Lithium batteries are a more advanced technology delivering around 4,000 cycles while operating at an 80%-100% DoD. Each battery has a different type of safety certification, regarding electrolyte chemicals and the manufacturing process. Solar street lights require a battery with UL-8750 certification or a safer one.
AGM and Gel batteries are the most commonly used Lead-Acid batteries for solar street lights. Lithium-Ion (Li-Ion) batteries are among the most popular batteries for solar street lights, but also the most expensive ones. They use a lithium metal oxide cathode and a lithium-carbon anode, immersed in a lithium salt electrolyte.
To power a 12V solar street light for 12 uninterrupted hours (19:00 to 07:00) considering losses due to an 80% round-trip efficiency, a DOD of 50%, and taking 2 days of autonomy, you would require a 75Ah@12V battery for the 1,500-lumen fixture and nearly 600Ah@12V battery bank for the 12,000-lumen street light.
Most important of all, solar street lights are also helpful in evaluating the prospects for sustainability. Solar lighting systems use a solar module and a battery, wherein the system generates power throughout the day and stores it in the battery. The energy stored in the batteries comes into play at night.
The Technical Standard for Solar Street Light System, 2072 (2015) provides for technical specification for installation of solar street light systems. NOTE: Images, tables, and charts may not display correctly. Please see PDF document for full detail
Using an 80% DoD for this same battery would reduce its life to around 2,700 cycles or 7 years for solar street lights. Lithium batteries are a more advanced technology delivering around 4,000 cycles while operating at an 80%-100% DoD.