There are a lot of different types of batteries out there, but the most common ones used in solar systems are lead acid, lithium-ion, and nickel cadmium.
The electrolyte in these types of batteries is usually a liquid. Lead acid has been the most popular choice in off-grid systems because of their low cost, but they don’t last as long as lithium-ion or nickel cadmium batteries.
Lithium-ion batteries have high energy density and life span, which makes them ideal for solar power systems that require a lot of energy storage at once (such as those powering homes). They’re also very expensive—so it’s important to think about how much power you need before deciding whether or not Li-ion is right for your needs!
NiCad batteries have a lower energy density than either lead acid or Li-ion batteries but have longer lives than both types. Like Li-ion batteries, NiCads are also very expensive.