12V, 24V, or 48V Solar Power System: Which Voltage Is Best for …
A single 100W panel can produce 20V (open circuit voltage), which is approximately 18V (optimum operating voltage), effectively charging a 12V battery bank, but not enough for a 24V battery. To charge this battery bank, you can either use a 24V (nominal) panel, or connect two smaller voltage panels in a series connection.