One panel is often not enough. With two, there are two ways to connect them, and the choice decides whether your station charges, charges slowly, or gets damaged.
Series: voltages add
In Series Panels chained + to -. Voltages add, current stays the same., you connect the + of one panel to the - of the next. The two free ends go to the station. The voltages add up. The current stays the same as one panel.
series: volts add, amps stay
21.5 V + 21.5 V = 43 V, at 12.4 A
Parallel: currents add
In Parallel Panels joined + to + and - to -. Currents add, voltage stays the same., you join + to + and - to -, usually with a Y-branch cable. The currents add up. The voltage stays the same as one panel.
parallel: amps add, volts stay
12.4 A + 12.4 A = 24.8 A, at 21.5 V
Which one your station can take
Take two EcoFlow NextGen 220W Bifacial Portable Solar Panels on a DELTA 3 Plus. EcoFlow's manual says to keep each input within 60 V of open-circuit voltage and 15 A of short-circuit current. In series the pair makes 43 V (about 47.1 V on a 20°F morning) and 12.4 A: inside both limits. In parallel it makes 21.5 V but 24.8 A: over the 15 A limit. Same panels, same station. One wiring works, the other does not.
The DELTA 3 Plus also has a second solar input, so a third option is one panel on each input. The checker tries every option and shows the best one first.
Inputs built for high voltage suit series strings. The BLUETTI AC200L takes up to 145 V, and BLUETTI's manual says to wire its panels in series. The EcoFlow DELTA Pro 3's High-PV input takes 30 to 150 V.
Calculator
Wire two panels
21.5 V + 21.5 V = 43 V, current stays 12.4 A
Voltage (Voc)43 Vabout 47.1 V at 20°F
Current (Isc)12.4 Aworking 11.9 A
Input limit60 V, 15 Acurrent limit is for short-circuit current (Isc)
