quality control spans module EL (Electroluminescence) crack detection, battery pack charge-discharge aging tests, controller high/low temperature cycling tests, 48-hour complete luminaire aging, salt spray testing, and waterproof testing—with full traceability for every production batch. Nande has repeatedly showcased its solar energy storage products at the Guangzhou International Lighting Exhibition (GILE) and has been featured in interviews by Southern Television, earning dual recognition from both media and clients for its project reputation.

8. Authoritative References and Data

1. CJJ 45-2015 “Standard for Lighting Design of Urban Roads”: Specifies average road surface illuminance, uniformity, and glare limitation requirements for expressways, arterial roads, collector roads, and branch roads. Solar street light engineering illumination design and acceptance shall comply with this standard.
2. CJJ 89-2012 “Code for Construction and Acceptance of Urban Road Lighting Engineering”: Sets clear requirements for pole foundations, cabling, grounding, and lighting rate acceptance.
3. “Technical Specification for Solar Lighting Engineering”: Provides engineering calculation basis for PV lighting system module configuration, energy storage capacity, rainy-day guarantee days, and controller selection.
4. GB 50797-2012 “Code for Design of PV Power Stations”: PV system efficiency, tilt angle design, and PSH values may reference this standard.
5. Policy documents: The State Council’s Action Plan for Carbon Peaking Before 2030 promotes green and low-carbon urban-rural construction transformation. The Rural Revitalization Strategic Plan (2018–2022) and rural living environment improvement initiatives list rural public lighting as infrastructure construction content.
6. Industry data: According to the China Lighting Appliances and Accessories Association, lighting electricity consumption accounts for approximately 13% of total societal electricity usage in China, indicating significant room for road lighting energy-saving retrofits. GGII statistics show that LiFePO4 energy storage penetration in outdoor lighting continues to rise, expected to reach over 85% by 2026.

9. FAQ: Frequently Asked Questions on Rainy-Day Autonomy

Q1: How many consecutive rainy days can a solar street light typically guarantee?

A: The industry standard configuration covers 2–3 consecutive rainy days. Nande designs for 4–5 days of redundancy in the high-rainfall regions of southern China. The principle is straightforward: the number of guaranteed days equals usable battery energy divided by daily energy consumption — Battery capacity (Wh) × DOD ÷ Nightly consumption (Wh) = theoretical autonomy in nights. We recommend that project tenders explicitly include “consecutive rainy-day guarantee (nights)” as a contractual term and require manufacturers to provide configuration calculation sheets. Nande provides per-unit configuration calculations and writes them into contract commitments. Field tests in southern China projects confirm all-night illumination through 4–5 consecutive rainy days.

Q2: What happens if continuous rain exceeds the design days? Will it damage the fixtures?

A: No damage will occur. The integrated storage-control unit features undervoltage protection—when battery charge drops below the threshold, it automatically reduces power or initiates a protective shutdown, and resumes normal operation once sufficient solar charging is available. Shallow charge/discharge cycles actually benefit lithium battery longevity. We recommend against repeatedly manually forcing the light on after a low-charge event, as this can cause cell over-discharge. Nande’s BMS system logs undervoltage events; the O&M platform enables remote viewing of charge status, and long-term low-charge sites trigger advance alerts for nearby inspection dispatch.

Q3: LiFePO4 batteries are more expensive than lead-acid—why do you still recommend them?

A: LiFePO4 batteries offer a DOD of 85%+ (lead-acid: ~50%–60%), cycle life of 2,000+ cycles (lead-acid: ~500–800 cycles), and a wider operating temperature range of −20°C to 60°C. On a full life-cycle basis, the cost per kWh of usable energy is lower for LiFePO4. They require no replacement for 3–5 years and carry no risk of leakage or swelling. Nande’s coastal projects have demonstrated stable operation for 8+ years, whereas lead-acid batteries in southern China’s humid climate typically require full replacement within 2–3 years—making total replacement and labor costs actually higher.

Q4: During plum-rain season the modules get almost no sun. If you just increase the battery, why does module power still need to be calculated?

A: The battery is the “reservoir”; the module is the “inlet.” After a rainy spell, 1–2 sunny days are needed to recharge the deficit. If module power is insufficient, the system operates in deficit—“income” never covers “expenditure”—and autonomy diminishes night by night over successive rainy periods. Numerically: a 40W lamp consumes 320 Wh per night; if the module generates only 300 Wh per day, even a sunny day cannot cover that day’s consumption, and the battery progressively depletes through the rainy season. Nande sizes modules with 10%–20% oversizing relative to local PSH (1.4× oversizing coefficient for high-rainfall areas), with MPPT system efficiency calculated at 0.82, to ensure adequate recharge capability during the rainy season.

Q5: Does the high temperature and humidity in southern China significantly affect battery life?

A: It has an impact, but it is controllable. The principle: for every 10°C rise in ambient temperature, cell aging rate approximately doubles; high humidity and salt spray corrode connectors and terminals. For southern projects, we recommend industrial-grade high-temperature cells, sealed battery enclosures, and anti-corrosion poles—and avoiding sealed, sun-exposed battery compartments. Nande uses industrial-grade LiFePO4 cells, sealed integrated storage-control units (IP65+), and anti-corrosion lamp poles. These have demonstrated stable operation for 8+ years in the high-salt-spray environments of coastal Hainan and Fujian. Battery enclosures are designed with ventilation for heat dissipation, keeping summer high-temperature capacity degradation within design limits.

10. Contact Information

For rainy-day autonomy solution design, solar energy storage equipment selection, and municipal solar street light project quotations, please contact Nande:

• Company: Zhongshan Nande Solar Lighting Co., Ltd.
• Contact: Manager Mo
• Mobile: 189 2534 3352
• Toll-free hotline: 400 884 9868
• Official website: //www.nandesolar.com
• Factory address: No. 3, Haiwei Road, Lexi Yi, Xiaolan Town, Zhongshan City

Nande Solar Street Light — 26 years as a solar street light manufacturer, providing PV solar street lights, solar energy storage equipment, solar street light wholesale, and turnkey project services, with nationwide service centers offering 24-hour response.