What kind of batteries go in solar lights?
Solar lights typically use rechargeable batteries designed for cyclic charging, with 12V lead-acid (AGM/gel) and lithium-ion (LiFePO4) being the most common. These batteries store energy from solar panels during daylight and discharge it at night for illumination. Lead-acid variants like AGM are cost-effective and robust for outdoor use, while lithium options offer higher energy density and longer lifespans. Pro Tip: Match battery voltage (e.g., 12V) to the solar light system’s specifications to avoid underperformance or damage.
Best Batteries for Outdoor Solar Lights
What battery chemistries are ideal for solar lights?
Solar lights prioritize deep-cycle durability and temperature resilience. AGM lead-acid and LiFePO4 batteries dominate due to their ability to handle daily charge-discharge cycles. For example, a 12V 20Ah AGM battery can power 10–15 LED bulbs for 8–12 hours nightly. Pro Tip: Avoid standard car batteries—they’re not designed for deep discharges and degrade quickly in solar applications.
AGM (Absorbent Glass Mat) lead-acid batteries use fiberglass mats to hold electrolytes, making them spill-proof and vibration-resistant. They tolerate temperatures from -20°C to 50°C, ideal for outdoor solar setups. Lithium iron phosphate (LiFePO4) batteries, however, provide 2000–5000 cycles versus AGM’s 500–1000, albeit at a higher upfront cost. Practically speaking, AGM suits budget-focused projects, while LiFePO4 is better for long-term installations. But what if temperatures drop below freezing? LiFePO4 retains ~80% capacity at -20°C, whereas AGM loses ~50%. Always size batteries to 1.5x daily energy needs to account for cloudy days.
| Battery Type | Cycle Life | Cost per kWh |
|---|---|---|
| AGM Lead-Acid | 500–1000 | $150–$200 |
| LiFePO4 | 2000–5000 | $400–$600 |
How do voltage and capacity affect solar light performance?
Voltage compatibility and capacity (Ah) determine runtime and reliability. A mismatch can cause undercharging or overload. For instance, a 12V system paired with a 12V 30Ah battery powers 20 LEDs for 10 hours, but a 24V battery would require a voltage converter.
Solar lights commonly operate at 12V, matching most panels and charge controllers. Capacity (measured in ampere-hours, Ah) dictates how long lights stay on. A 12V 10Ah battery stores 120Wh—enough for a 10W LED array to run 12 hours. Beyond capacity, depth of discharge (DoD) matters: discharging AGM beyond 50% drastically shortens its life, whereas LiFePO4 handles 80–90% DoD. Pro Tip: Calculate daily energy consumption (Watt-hours = LED wattage × nightly hours) and choose a battery with double that capacity to buffer cloudy days. For example, a 5W LED running 8 hours needs 40Wh; a 12V 7Ah (84Wh) battery provides a safe buffer.
Battery Expert Insight
FAQs
No—solar lights need rechargeable batteries. Standard alkaline AA cells can’t handle daily charging and may leak, damaging the fixture.
How often should solar light batteries be replaced?
AGM: 2–3 years; LiFePO4: 5–10 years. Reduced runtime or failure to hold charge signals replacement.